Fix publish action

.github/workflows/analyze-and-test.yaml

@@ -10,7 +10,7 @@ jobs:
     name: Flutter analyze
     strategy:
       matrix:
-        flutter: ['stable', 'dev']
+        flutter: ['beta']
     runs-on: macos-latest
     steps:
       - uses: actions/checkout@v2

.github/workflows/publish-on-pub.yaml

@@ -10,12 +10,11 @@ jobs:
       - uses: actions/checkout@v2
       - uses: subosito/flutter-action@v1
         with:
-          channel: 'stable'
+          channel: 'beta'
       - run: flutter pub get
       - run: flutter pub run tool/publish/comment_dependency_overrides.dart
       - run: flutter pub get
-      - run: echo ::set-env name=RELEASE_VERSION::${GITHUB_REF}
-      - run: flutter pub run tool/publish/check_version.dart ${{ env.RELEASE_VERSION }}
+      - run: flutter pub run tool/publish/check_version.dart ${GITHUB_REF}
       - name: Setup credentials
         run: |
           mkdir -p $FLUTTER_HOME/.pub-cache

CHANGELOG.md

@@ -1,3 +1,12 @@
+## [0.7.1]
+- Fix a crash for some lottie file with empty paths.
+
+## [0.7.0+1]
+- Fix Flutter Web compilation error
+
+## [0.7.0]
+- Performance improvement for complex animations.
+
 ## [0.6.0]
 - Runs the animation at the frame rate specified in the json file (ie. An animation encoded with a 20 FPS will only
   be paint 20 times per seconds even though the AnimationController will invalidate the widget 60 times per seconds).  

README.md

@@ -8,7 +8,7 @@ animations exported as json with [Bodymovin](https://github.com/airbnb/lottie-we
 
 This repository is a unofficial conversion of the [Lottie-android](https://github.com/airbnb/lottie-android) library in pure Dart. 
 
-It works on Android, iOS and macOS and web.
+It works on Android, iOS, macOS, linux, windows and web.
 
 ## Usage
 
@@ -64,7 +64,7 @@ class MyApp extends StatefulWidget {
 }
 
 class _MyAppState extends State<MyApp> with TickerProviderStateMixin {
-  AnimationController _controller;
+  late final AnimationController _controller;
 
   @override
   void initState() {
@@ -137,7 +137,7 @@ class MyWidget extends StatefulWidget {
 }
 
 class _MyWidgetState extends State<MyWidget> {
-  Future<LottieComposition> _composition;
+  late final Future<LottieComposition> _composition;
 
   @override
   void initState() {
@@ -176,7 +176,7 @@ a specific position and size.
 class CustomDrawer extends StatelessWidget {
   final LottieComposition composition;
 
-  const CustomDrawer(this.composition, {Key key}) : super(key: key);
+  const CustomDrawer(this.composition, {Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

README.template.md

@@ -8,7 +8,7 @@ animations exported as json with [Bodymovin](https://github.com/airbnb/lottie-we
 
 This repository is a unofficial conversion of the [Lottie-android](https://github.com/airbnb/lottie-android) library in pure Dart. 
 
-It works on Android, iOS and macOS and web.
+It works on Android, iOS, macOS, linux, windows and web.
 
 ## Usage
 

example/lib/examples/alert_dialog.dart

@@ -23,7 +23,7 @@ class __PageState extends State<_Page> {
   void initState() {
     super.initState();
 
-    SchedulerBinding.instance.addPostFrameCallback((_) => _showLoader());
+    SchedulerBinding.instance!.addPostFrameCallback((_) => _showLoader());
   }
 
   void _showLoader() {

example/lib/examples/animate_no_repeat.dart

@@ -6,7 +6,7 @@ void main() async {
 }
 
 class App extends StatelessWidget {
-  const App({Key key}) : super(key: key);
+  const App({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

example/lib/examples/animation_controller.dart

@@ -9,7 +9,7 @@ class MyApp extends StatefulWidget {
 }
 
 class _MyAppState extends State<MyApp> with TickerProviderStateMixin {
-  AnimationController _controller;
+  late final AnimationController _controller;
 
   @override
   void initState() {

example/lib/examples/animation_full_control.dart

@@ -17,7 +17,7 @@ class MyApp extends StatefulWidget {
 }
 
 class _MyAppState extends State<MyApp> with TickerProviderStateMixin {
-  AnimationController _controller;
+  late final AnimationController _controller;
 
   @override
   void initState() {
@@ -97,7 +97,7 @@ class _MyAppState extends State<MyApp> with TickerProviderStateMixin {
                   min: start,
                   max: stop,
                   reverse: true,
-                  period: _controller.duration * (stop - start),
+                  period: _controller.duration! * (stop - start),
                 );
               },
             ),

example/lib/examples/custom_draw.dart

@@ -22,7 +22,7 @@ class MyWidget extends StatefulWidget {
 }
 
 class _MyWidgetState extends State<MyWidget> {
-  Future<LottieComposition> _composition;
+  late final Future<LottieComposition> _composition;
 
   @override
   void initState() {
@@ -57,7 +57,7 @@ class _MyWidgetState extends State<MyWidget> {
 class CustomDrawer extends StatelessWidget {
   final LottieComposition composition;
 
-  const CustomDrawer(this.composition, {Key key}) : super(key: key);
+  const CustomDrawer(this.composition, {Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

example/lib/examples/custom_load.dart

@@ -23,7 +23,7 @@ class MyWidget extends StatefulWidget {
 }
 
 class _MyWidgetState extends State<MyWidget> {
-  Future<LottieComposition> _composition;
+  late final Future<LottieComposition> _composition;
 
   @override
   void initState() {

example/lib/examples/dynamic_properties.dart

@@ -8,7 +8,7 @@ void main() async {
 }
 
 class App extends StatefulWidget {
-  const App({Key key}) : super(key: key);
+  const App({Key? key}) : super(key: key);
 
   @override
   _AppState createState() => _AppState();
@@ -50,7 +50,7 @@ class _AppState extends State<App> with TickerProviderStateMixin {
               value: _useDelegates,
               onChanged: (newValue) {
                 setState(() {
-                  _useDelegates = newValue;
+                  _useDelegates = newValue!;
                 });
               },
             ),

example/lib/examples/dynamic_text.dart

@@ -7,14 +7,14 @@ void main() async {
 }
 
 class App extends StatefulWidget {
-  const App({Key key}) : super(key: key);
+  const App({Key? key}) : super(key: key);
 
   @override
   _AppState createState() => _AppState();
 }
 
 class _AppState extends State<App> with TickerProviderStateMixin {
-  TextEditingController _textController;
+  late final TextEditingController _textController;
 
   @override
   void initState() {

example/lib/examples/hide_after_complete.dart

@@ -6,14 +6,14 @@ void main() async {
 }
 
 class App extends StatefulWidget {
-  const App({Key key}) : super(key: key);
+  const App({Key? key}) : super(key: key);
 
   @override
   _AppState createState() => _AppState();
 }
 
 class _AppState extends State<App> with TickerProviderStateMixin {
-  AnimationController _animationController;
+  late final AnimationController _animationController;
   bool _showAnimation = true;
 
   @override

example/lib/examples/markers.dart

@@ -9,14 +9,14 @@ void main() async {
 }
 
 class App extends StatefulWidget {
-  const App({Key key}) : super(key: key);
+  const App({Key? key}) : super(key: key);
 
   @override
   _AppState createState() => _AppState();
 }
 
 class _AppState extends State<App> with TickerProviderStateMixin {
-  Future<LottieComposition> _composition;
+  late final Future<LottieComposition> _composition;
 
   @override
   void initState() {
@@ -35,9 +35,9 @@ class _AppState extends State<App> with TickerProviderStateMixin {
         body: FutureBuilder<LottieComposition>(
           future: _composition,
           builder: (context, snapshot) {
-            if (snapshot.hasError) return ErrorWidget(snapshot.error);
+            if (snapshot.hasError) return ErrorWidget(snapshot.error!);
             if (!snapshot.hasData) return CircularProgressIndicator();
-            return _LottieDetails(snapshot.data);
+            return _LottieDetails(snapshot.data!);
           },
         ),
       ),
@@ -48,7 +48,7 @@ class _AppState extends State<App> with TickerProviderStateMixin {
 class _LottieDetails extends StatefulWidget {
   final LottieComposition composition;
 
-  const _LottieDetails(this.composition, {Key key}) : super(key: key);
+  const _LottieDetails(this.composition, {Key? key}) : super(key: key);
 
   @override
   _LottieDetailsState createState() => _LottieDetailsState();
@@ -56,7 +56,7 @@ class _LottieDetails extends StatefulWidget {
 
 class _LottieDetailsState extends State<_LottieDetails>
     with TickerProviderStateMixin {
-  AnimationController _controller;
+  late final AnimationController _controller;
 
   @override
   void initState() {
@@ -112,8 +112,8 @@ class _LottieDetailsState extends State<_LottieDetails>
   }
 
   void _playBetween(String marker1, String marker2) {
-    var start = widget.composition.getMarker(marker1).start;
-    var end = widget.composition.getMarker(marker2).start;
+    var start = widget.composition.getMarker(marker1)!.start;
+    var end = widget.composition.getMarker(marker2)!.start;
 
     _controller.value = start;
     _controller.animateTo(end,

example/lib/examples/repeat.dart

@@ -0,0 +1,63 @@
+import 'package:flutter/material.dart';
+import 'package:lottie/lottie.dart';
+
+void main() => runApp(MyApp());
+
+class MyApp extends StatefulWidget {
+  @override
+  _MyAppState createState() => _MyAppState();
+}
+
+class _MyAppState extends State<MyApp> with TickerProviderStateMixin {
+  late final AnimationController _controller;
+  int _repeatIndex = 0;
+
+  @override
+  void initState() {
+    super.initState();
+
+    _controller = AnimationController(vsync: this)
+      ..addStatusListener((status) {
+        if (status == AnimationStatus.completed) {
+          setState(() {
+            _repeatIndex++;
+          });
+          if (_repeatIndex < 5) {
+            _controller.reset();
+            _controller.forward();
+          }
+        }
+      });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      home: Scaffold(
+        body: ListView(
+          children: [
+            Lottie.asset(
+              'assets/AndroidWave.json',
+              controller: _controller,
+              width: 150,
+              height: 150,
+              onLoaded: (composition) {
+                // Configure the AnimationController with the duration of the
+                // Lottie file and start the animation.
+                _controller.duration = composition.duration;
+                _controller.forward();
+              },
+            ),
+            Center(child: Text('Repeat: $_repeatIndex')),
+          ],
+        ),
+      ),
+    );
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+}

example/lib/examples/run_once.dart

@@ -12,7 +12,7 @@ void main() async {
 }
 
 class App extends StatefulWidget {
-  const App({Key key}) : super(key: key);
+  const App({Key? key}) : super(key: key);
 
   @override
   _AppState createState() => _AppState();
@@ -20,7 +20,7 @@ class App extends StatefulWidget {
 
 class _AppState extends State<App> with TickerProviderStateMixin {
   int _index = 0;
-  AnimationController _animationController;
+  late final AnimationController _animationController;
 
   @override
   void initState() {

example/lib/examples/save_frames.dart

@@ -1,3 +1,5 @@
+//@dart=2.10
+
 import 'dart:io';
 import 'dart:ui';
 import 'package:flutter/material.dart';

example/lib/main_app.dart

@@ -42,7 +42,9 @@ class App extends StatelessWidget {
                 ),
               ),
               onTap: () {
-                Navigator.of(context).push(MaterialPageRoute<void>(
+                Navigator.push(
+                    context,
+                    MaterialPageRoute<void>(
                         builder: (context) => Detail(assetName)));
               },
             );
@@ -56,7 +58,7 @@ class App extends StatelessWidget {
 class _Item extends StatelessWidget {
   final Widget child;
 
-  const _Item({Key key, this.child}) : super(key: key);
+  const _Item({Key? key, required this.child}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
@@ -81,26 +83,18 @@ class _Item extends StatelessWidget {
 class Detail extends StatefulWidget {
   final String assetName;
 
-  const Detail(this.assetName, {Key key}) : super(key: key);
+  const Detail(this.assetName, {Key? key}) : super(key: key);
 
   @override
   _DetailState createState() => _DetailState();
 }
 
 class _DetailState extends State<Detail> with TickerProviderStateMixin {
-  AnimationController _controller;
-
-  @override
-  void initState() {
-    super.initState();
-
-    _controller = AnimationController(vsync: this);
-  }
+  late final _controller = AnimationController(vsync: this);
 
   @override
   void dispose() {
     _controller.dispose();
-
     super.dispose();
   }
 

example/lib/sizing_example.dart

@@ -13,7 +13,7 @@ void main() async {
 class App extends StatelessWidget {
   final LottieComposition composition;
 
-  const App({Key key, this.composition}) : super(key: key);
+  const App({Key? key, required this.composition}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
@@ -97,13 +97,13 @@ class App extends StatelessWidget {
 
 class _Lottie extends StatefulWidget {
   final LottieComposition composition;
-  final double width;
-  final double height;
-  final BoxFit fit;
-  final AlignmentGeometry alignment;
+  final double? width;
+  final double? height;
+  final BoxFit? fit;
+  final AlignmentGeometry? alignment;
 
   const _Lottie(this.composition,
-      {Key key, this.width, this.height, this.fit, this.alignment})
+      {Key? key, this.width, this.height, this.fit, this.alignment})
       : super(key: key);
 
   @override
@@ -111,7 +111,7 @@ class _Lottie extends StatefulWidget {
 }
 
 class __LottieState extends State<_Lottie> with TickerProviderStateMixin {
-  AnimationController _controller;
+  late AnimationController _controller;
 
   @override
   void initState() {

example/lib/tests/airbnb.dart

@@ -6,7 +6,7 @@ void main() async {
 }
 
 class App extends StatelessWidget {
-  const App({Key key}) : super(key: key);
+  const App({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

example/lib/tests/we_accept.dart

@@ -6,7 +6,7 @@ void main() async {
 }
 
 class App extends StatelessWidget {
-  const App({Key key}) : super(key: key);
+  const App({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

example/macos/Podfile.lock

@@ -24,4 +24,4 @@ SPEC CHECKSUMS:
 
 PODFILE CHECKSUM: d8ba9b3e9e93c62c74a660b46c6fcb09f03991a7
 
-COCOAPODS: 1.9.1
+COCOAPODS: 1.10.0

example/macos/Runner.xcodeproj/project.pbxproj

@@ -330,10 +330,10 @@
 			buildActionMask = 2147483647;
 			files = (
 			);
-			inputFileListPaths = (
+			inputPaths = (
 			);
 			name = "[CP] Embed Pods Frameworks";
-			outputFileListPaths = (
+			outputPaths = (
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;

example/pubspec.lock

@@ -7,77 +7,70 @@ packages:
       name: archive
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.13"
-  args:
-    dependency: transitive
-    description:
-      name: args
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.6.0"
+    version: "3.0.0-nullsafety.0"
   async:
     dependency: transitive
     description:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.2"
+    version: "2.5.0-nullsafety.3"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.0-nullsafety.3"
   characters:
     dependency: transitive
     description:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.0"
+    version: "1.1.0-nullsafety.5"
   charcode:
     dependency: transitive
     description:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.3"
+    version: "1.2.0-nullsafety.3"
   clock:
     dependency: transitive
     description:
       name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.1"
+    version: "1.1.0-nullsafety.3"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.13"
-  convert:
-    dependency: transitive
-    description:
-      name: convert
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.1.1"
+    version: "1.15.0-nullsafety.5"
   crypto:
     dependency: transitive
     description:
       name: crypto
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.5"
+    version: "3.0.0-nullsafety.0"
   fake_async:
     dependency: transitive
     description:
       name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.2.0-nullsafety.3"
+  ffi:
+    dependency: transitive
+    description:
+      name: ffi
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.1.3"
   file:
     dependency: transitive
     description:
@@ -96,7 +89,7 @@ packages:
       name: flutter_colorpicker
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.3.4"
+    version: "0.4.0-nullsafety.0"
   flutter_test:
     dependency: "direct dev"
     description: flutter
@@ -108,7 +101,7 @@ packages:
       name: golden_toolkit
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.6.0"
+    version: "0.9.0-nullsafety.0"
   http:
     dependency: "direct main"
     description:
@@ -136,42 +129,42 @@ packages:
       name: logging
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.11.4"
+    version: "1.0.0-nullsafety.0"
   lottie:
     dependency: "direct main"
     description:
       path: ".."
       relative: true
     source: path
-    version: "0.6.0"
+    version: "0.8.0-nullsafety.0"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.8"
+    version: "0.12.10-nullsafety.3"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.8"
+    version: "1.3.0-nullsafety.6"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.7.0"
+    version: "1.8.0-nullsafety.3"
   path_provider:
     dependency: "direct main"
     description:
       name: path_provider
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.6.14"
+    version: "1.6.27"
   path_provider_linux:
     dependency: transitive
     description:
@@ -185,21 +178,28 @@ packages:
       name: path_provider_macos
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.4+3"
+    version: "0.0.4+8"
   path_provider_platform_interface:
     dependency: transitive
     description:
       name: path_provider_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.3"
+    version: "1.0.4"
+  path_provider_windows:
+    dependency: transitive
+    description:
+      name: path_provider_windows
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.0.4+3"
   pedantic:
     dependency: transitive
     description:
       name: pedantic
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.0"
+    version: "1.9.2"
   platform:
     dependency: transitive
     description:
@@ -213,7 +213,7 @@ packages:
       name: plugin_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.2"
+    version: "1.0.3"
   process:
     dependency: transitive
     description:
@@ -232,63 +232,70 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.7.0"
+    version: "1.8.0-nullsafety.4"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.5"
+    version: "1.10.0-nullsafety.6"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.0-nullsafety.3"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.5"
+    version: "1.1.0-nullsafety.3"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.2.0-nullsafety.3"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.17"
+    version: "0.2.19-nullsafety.6"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.3.0-nullsafety.5"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.8"
+    version: "2.1.0-nullsafety.5"
+  win32:
+    dependency: transitive
+    description:
+      name: win32
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.7.4"
   xdg_directories:
     dependency: transitive
     description:
       name: xdg_directories
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.0"
+    version: "0.1.2"
 sdks:
-  dart: ">=2.9.0-14.0.dev <3.0.0"
-  flutter: ">=1.12.13+hotfix.5 <2.0.0"
+  dart: ">=2.12.0-29.10.beta <3.0.0"
+  flutter: ">=1.24.0-10.2.pre <2.0.0"

example/pubspec.yaml

@@ -1,23 +1,23 @@
 name: lottie_example
 description: A sample app for the Lottie player
-version: 0.0.1
+publish_to: none
 
 environment:
-  sdk: ">=2.7.0 <3.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   flutter:
     sdk: flutter
+  flutter_colorpicker: ^0.4.0-nullsafety.0
+  http:
   lottie:
     path: ../
-  flutter_colorpicker:
   path_provider:
-  http:
 
 dev_dependencies:
   flutter_test:
     sdk: flutter
-  golden_toolkit:
+  golden_toolkit: ^0.9.0-nullsafety.0
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec
@@ -31,6 +31,7 @@ flutter:
     - assets/lottiefiles/
     - assets/Mobilo/
     - assets/Tests/
+    - assets/Tests/images/
     - assets/Logo/
     - assets/Images/
     - assets/Images/WeAccept/

example/test/dynamic_properties_test.dart

@@ -7,7 +7,7 @@ import 'package:lottie/lottie.dart';
 import 'utils.dart';
 
 void main() {
-  LottieComposition composition;
+  late LottieComposition composition;
 
   setUpAll(() async {
     composition = await LottieComposition.fromBytes(
@@ -15,7 +15,7 @@ void main() {
   });
 
   void testGolden(String description, ValueDelegate delegate,
-      {double progress}) async {
+      {double? progress}) async {
     var screenshotName = description
         .toLowerCase()
         .replaceAll(RegExp('[^a-z0-9 ]'), '')
@@ -288,8 +288,8 @@ void main() {
     testGolden(
         'Opacity interpolation ($progress)',
         ValueDelegate.transformOpacity(['Shape Layer 1', 'Rectangle'],
-            callback: (frameInfo) => lerpDouble(
-                    10, 100, Curves.linear.transform(frameInfo.overallProgress))
+            callback: (frameInfo) => lerpDouble(10, 100,
+                    Curves.linear.transform(frameInfo.overallProgress))!
                 .round()),
         progress: progress);
   }

example/test/flutter_test_config.dart

@@ -1,7 +1,7 @@
 import 'dart:async';
 import 'package:golden_toolkit/golden_toolkit.dart';
 
-Future<void> main(FutureOr<void> Function() testMain) async {
+Future<void> testExecutable(FutureOr<void> Function() testMain) async {
   await loadAppFonts();
   return testMain();
 }

example/test/golden_test.dart

@@ -16,7 +16,8 @@ void main() {
       var size = Size(500, 400);
       tester.binding.window.physicalSizeTestValue = size;
       tester.binding.window.devicePixelRatioTestValue = 1.0;
-      var composition = await tester.runAsync(() => FileLottie(asset).load());
+      var composition =
+          (await tester.runAsync(() => FileLottie(asset).load()))!;
 
       await tester.pumpWidget(FilmStrip(composition, size: size));
 

example/test/utils.dart

@@ -3,11 +3,11 @@ import 'package:lottie/lottie.dart';
 
 class FilmStrip extends StatelessWidget {
   final LottieComposition composition;
-  final LottieDelegates delegates;
+  final LottieDelegates? delegates;
   final Size size;
 
   const FilmStrip(this.composition,
-      {Key key, @required this.size, this.delegates})
+      {Key? key, required this.size, this.delegates})
       : super(key: key);
 
   @override

lib/src/animation/content/base_stroke_content.dart

@@ -34,21 +34,20 @@ abstract class BaseStrokeContent
   final List<double> _dashPatternValues;
   final Paint paint = Paint()..style = PaintingStyle.stroke;
 
-  final BaseKeyframeAnimation<dynamic, double> _widthAnimation;
-  final BaseKeyframeAnimation<dynamic, int> _opacityAnimation;
-  final List<BaseKeyframeAnimation<dynamic, double>> _dashPatternAnimations;
-  final BaseKeyframeAnimation<dynamic,
-      double> /*?*/ _dashPatternOffsetAnimation;
-  BaseKeyframeAnimation<ColorFilter, ColorFilter> /*?*/ _colorFilterAnimation;
+  final BaseKeyframeAnimation<Object, double> _widthAnimation;
+  final BaseKeyframeAnimation<Object, int> _opacityAnimation;
+  final List<BaseKeyframeAnimation<Object, double>> _dashPatternAnimations;
+  final BaseKeyframeAnimation<Object, double>? _dashPatternOffsetAnimation;
+  BaseKeyframeAnimation<ColorFilter, ColorFilter?>? _colorFilterAnimation;
 
   BaseStrokeContent(this.lottieDrawable, this.layer,
-      {StrokeCap cap,
-      StrokeJoin join,
-      double miterLimit,
-      AnimatableIntegerValue opacity,
-      AnimatableDoubleValue width,
-      List<AnimatableDoubleValue> dashPattern,
-      AnimatableDoubleValue dashOffset})
+      {required StrokeCap cap,
+      required StrokeJoin join,
+      required double miterLimit,
+      required AnimatableIntegerValue opacity,
+      required AnimatableDoubleValue width,
+      required List<AnimatableDoubleValue> dashPattern,
+      AnimatableDoubleValue? dashOffset})
       : _widthAnimation = width.createAnimation(),
         _opacityAnimation = opacity.createAnimation(),
         _dashPatternOffsetAnimation = dashOffset?.createAnimation(),
@@ -76,7 +75,7 @@ abstract class BaseStrokeContent
       _dashPatternAnimations[i].addUpdateListener(onUpdateListener);
     }
     if (_dashPatternOffsetAnimation != null) {
-      _dashPatternOffsetAnimation.addUpdateListener(onUpdateListener);
+      _dashPatternOffsetAnimation!.addUpdateListener(onUpdateListener);
     }
   }
 
@@ -86,7 +85,7 @@ abstract class BaseStrokeContent
 
   @override
   void setContents(List<Content> contentsBefore, List<Content> contentsAfter) {
-    TrimPathContent trimPathContentBefore;
+    TrimPathContent? trimPathContentBefore;
     for (var i = contentsBefore.length - 1; i >= 0; i--) {
       var content = contentsBefore[i];
       if (content is TrimPathContent &&
@@ -98,7 +97,7 @@ abstract class BaseStrokeContent
       trimPathContentBefore.addListener(onUpdateListener);
     }
 
-    _PathGroup currentPathGroup;
+    _PathGroup? currentPathGroup;
     for (var i = contentsAfter.length - 1; i >= 0; i--) {
       var content = contentsAfter[i];
       if (content is TrimPathContent &&
@@ -119,7 +118,8 @@ abstract class BaseStrokeContent
   }
 
   @override
-  void draw(Canvas canvas, Size size, Matrix4 parentMatrix, {int parentAlpha}) {
+  void draw(Canvas canvas, Size size, Matrix4 parentMatrix,
+      {required int parentAlpha}) {
     L.beginSection('StrokeContent#draw');
     if (parentMatrix.hasZeroScaleAxis) {
       L.endSection('StrokeContent#draw');
@@ -136,7 +136,7 @@ abstract class BaseStrokeContent
     }
 
     if (_colorFilterAnimation != null) {
-      paint.colorFilter = _colorFilterAnimation.value;
+      paint.colorFilter = _colorFilterAnimation!.value;
     }
 
     for (var i = 0; i < _pathGroups.length; i++) {
@@ -175,18 +175,17 @@ abstract class BaseStrokeContent
     var pathMetrics = _path.computeMetrics().toList();
     var totalLength = pathMetrics.fold<double>(0.0, (a, b) => a + b.length);
 
-    var offsetLength = totalLength * pathGroup.trimPath.offset.value / 360.0;
-    var startLength =
-        totalLength * pathGroup.trimPath.start.value / 100.0 + offsetLength;
-    var endLength =
-        totalLength * pathGroup.trimPath.end.value / 100.0 + offsetLength;
+    var trimPath = pathGroup.trimPath!;
+    var offsetLength = totalLength * trimPath.offset.value / 360.0;
+    var startLength = totalLength * trimPath.start.value / 100.0 + offsetLength;
+    var endLength = totalLength * trimPath.end.value / 100.0 + offsetLength;
 
     var currentLength = 0.0;
     for (var j = pathGroup.paths.length - 1; j >= 0; j--) {
       _trimPathPath
           .set(pathGroup.paths[j].getPath().transform(parentMatrix.storage));
       var pathMetrics = _trimPathPath.computeMetrics().toList();
-      var length = pathMetrics.first.length;
+      var length = pathMetrics.isNotEmpty ? pathMetrics.first.length : 0;
       if (endLength > totalLength &&
           endLength - totalLength < currentLength + length &&
           currentLength < endLength - totalLength) {
@@ -229,7 +228,7 @@ abstract class BaseStrokeContent
   }
 
   @override
-  Rect getBounds(Matrix4 parentMatrix, {bool applyParents}) {
+  Rect getBounds(Matrix4 parentMatrix, {required bool applyParents}) {
     L.beginSection('StrokeContent#getBounds');
     _path.reset();
     for (var i = 0; i < _pathGroups.length; i++) {
@@ -279,7 +278,7 @@ abstract class BaseStrokeContent
 
     var offset = _dashPatternOffsetAnimation == null
         ? 0.0
-        : _dashPatternOffsetAnimation.value * scale;
+        : _dashPatternOffsetAnimation!.value * scale;
     var newPath = dashPath(path, intervals: _dashPatternValues, phase: offset);
     L.endSection('StrokeContent#applyDashPattern');
 
@@ -295,7 +294,7 @@ abstract class BaseStrokeContent
 
   @override
   @mustCallSuper
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     if (property == LottieProperty.opacity) {
       _opacityAnimation.setValueCallback(callback as LottieValueCallback<int>);
     } else if (property == LottieProperty.strokeWidth) {
@@ -309,9 +308,9 @@ abstract class BaseStrokeContent
         _colorFilterAnimation = null;
       } else {
         _colorFilterAnimation =
-            ValueCallbackKeyframeAnimation<ColorFilter, ColorFilter>(
-                callback as LottieValueCallback<ColorFilter>);
-        _colorFilterAnimation.addUpdateListener(onUpdateListener);
+            ValueCallbackKeyframeAnimation<ColorFilter, ColorFilter?>(
+                callback as LottieValueCallback<ColorFilter>, null);
+        _colorFilterAnimation!.addUpdateListener(onUpdateListener);
         layer.addAnimation(_colorFilterAnimation);
       }
     }
@@ -321,7 +320,7 @@ abstract class BaseStrokeContent
 /// Data class to help drawing trim paths individually.
 class _PathGroup {
   final List<PathContent> paths = <PathContent>[];
-  final TrimPathContent /*?*/ trimPath;
+  final TrimPathContent? trimPath;
 
   _PathGroup(this.trimPath);
 }

lib/src/animation/content/content.dart

@@ -1,5 +1,5 @@
 abstract class Content {
-  String get name;
+  String? get name;
 
   void setContents(List<Content> contentsBefore, List<Content> contentsAfter);
 }

lib/src/animation/content/content_group.dart

@@ -1,5 +1,4 @@
 import 'dart:ui';
-import 'package:meta/meta.dart';
 import 'package:vector_math/vector_math_64.dart';
 import '../../lottie_drawable.dart';
 import '../../model/animatable/animatable_transform.dart';
@@ -32,8 +31,7 @@ class ContentGroup implements DrawingContent, PathContent, KeyPathElement {
     return contents;
   }
 
-  static AnimatableTransform /*?*/ findTransform(
-      List<ContentModel> contentModels) {
+  static AnimatableTransform? findTransform(List<ContentModel> contentModels) {
     for (var i = 0; i < contentModels.length; i++) {
       var contentModel = contentModels[i];
       if (contentModel is AnimatableTransform) {
@@ -47,12 +45,12 @@ class ContentGroup implements DrawingContent, PathContent, KeyPathElement {
   final Path _path = PathFactory.create();
 
   @override
-  final String name;
+  final String? name;
   final bool _hidden;
   final List<Content> _contents;
   final LottieDrawable _lottieDrawable;
-  List<PathContent> /*?*/ _pathContents;
-  TransformKeyframeAnimation /*?*/ _transformAnimation;
+  List<PathContent>? _pathContents;
+  TransformKeyframeAnimation? _transformAnimation;
 
   ContentGroup(final LottieDrawable lottieDrawable, BaseLayer layer,
       ShapeGroup shapeGroup)
@@ -65,11 +63,11 @@ class ContentGroup implements DrawingContent, PathContent, KeyPathElement {
             findTransform(shapeGroup.items));
 
   ContentGroup.copy(this._lottieDrawable, BaseLayer layer, this.name,
-      this._hidden, this._contents, AnimatableTransform /*?*/ transform) {
+      this._hidden, this._contents, AnimatableTransform? transform) {
     if (transform != null) {
-      _transformAnimation = transform.createAnimation();
-      _transformAnimation.addAnimationsToLayer(layer);
-      _transformAnimation.addListener(onValueChanged);
+      _transformAnimation = transform.createAnimation()
+        ..addAnimationsToLayer(layer)
+        ..addListener(onValueChanged);
     }
 
     var greedyContents = <GreedyContent>[];
@@ -104,20 +102,20 @@ class ContentGroup implements DrawingContent, PathContent, KeyPathElement {
 
   List<PathContent> getPathList() {
     if (_pathContents == null) {
-      _pathContents = <PathContent>[];
+      var pathContents = _pathContents = <PathContent>[];
       for (var i = 0; i < _contents.length; i++) {
         var content = _contents[i];
         if (content is PathContent) {
-          _pathContents.add(content);
+          pathContents.add(content);
         }
       }
     }
-    return _pathContents;
+    return _pathContents!;
   }
 
   Matrix4 getTransformationMatrix() {
     if (_transformAnimation != null) {
-      return _transformAnimation.getMatrix();
+      return _transformAnimation!.getMatrix();
     }
     _matrix.reset();
     return _matrix;
@@ -128,7 +126,7 @@ class ContentGroup implements DrawingContent, PathContent, KeyPathElement {
     // TODO: cache this somehow.
     _matrix.reset();
     if (_transformAnimation != null) {
-      _matrix.set(_transformAnimation.getMatrix());
+      _matrix.set(_transformAnimation!.getMatrix());
     }
     _path.reset();
     if (_hidden) {
@@ -145,17 +143,17 @@ class ContentGroup implements DrawingContent, PathContent, KeyPathElement {
 
   @override
   void draw(Canvas canvas, Size size, Matrix4 parentMatrix,
-      {@required int parentAlpha}) {
+      {required int parentAlpha}) {
     if (_hidden) {
       return;
     }
     _matrix.set(parentMatrix);
     int layerAlpha;
     if (_transformAnimation != null) {
-      _matrix.preConcat(_transformAnimation.getMatrix());
-      var opacity = _transformAnimation.opacity == null
+      _matrix.preConcat(_transformAnimation!.getMatrix());
+      var opacity = _transformAnimation?.opacity == null
           ? 100
-          : _transformAnimation.opacity.value;
+          : _transformAnimation!.opacity!.value;
       layerAlpha = ((opacity / 100.0 * parentAlpha / 255.0) * 255).round();
     } else {
       layerAlpha = parentAlpha;
@@ -199,10 +197,10 @@ class ContentGroup implements DrawingContent, PathContent, KeyPathElement {
   }
 
   @override
-  Rect getBounds(Matrix4 parentMatrix, {bool applyParents}) {
+  Rect getBounds(Matrix4 parentMatrix, {required bool applyParents}) {
     _matrix.set(parentMatrix);
     if (_transformAnimation != null) {
-      _matrix.preConcat(_transformAnimation.getMatrix());
+      _matrix.preConcat(_transformAnimation!.getMatrix());
     }
     var bounds = Rect.zero;
     for (var i = _contents.length - 1; i >= 0; i--) {
@@ -223,8 +221,8 @@ class ContentGroup implements DrawingContent, PathContent, KeyPathElement {
       return;
     }
 
-    if ('__container' != name) {
-      currentPartialKeyPath = currentPartialKeyPath.addKey(name);
+    if ('__container' != name && name != null) {
+      currentPartialKeyPath = currentPartialKeyPath.addKey(name!);
 
       if (keyPath.fullyResolvesTo(name, depth)) {
         accumulator.add(currentPartialKeyPath.resolve(this));
@@ -245,9 +243,9 @@ class ContentGroup implements DrawingContent, PathContent, KeyPathElement {
   }
 
   @override
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     if (_transformAnimation != null) {
-      _transformAnimation.applyValueCallback(property, callback);
+      _transformAnimation!.applyValueCallback(property, callback);
     }
   }
 }

lib/src/animation/content/drawing_content.dart

@@ -1,10 +1,9 @@
 import 'dart:ui';
-import 'package:meta/meta.dart';
 import 'package:vector_math/vector_math_64.dart';
 import 'content.dart';
 
 abstract class DrawingContent extends Content {
   void draw(Canvas canvas, Size canvasSize, Matrix4 parentMatrix,
-      {@required int parentAlpha});
-  Rect getBounds(Matrix4 parentMatrix, {@required bool applyParents});
+      {required int parentAlpha});
+  Rect getBounds(Matrix4 parentMatrix, {required bool applyParents});
 }

lib/src/animation/content/ellipse_content.dart

@@ -22,10 +22,10 @@ class EllipseContent implements PathContent, KeyPathElementContent {
   final Path _path = PathFactory.create();
 
   @override
-  final String name;
+  final String? name;
   final LottieDrawable lottieDrawable;
-  final BaseKeyframeAnimation<dynamic, Offset> _sizeAnimation;
-  final BaseKeyframeAnimation<dynamic, Offset> _positionAnimation;
+  final BaseKeyframeAnimation<Object, Offset> _sizeAnimation;
+  final BaseKeyframeAnimation<Object, Offset> _positionAnimation;
   final CircleShape _circleShape;
 
   final CompoundTrimPathContent _trimPaths = CompoundTrimPathContent();
@@ -115,7 +115,7 @@ class EllipseContent implements PathContent, KeyPathElementContent {
   }
 
   @override
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     if (property == LottieProperty.ellipseSize) {
       _sizeAnimation.setValueCallback(callback as LottieValueCallback<Offset>);
     } else if (property == LottieProperty.position) {

lib/src/animation/content/fill_content.dart

@@ -22,12 +22,12 @@ class FillContent implements DrawingContent, KeyPathElementContent {
   final Paint _paint = Paint();
   final BaseLayer layer;
   @override
-  final String name;
+  final String? name;
   final bool _hidden;
   final List<PathContent> _paths = <PathContent>[];
-  BaseKeyframeAnimation<Color, Color> _colorAnimation;
-  BaseKeyframeAnimation<int, int> _opacityAnimation;
-  BaseKeyframeAnimation<ColorFilter, ColorFilter> /*?*/ _colorFilterAnimation;
+  late final BaseKeyframeAnimation<Color, Color> _colorAnimation;
+  late final BaseKeyframeAnimation<int, int> _opacityAnimation;
+  BaseKeyframeAnimation<ColorFilter, ColorFilter?>? _colorFilterAnimation;
   final LottieDrawable lottieDrawable;
 
   FillContent(this.lottieDrawable, this.layer, ShapeFill fill)
@@ -39,10 +39,10 @@ class FillContent implements DrawingContent, KeyPathElementContent {
 
     _path.fillType = fill.fillType;
 
-    _colorAnimation = fill.color.createAnimation();
+    _colorAnimation = fill.color!.createAnimation();
     _colorAnimation.addUpdateListener(onValueChanged);
     layer.addAnimation(_colorAnimation);
-    _opacityAnimation = fill.opacity.createAnimation();
+    _opacityAnimation = fill.opacity!.createAnimation();
     _opacityAnimation.addUpdateListener(onValueChanged);
     layer.addAnimation(_opacityAnimation);
   }
@@ -62,7 +62,8 @@ class FillContent implements DrawingContent, KeyPathElementContent {
   }
 
   @override
-  void draw(Canvas canvas, Size size, Matrix4 parentMatrix, {int parentAlpha}) {
+  void draw(Canvas canvas, Size size, Matrix4 parentMatrix,
+      {required int parentAlpha}) {
     if (_hidden) {
       return;
     }
@@ -76,7 +77,7 @@ class FillContent implements DrawingContent, KeyPathElementContent {
     }
 
     if (_colorFilterAnimation != null) {
-      _paint.colorFilter = _colorFilterAnimation.value;
+      _paint.colorFilter = _colorFilterAnimation!.value;
     }
 
     _path.reset();
@@ -93,7 +94,7 @@ class FillContent implements DrawingContent, KeyPathElementContent {
   }
 
   @override
-  Rect getBounds(Matrix4 parentMatrix, {bool applyParents}) {
+  Rect getBounds(Matrix4 parentMatrix, {required bool applyParents}) {
     _path.reset();
     for (var i = 0; i < _paths.length; i++) {
       _path.addPath(_paths[i].getPath(), Offset.zero,
@@ -114,7 +115,7 @@ class FillContent implements DrawingContent, KeyPathElementContent {
   }
 
   @override
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     if (property == LottieProperty.color) {
       _colorAnimation.setValueCallback(callback as LottieValueCallback<Color>);
     } else if (property == LottieProperty.opacity) {
@@ -128,8 +129,8 @@ class FillContent implements DrawingContent, KeyPathElementContent {
         _colorFilterAnimation = null;
       } else {
         _colorFilterAnimation = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<ColorFilter>);
-        _colorFilterAnimation.addUpdateListener(onValueChanged);
+            callback as LottieValueCallback<ColorFilter>, null)
+          ..addUpdateListener(onValueChanged);
         layer.addAnimation(_colorFilterAnimation);
       }
     }

lib/src/animation/content/gradient_fill_content.dart

@@ -33,9 +33,9 @@ class GradientFillContent implements DrawingContent, KeyPathElementContent {
   final BaseKeyframeAnimation<int, int> _opacityAnimation;
   final BaseKeyframeAnimation<Offset, Offset> _startPointAnimation;
   final BaseKeyframeAnimation<Offset, Offset> _endPointAnimation;
-  BaseKeyframeAnimation<ColorFilter, ColorFilter> /*?*/ _colorFilterAnimation;
-  ValueCallbackKeyframeAnimation<List<Color>,
-      List<Color>> /*?*/ _colorCallbackAnimation;
+  BaseKeyframeAnimation<ColorFilter, ColorFilter?>? _colorFilterAnimation;
+  ValueCallbackKeyframeAnimation<List<Color>, List<Color>>?
+      _colorCallbackAnimation;
   final LottieDrawable lottieDrawable;
   final int _cacheSteps;
 
@@ -62,7 +62,7 @@ class GradientFillContent implements DrawingContent, KeyPathElementContent {
   }
 
   @override
-  String get name => _fill.name;
+  String? get name => _fill.name;
 
   void invalidate() {
     lottieDrawable.invalidateSelf();
@@ -79,7 +79,8 @@ class GradientFillContent implements DrawingContent, KeyPathElementContent {
   }
 
   @override
-  void draw(Canvas canvas, Size size, Matrix4 parentMatrix, {int parentAlpha}) {
+  void draw(Canvas canvas, Size size, Matrix4 parentMatrix,
+      {required int parentAlpha}) {
     if (_fill.hidden) {
       return;
     }
@@ -99,7 +100,7 @@ class GradientFillContent implements DrawingContent, KeyPathElementContent {
     _paint.shader = gradient;
 
     if (_colorFilterAnimation != null) {
-      _paint.colorFilter = _colorFilterAnimation.value;
+      _paint.colorFilter = _colorFilterAnimation!.value;
     }
 
     var alpha =
@@ -117,7 +118,7 @@ class GradientFillContent implements DrawingContent, KeyPathElementContent {
   }
 
   @override
-  Rect getBounds(Matrix4 parentMatrix, {bool applyParents}) {
+  Rect getBounds(Matrix4 parentMatrix, {required bool applyParents}) {
     _path.reset();
     for (var i = 0; i < _paths.length; i++) {
       _path.addPath(_paths[i].getPath(), Offset.zero,
@@ -192,7 +193,7 @@ class GradientFillContent implements DrawingContent, KeyPathElementContent {
 
   List<Color> _applyDynamicColorsIfNeeded(List<Color> colors) {
     if (_colorCallbackAnimation != null) {
-      var dynamicColors = _colorCallbackAnimation.value;
+      var dynamicColors = _colorCallbackAnimation!.value;
       if (colors.length == dynamicColors.length) {
         for (var i = 0; i < colors.length; i++) {
           colors[i] = dynamicColors[i];
@@ -215,7 +216,7 @@ class GradientFillContent implements DrawingContent, KeyPathElementContent {
   }
 
   @override
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     if (property == LottieProperty.opacity) {
       _opacityAnimation.setValueCallback(callback as LottieValueCallback<int>);
     } else if (property == LottieProperty.colorFilter) {
@@ -227,8 +228,8 @@ class GradientFillContent implements DrawingContent, KeyPathElementContent {
         _colorFilterAnimation = null;
       } else {
         _colorFilterAnimation = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<ColorFilter>);
-        _colorFilterAnimation.addUpdateListener(invalidate);
+            callback as LottieValueCallback<ColorFilter>, null)
+          ..addUpdateListener(invalidate);
         layer.addAnimation(_colorFilterAnimation);
       }
     } else if (property == LottieProperty.gradientColor) {
@@ -240,8 +241,8 @@ class GradientFillContent implements DrawingContent, KeyPathElementContent {
         _colorCallbackAnimation = null;
       } else {
         _colorCallbackAnimation = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<List<Color>>);
-        _colorCallbackAnimation.addUpdateListener(invalidate);
+            callback as LottieValueCallback<List<Color>>, <Color>[])
+          ..addUpdateListener(invalidate);
         layer.addAnimation(_colorCallbackAnimation);
       }
     }

lib/src/animation/content/gradient_stroke_content.dart

@@ -18,7 +18,7 @@ class GradientStrokeContent extends BaseStrokeContent {
   static final int _cacheStepsMs = 32;
 
   @override
-  final String name;
+  final String? name;
   final bool _hidden;
   final _linearGradientCache = <int, Gradient>{};
   final _radialGradientCache = <int, Gradient>{};
@@ -28,8 +28,8 @@ class GradientStrokeContent extends BaseStrokeContent {
   final BaseKeyframeAnimation<GradientColor, GradientColor> _colorAnimation;
   final BaseKeyframeAnimation<Offset, Offset> _startPointAnimation;
   final BaseKeyframeAnimation<Offset, Offset> _endPointAnimation;
-  ValueCallbackKeyframeAnimation<List<Color>,
-      List<Color>> /*?*/ _colorCallbackAnimation;
+  ValueCallbackKeyframeAnimation<List<Color>, List<Color>>?
+      _colorCallbackAnimation;
 
   GradientStrokeContent(final LottieDrawable lottieDrawable, BaseLayer layer,
       GradientStroke stroke)
@@ -61,7 +61,8 @@ class GradientStrokeContent extends BaseStrokeContent {
   }
 
   @override
-  void draw(Canvas canvas, Size size, Matrix4 parentMatrix, {int parentAlpha}) {
+  void draw(Canvas canvas, Size size, Matrix4 parentMatrix,
+      {required int parentAlpha}) {
     if (_hidden) {
       return;
     }
@@ -142,7 +143,7 @@ class GradientStrokeContent extends BaseStrokeContent {
 
   List<Color> _applyDynamicColorsIfNeeded(List<Color> colors) {
     if (_colorCallbackAnimation != null) {
-      var dynamicColors = _colorCallbackAnimation.value;
+      var dynamicColors = _colorCallbackAnimation!.value;
       if (colors.length == dynamicColors.length) {
         for (var i = 0; i < colors.length; i++) {
           colors[i] = dynamicColors[i];
@@ -158,7 +159,7 @@ class GradientStrokeContent extends BaseStrokeContent {
   }
 
   @override
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     super.addValueCallback(property, callback);
     if (property == LottieProperty.gradientColor) {
       if (_colorCallbackAnimation != null) {
@@ -169,8 +170,8 @@ class GradientStrokeContent extends BaseStrokeContent {
         _colorCallbackAnimation = null;
       } else {
         _colorCallbackAnimation = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<List<Color>>);
-        _colorCallbackAnimation.addUpdateListener(onUpdateListener);
+            callback as LottieValueCallback<List<Color>>, <Color>[])
+          ..addUpdateListener(onUpdateListener);
         layer.addAnimation(_colorCallbackAnimation);
       }
     }

lib/src/animation/content/polystar_content.dart

@@ -28,13 +28,13 @@ class PolystarContent implements PathContent, KeyPathElementContent {
 
   final LottieDrawable lottieDrawable;
   final PolystarShape _polystarShape;
-  final BaseKeyframeAnimation<dynamic, double> _pointsAnimation;
-  final BaseKeyframeAnimation<dynamic, Offset> _positionAnimation;
-  final BaseKeyframeAnimation<dynamic, double> _rotationAnimation;
-  final BaseKeyframeAnimation<dynamic, double> /*?*/ _innerRadiusAnimation;
-  final BaseKeyframeAnimation<dynamic, double> _outerRadiusAnimation;
-  final BaseKeyframeAnimation<dynamic, double> /*?*/ _innerRoundednessAnimation;
-  final BaseKeyframeAnimation<dynamic, double> _outerRoundednessAnimation;
+  final BaseKeyframeAnimation<Object, double> _pointsAnimation;
+  final BaseKeyframeAnimation<Object, Offset> _positionAnimation;
+  final BaseKeyframeAnimation<Object, double> _rotationAnimation;
+  final BaseKeyframeAnimation<Object, double>? _innerRadiusAnimation;
+  final BaseKeyframeAnimation<Object, double> _outerRadiusAnimation;
+  final BaseKeyframeAnimation<Object, double>? _innerRoundednessAnimation;
+  final BaseKeyframeAnimation<Object, double> _outerRoundednessAnimation;
 
   final _trimPaths = CompoundTrimPathContent();
   bool _isPathValid = false;
@@ -47,11 +47,11 @@ class PolystarContent implements PathContent, KeyPathElementContent {
         _outerRoundednessAnimation =
             _polystarShape.outerRoundedness.createAnimation(),
         _innerRadiusAnimation = _polystarShape.type == PolystarShapeType.star
-            ? _polystarShape.innerRadius.createAnimation()
+            ? _polystarShape.innerRadius!.createAnimation()
             : null,
         _innerRoundednessAnimation =
             _polystarShape.type == PolystarShapeType.star
-                ? _polystarShape.innerRoundedness.createAnimation()
+                ? _polystarShape.innerRoundedness!.createAnimation()
                 : null {
     layer.addAnimation(_pointsAnimation);
     layer.addAnimation(_positionAnimation);
@@ -69,8 +69,8 @@ class PolystarContent implements PathContent, KeyPathElementContent {
     _outerRadiusAnimation.addUpdateListener(invalidate);
     _outerRoundednessAnimation.addUpdateListener(invalidate);
     if (_polystarShape.type == PolystarShapeType.star) {
-      _innerRadiusAnimation.addUpdateListener(invalidate);
-      _innerRoundednessAnimation.addUpdateListener(invalidate);
+      _innerRadiusAnimation!.addUpdateListener(invalidate);
+      _innerRoundednessAnimation!.addUpdateListener(invalidate);
     }
   }
 
@@ -123,12 +123,11 @@ class PolystarContent implements PathContent, KeyPathElementContent {
   }
 
   @override
-  String get name => _polystarShape.name;
+  String? get name => _polystarShape.name;
 
   void _createStarPath() {
     var points = _pointsAnimation.value;
-    var currentAngle =
-        _rotationAnimation == null ? 0.0 : _rotationAnimation.value;
+    var currentAngle = _rotationAnimation.value;
     // Start at +y instead of +x
     currentAngle -= 90;
     // convert to radians
@@ -143,16 +142,13 @@ class PolystarContent implements PathContent, KeyPathElementContent {
 
     var outerRadius = _outerRadiusAnimation.value;
     //noinspection ConstantConditions
-    var innerRadius = _innerRadiusAnimation.value;
+    var innerRadius = _innerRadiusAnimation!.value;
 
     var innerRoundedness = 0.0;
     if (_innerRoundednessAnimation != null) {
-      innerRoundedness = _innerRoundednessAnimation.value / 100.0;
-    }
-    var outerRoundedness = 0.0;
-    if (_outerRoundednessAnimation != null) {
-      outerRoundedness = _outerRoundednessAnimation.value / 100.0;
+      innerRoundedness = _innerRoundednessAnimation!.value / 100.0;
     }
+    var outerRoundedness = _outerRoundednessAnimation.value / 100.0;
 
     double x;
     double y;
@@ -235,8 +231,7 @@ class PolystarContent implements PathContent, KeyPathElementContent {
 
   void _createPolygonPath() {
     var points = _pointsAnimation.value.floor();
-    var currentAngle =
-        _rotationAnimation == null ? 0.0 : _rotationAnimation.value;
+    var currentAngle = _rotationAnimation.value;
     // Start at +y instead of +x
     currentAngle -= 90;
     // convert to radians
@@ -297,7 +292,7 @@ class PolystarContent implements PathContent, KeyPathElementContent {
   }
 
   @override
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     if (property == LottieProperty.polystarPoints) {
       _pointsAnimation
           .setValueCallback(callback as LottieValueCallback<double>);
@@ -309,14 +304,14 @@ class PolystarContent implements PathContent, KeyPathElementContent {
           .setValueCallback(callback as LottieValueCallback<Offset>);
     } else if (property == LottieProperty.polystarInnerRadius &&
         _innerRadiusAnimation != null) {
-      _innerRadiusAnimation
+      _innerRadiusAnimation!
           .setValueCallback(callback as LottieValueCallback<double>);
     } else if (property == LottieProperty.polystarOuterRadius) {
       _outerRadiusAnimation
           .setValueCallback(callback as LottieValueCallback<double>);
     } else if (property == LottieProperty.polystarInnerRoundedness &&
         _innerRoundednessAnimation != null) {
-      _innerRoundednessAnimation
+      _innerRoundednessAnimation!
           .setValueCallback(callback as LottieValueCallback<double>);
     } else if (property == LottieProperty.polystarOuterRoundedness) {
       _outerRoundednessAnimation

lib/src/animation/content/rectangle_content.dart

@@ -21,12 +21,12 @@ class RectangleContent implements KeyPathElementContent, PathContent {
   final _path = PathFactory.create();
 
   @override
-  final String name;
+  final String? name;
   final bool _hidden;
   final LottieDrawable lottieDrawable;
-  final BaseKeyframeAnimation<dynamic, Offset> _positionAnimation;
-  final BaseKeyframeAnimation<dynamic, Offset> _sizeAnimation;
-  final BaseKeyframeAnimation<dynamic, double> _cornerRadiusAnimation;
+  final BaseKeyframeAnimation<Object, Offset> _positionAnimation;
+  final BaseKeyframeAnimation<Object, Offset> _sizeAnimation;
+  final BaseKeyframeAnimation<Object, double> _cornerRadiusAnimation;
 
   final CompoundTrimPathContent _trimPaths = CompoundTrimPathContent();
   bool _isPathValid = false;
@@ -81,8 +81,7 @@ class RectangleContent implements KeyPathElementContent, PathContent {
     var size = _sizeAnimation.value;
     var halfWidth = size.dx / 2.0;
     var halfHeight = size.dy / 2.0;
-    var radius =
-        _cornerRadiusAnimation == null ? 0.0 : _cornerRadiusAnimation.value;
+    var radius = _cornerRadiusAnimation.value;
     var maxRadius = min(halfWidth, halfHeight);
     if (radius > maxRadius) {
       radius = maxRadius;
@@ -164,7 +163,7 @@ class RectangleContent implements KeyPathElementContent, PathContent {
   }
 
   @override
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     if (property == LottieProperty.rectangleSize) {
       _sizeAnimation.setValueCallback(callback as LottieValueCallback<Offset>);
     } else if (property == LottieProperty.position) {

lib/src/animation/content/repeater_content.dart

@@ -33,7 +33,7 @@ class RepeaterContent
   final BaseKeyframeAnimation<double, double> _copies;
   final BaseKeyframeAnimation<double, double> _offset;
   final TransformKeyframeAnimation _transform;
-  ContentGroup _contentGroup;
+  ContentGroup? _contentGroup;
 
   RepeaterContent(this.lottieDrawable, this.layer, this._repeater)
       : _copies = _repeater.copies.createAnimation(),
@@ -83,16 +83,16 @@ class RepeaterContent
   }
 
   @override
-  String get name => _repeater.name;
+  String? get name => _repeater.name;
 
   @override
   void setContents(List<Content> contentsBefore, List<Content> contentsAfter) {
-    _contentGroup.setContents(contentsBefore, contentsAfter);
+    _contentGroup!.setContents(contentsBefore, contentsAfter);
   }
 
   @override
   Path getPath() {
-    var contentPath = _contentGroup.getPath();
+    var contentPath = _contentGroup!.getPath();
     _path.reset();
     var copies = _copies.value;
     var offset = _offset.value;
@@ -104,23 +104,24 @@ class RepeaterContent
   }
 
   @override
-  void draw(Canvas canvas, Size size, Matrix4 parentMatrix, {int parentAlpha}) {
+  void draw(Canvas canvas, Size size, Matrix4 parentMatrix,
+      {required int parentAlpha}) {
     var copies = _copies.value;
     var offset = _offset.value;
-    var startOpacity = _transform.startOpacity.value / 100.0;
-    var endOpacity = _transform.endOpacity.value / 100.0;
+    var startOpacity = _transform.startOpacity!.value / 100.0;
+    var endOpacity = _transform.endOpacity!.value / 100.0;
     for (var i = copies.toInt() - 1; i >= 0; i--) {
       _matrix.set(parentMatrix);
       _matrix.preConcat(_transform.getMatrixForRepeater(i + offset));
       var newAlpha =
-          parentAlpha * lerpDouble(startOpacity, endOpacity, i / copies);
-      _contentGroup.draw(canvas, size, _matrix, parentAlpha: newAlpha.round());
+          parentAlpha * lerpDouble(startOpacity, endOpacity, i / copies)!;
+      _contentGroup!.draw(canvas, size, _matrix, parentAlpha: newAlpha.round());
     }
   }
 
   @override
-  Rect getBounds(Matrix4 parentMatrix, {bool applyParents}) {
-    return _contentGroup.getBounds(parentMatrix, applyParents: applyParents);
+  Rect getBounds(Matrix4 parentMatrix, {required bool applyParents}) {
+    return _contentGroup!.getBounds(parentMatrix, applyParents: applyParents);
   }
 
   void _invalidate() {
@@ -135,7 +136,7 @@ class RepeaterContent
   }
 
   @override
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     if (_transform.applyValueCallback(property, callback)) {
       return;
     }

lib/src/animation/content/shape_content.dart

@@ -17,7 +17,7 @@ class ShapeContent implements PathContent {
   final ShapePath _shape;
 
   final LottieDrawable lottieDrawable;
-  final BaseKeyframeAnimation<dynamic, Path> _shapeAnimation;
+  final BaseKeyframeAnimation<Object, Path> _shapeAnimation;
 
   bool _isPathValid = false;
   final _trimPaths = CompoundTrimPathContent();
@@ -48,7 +48,7 @@ class ShapeContent implements PathContent {
   }
 
   @override
-  String get name => _shape.name;
+  String? get name => _shape.name;
 
   @override
   Path getPath() {

lib/src/animation/content/stroke_content.dart

@@ -11,10 +11,10 @@ import 'base_stroke_content.dart';
 
 class StrokeContent extends BaseStrokeContent {
   @override
-  final String name;
+  final String? name;
   final bool _hidden;
   final BaseKeyframeAnimation<Color, Color> _colorAnimation;
-  BaseKeyframeAnimation<ColorFilter, ColorFilter> /*?*/ _colorFilterAnimation;
+  BaseKeyframeAnimation<ColorFilter, ColorFilter?>? _colorFilterAnimation;
 
   StrokeContent(
       final LottieDrawable lottieDrawable, BaseLayer layer, ShapeStroke stroke)
@@ -34,19 +34,20 @@ class StrokeContent extends BaseStrokeContent {
   }
 
   @override
-  void draw(Canvas canvas, Size size, Matrix4 parentMatrix, {int parentAlpha}) {
+  void draw(Canvas canvas, Size size, Matrix4 parentMatrix,
+      {required int parentAlpha}) {
     if (_hidden) {
       return;
     }
     paint.color = _colorAnimation.value.withAlpha(paint.color.alpha);
     if (_colorFilterAnimation != null) {
-      paint.colorFilter = _colorFilterAnimation.value;
+      paint.colorFilter = _colorFilterAnimation!.value;
     }
     super.draw(canvas, size, parentMatrix, parentAlpha: parentAlpha);
   }
 
   @override
-  void addValueCallback<T>(T property, LottieValueCallback<T> /*?*/ callback) {
+  void addValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     super.addValueCallback(property, callback);
     if (property == LottieProperty.strokeColor) {
       _colorAnimation.setValueCallback(callback as LottieValueCallback<Color>);
@@ -58,10 +59,9 @@ class StrokeContent extends BaseStrokeContent {
       if (callback == null) {
         _colorFilterAnimation = null;
       } else {
-        _colorFilterAnimation =
-            ValueCallbackKeyframeAnimation<ColorFilter, ColorFilter>(
-                callback as LottieValueCallback<ColorFilter>);
-        _colorFilterAnimation.addUpdateListener(onUpdateListener);
+        _colorFilterAnimation = ValueCallbackKeyframeAnimation(
+            callback as LottieValueCallback<ColorFilter>, null)
+          ..addUpdateListener(onUpdateListener);
         layer.addAnimation(_colorAnimation);
       }
     }

lib/src/animation/content/trim_path_content.dart

@@ -5,13 +5,13 @@ import 'content.dart';
 
 class TrimPathContent implements Content {
   @override
-  final String name;
+  final String? name;
   final bool hidden;
   final _listeners = <void Function()>[];
-  final ShapeTrimPathType type;
-  final BaseKeyframeAnimation<dynamic, double> start;
-  final BaseKeyframeAnimation<dynamic, double> end;
-  final BaseKeyframeAnimation<dynamic, double> offset;
+  final ShapeTrimPathType? type;
+  final BaseKeyframeAnimation<Object, double> start;
+  final BaseKeyframeAnimation<Object, double> end;
+  final BaseKeyframeAnimation<Object, double> offset;
 
   TrimPathContent(BaseLayer layer, ShapeTrimPath trimPath)
       : name = trimPath.name,

lib/src/animation/keyframe/base_keyframe_animation.dart

@@ -5,16 +5,16 @@ import '../../value/lottie_value_callback.dart';
 
 /// @param <K> Keyframe type
 /// @param <A> Animation type
-abstract class BaseKeyframeAnimation<K, A> {
+abstract class BaseKeyframeAnimation<K extends Object, A extends Object?> {
 // This is not a Set because we don't want to create an iterator object on every setProgress.
   final listeners = <void Function()>[];
   bool _isDiscrete = false;
 
   final _KeyframesWrapper<K> _keyframesWrapper;
   double _progress = 0;
-  LottieValueCallback<A> /*?*/ valueCallback;
+  LottieValueCallback<A>? valueCallback;
 
-  A /*?*/ _cachedGetValue;
+  A? _cachedGetValue;
 
   double _cachedStartDelayProgress = -1.0;
   double _cachedEndProgress = -1.0;
@@ -85,7 +85,7 @@ abstract class BaseKeyframeAnimation<K, A> {
     if (keyframe.isStatic) {
       return 0.0;
     }
-    return keyframe.interpolator.transform(getLinearCurrentKeyframeProgress());
+    return keyframe.interpolator!.transform(getLinearCurrentKeyframeProgress());
   }
 
   double getStartDelayProgress() {
@@ -106,7 +106,7 @@ abstract class BaseKeyframeAnimation<K, A> {
     var progress = getInterpolatedCurrentKeyframeProgress();
     if (valueCallback == null &&
         _keyframesWrapper.isCachedValueEnabled(progress)) {
-      return _cachedGetValue;
+      return _cachedGetValue!;
     }
 
     final keyframe = getCurrentKeyframe();
@@ -125,9 +125,9 @@ abstract class BaseKeyframeAnimation<K, A> {
     _progress = value;
   }
 
-  void setValueCallback(LottieValueCallback<A> /*?*/ valueCallback) {
+  void setValueCallback(LottieValueCallback<A>? valueCallback) {
     if (this.valueCallback != null) {
-      this.valueCallback.setAnimation(null);
+      this.valueCallback!.setAnimation(null);
     }
     this.valueCallback = valueCallback;
     if (valueCallback != null) {
@@ -240,8 +240,8 @@ class _SingleKeyframeWrapper<T> implements _KeyframesWrapper<T> {
 
 class _KeyframesWrapperImpl<T> implements _KeyframesWrapper<T> {
   final List<Keyframe<T>> keyframes;
-  Keyframe<T> _currentKeyframe;
-  Keyframe<T> _cachedCurrentKeyframe;
+  Keyframe<T>? _currentKeyframe;
+  Keyframe<T>? _cachedCurrentKeyframe;
   double _cachedInterpolatedProgress = -1;
 
   _KeyframesWrapperImpl(this.keyframes) {
@@ -255,8 +255,8 @@ class _KeyframesWrapperImpl<T> implements _KeyframesWrapper<T> {
 
   @override
   bool isValueChanged(double progress) {
-    if (_currentKeyframe.containsProgress(progress)) {
-      return !_currentKeyframe.isStatic;
+    if (_currentKeyframe!.containsProgress(progress)) {
+      return !_currentKeyframe!.isStatic;
     }
     _currentKeyframe = findKeyframe(progress);
     return true;
@@ -281,7 +281,7 @@ class _KeyframesWrapperImpl<T> implements _KeyframesWrapper<T> {
 
   @override
   Keyframe<T> getCurrentKeyframe() {
-    return _currentKeyframe;
+    return _currentKeyframe!;
   }
 
   @override

lib/src/animation/keyframe/color_keyframe_animation.dart

@@ -15,7 +15,7 @@ class ColorKeyframeAnimation extends KeyframeAnimation<Color> {
     var endColor = keyframe.endValue;
 
     if (valueCallback != null) {
-      var value = valueCallback.getValueInternal(
+      var value = valueCallback!.getValueInternal(
           keyframe.startFrame,
           keyframe.endFrame,
           startColor,
@@ -29,6 +29,6 @@ class ColorKeyframeAnimation extends KeyframeAnimation<Color> {
     }
 
     return GammaEvaluator.evaluate(
-        keyframeProgress.clamp(0, 1).toDouble(), startColor, endColor);
+        keyframeProgress.clamp(0, 1).toDouble(), startColor!, endColor!);
   }
 }

lib/src/animation/keyframe/double_keyframe_animation.dart

@@ -12,7 +12,7 @@ class DoubleKeyframeAnimation extends KeyframeAnimation<double> {
     }
 
     if (valueCallback != null) {
-      var value = valueCallback.getValueInternal(
+      var value = valueCallback!.getValueInternal(
           keyframe.startFrame,
           keyframe.endFrame,
           keyframe.startValue,
@@ -25,6 +25,7 @@ class DoubleKeyframeAnimation extends KeyframeAnimation<double> {
       }
     }
 
-    return lerpDouble(keyframe.startValue, keyframe.endValue, keyframeProgress);
+    return lerpDouble(
+        keyframe.startValue, keyframe.endValue, keyframeProgress)!;
   }
 }

lib/src/animation/keyframe/gradient_color_keyframe_animation.dart

@@ -4,7 +4,7 @@ import '../../value/keyframe.dart';
 import 'keyframe_animation.dart';
 
 class GradientColorKeyframeAnimation extends KeyframeAnimation<GradientColor> {
-  GradientColor _gradientColor;
+  late GradientColor _gradientColor;
 
   GradientColorKeyframeAnimation(List<Keyframe<GradientColor>> keyframes)
       : super(keyframes) {
@@ -18,7 +18,7 @@ class GradientColorKeyframeAnimation extends KeyframeAnimation<GradientColor> {
   GradientColor getValue(
       Keyframe<GradientColor> keyframe, double keyframeProgress) {
     _gradientColor.lerp(
-        keyframe.startValue, keyframe.endValue, keyframeProgress);
+        keyframe.startValue!, keyframe.endValue!, keyframeProgress);
     return _gradientColor;
   }
 }

lib/src/animation/keyframe/integer_keyframe_animation.dart

@@ -12,7 +12,7 @@ class IntegerKeyframeAnimation extends KeyframeAnimation<int> {
     }
 
     if (valueCallback != null) {
-      var value = valueCallback.getValueInternal(
+      var value = valueCallback!.getValueInternal(
           keyframe.startFrame,
           keyframe.endFrame,
           keyframe.startValue,
@@ -25,7 +25,7 @@ class IntegerKeyframeAnimation extends KeyframeAnimation<int> {
       }
     }
 
-    return lerpDouble(keyframe.startValue, keyframe.endValue, keyframeProgress)
+    return lerpDouble(keyframe.startValue, keyframe.endValue, keyframeProgress)!
         .round();
   }
 }

lib/src/animation/keyframe/keyframe_animation.dart

@@ -1,6 +1,7 @@
 import '../../value/keyframe.dart';
 import 'base_keyframe_animation.dart';
 
-abstract class KeyframeAnimation<T> extends BaseKeyframeAnimation<T, T> {
+abstract class KeyframeAnimation<T extends Object>
+    extends BaseKeyframeAnimation<T, T> {
   KeyframeAnimation(List<Keyframe<T>> keyframes) : super(keyframes);
 }

lib/src/animation/keyframe/path_keyframe.dart

@@ -4,7 +4,7 @@ import '../../utils/utils.dart';
 import '../../value/keyframe.dart';
 
 class PathKeyframe extends Keyframe<Offset> {
-  Path _path;
+  Path? _path;
   final Keyframe<Offset> _pointKeyFrame;
 
   PathKeyframe(LottieComposition composition, Keyframe<Offset> keyframe)
@@ -22,13 +22,13 @@ class PathKeyframe extends Keyframe<Offset> {
     var equals =
         endValue != null && startValue != null && startValue == endValue;
     if (endValue != null && !equals) {
-      _path = Utils.createPath(
-          startValue, endValue, _pointKeyFrame.pathCp1, _pointKeyFrame.pathCp2);
+      _path = Utils.createPath(startValue!, endValue!, _pointKeyFrame.pathCp1,
+          _pointKeyFrame.pathCp2);
     }
   }
 
   /// This will be null if the startValue and endValue are the same. */
-  Path /*?*/ getPath() {
+  Path? getPath() {
     return _path;
   }
 }

lib/src/animation/keyframe/path_keyframe_animation.dart

@@ -4,8 +4,8 @@ import 'keyframe_animation.dart';
 import 'path_keyframe.dart';
 
 class PathKeyframeAnimation extends KeyframeAnimation<Offset> {
-  PathKeyframe _pathMeasureKeyframe;
-  PathMetric _pathMeasure;
+  PathKeyframe? _pathMeasureKeyframe;
+  late PathMetric _pathMeasure;
 
   PathKeyframeAnimation(List<Keyframe<Offset>> keyframes) : super(keyframes);
 
@@ -14,11 +14,11 @@ class PathKeyframeAnimation extends KeyframeAnimation<Offset> {
     var pathKeyframe = keyframe as PathKeyframe;
     var path = pathKeyframe.getPath();
     if (path == null) {
-      return keyframe.startValue;
+      return keyframe.startValue!;
     }
 
     if (valueCallback != null) {
-      var value = valueCallback.getValueInternal(
+      var value = valueCallback!.getValueInternal(
           pathKeyframe.startFrame,
           pathKeyframe.endFrame,
           pathKeyframe.startValue,
@@ -37,7 +37,7 @@ class PathKeyframeAnimation extends KeyframeAnimation<Offset> {
     }
 
     return _pathMeasure
-        .getTangentForOffset(keyframeProgress * _pathMeasure.length)
+        .getTangentForOffset(keyframeProgress * _pathMeasure.length)!
         .position;
   }
 }

lib/src/animation/keyframe/point_keyframe_animation.dart

@@ -15,7 +15,7 @@ class PointKeyframeAnimation extends KeyframeAnimation<Offset> {
     var endPoint = keyframe.endValue;
 
     if (valueCallback != null) {
-      var value = valueCallback.getValueInternal(
+      var value = valueCallback!.getValueInternal(
           keyframe.startFrame,
           keyframe.endFrame,
           startPoint,
@@ -28,6 +28,6 @@ class PointKeyframeAnimation extends KeyframeAnimation<Offset> {
       }
     }
 
-    return Offset.lerp(startPoint, endPoint, keyframeProgress);
+    return Offset.lerp(startPoint, endPoint, keyframeProgress)!;
   }
 }

lib/src/animation/keyframe/shape_keyframe_animation.dart

@@ -14,8 +14,8 @@ class ShapeKeyframeAnimation extends BaseKeyframeAnimation<ShapeData, Path> {
 
   @override
   Path getValue(Keyframe<ShapeData> keyframe, double keyframeProgress) {
-    var startShapeData = keyframe.startValue;
-    var endShapeData = keyframe.endValue;
+    var startShapeData = keyframe.startValue!;
+    var endShapeData = keyframe.endValue!;
 
     _tempShapeData.interpolateBetween(
         startShapeData, endShapeData, keyframeProgress);

lib/src/animation/keyframe/split_dimension_path_keyframe_animation.dart

@@ -4,7 +4,7 @@ import 'base_keyframe_animation.dart';
 
 class SplitDimensionPathKeyframeAnimation
     extends BaseKeyframeAnimation<Offset, Offset> {
-  Offset _point;
+  late Offset _point;
   final BaseKeyframeAnimation<double, double> _xAnimation;
   final BaseKeyframeAnimation<double, double> _yAnimation;
 
@@ -26,7 +26,7 @@ class SplitDimensionPathKeyframeAnimation
 
   @override
   Offset get value {
-    return getValue(null, 0);
+    return _point;
   }
 
   @override

lib/src/animation/keyframe/text_keyframe_animation.dart

@@ -9,6 +9,6 @@ class TextKeyframeAnimation extends KeyframeAnimation<DocumentData> {
   @override
   DocumentData getValue(
       Keyframe<DocumentData> keyframe, double keyframeProgress) {
-    return keyframe.startValue;
+    return keyframe.startValue!;
   }
 }

lib/src/animation/keyframe/transform_keyframe_animation.dart

@@ -30,25 +30,25 @@ class TransformKeyframeAnimation {
         _endOpacity = animatableTransform.endOpacity?.createAnimation();
 
   final _matrix = Matrix4.identity();
-  final Matrix4 _skewMatrix1;
-  final Matrix4 _skewMatrix2;
-  final Matrix4 _skewMatrix3;
+  final Matrix4? _skewMatrix1;
+  final Matrix4? _skewMatrix2;
+  final Matrix4? _skewMatrix3;
 
-  BaseKeyframeAnimation<Offset, Offset> /*?*/ _anchorPoint;
-  BaseKeyframeAnimation<Offset, Offset> /*?*/ _position;
-  BaseKeyframeAnimation<Offset, Offset> /*?*/ _scale;
-  BaseKeyframeAnimation<double, double> /*?*/ _rotation;
-  DoubleKeyframeAnimation /*?*/ _skew;
-  DoubleKeyframeAnimation /*?*/ _skewAngle;
+  BaseKeyframeAnimation<Offset, Offset>? _anchorPoint;
+  BaseKeyframeAnimation<Offset, Offset>? _position;
+  BaseKeyframeAnimation<Offset, Offset>? _scale;
+  BaseKeyframeAnimation<double, double>? _rotation;
+  DoubleKeyframeAnimation? _skew;
+  DoubleKeyframeAnimation? _skewAngle;
 
-  BaseKeyframeAnimation<int, int> /*?*/ _opacity;
-  BaseKeyframeAnimation<int, int> /*?*/ get opacity => _opacity;
+  BaseKeyframeAnimation<int, int>? _opacity;
+  BaseKeyframeAnimation<int, int>? get opacity => _opacity;
 
-  BaseKeyframeAnimation<double, double> /*?*/ _startOpacity;
-  BaseKeyframeAnimation<double, double> /*?*/ get startOpacity => _startOpacity;
+  BaseKeyframeAnimation<double, double>? _startOpacity;
+  BaseKeyframeAnimation<double, double>? get startOpacity => _startOpacity;
 
-  BaseKeyframeAnimation<double, double> /*?*/ _endOpacity;
-  BaseKeyframeAnimation<double, double> /*?*/ get endOpacity => _endOpacity;
+  BaseKeyframeAnimation<double, double>? _endOpacity;
+  BaseKeyframeAnimation<double, double>? get endOpacity => _endOpacity;
 
   void addAnimationsToLayer(BaseLayer layer) {
     layer.addAnimation(_opacity);
@@ -91,14 +91,14 @@ class TransformKeyframeAnimation {
     _matrix.reset();
 
     if (_position != null) {
-      final position = _position.value;
+      final position = _position!.value;
       if (position.dx != 0 || position.dy != 0) {
         _matrix.translate(position.dx, position.dy);
       }
     }
 
     if (_rotation != null) {
-      final rotation = _rotation.value;
+      final rotation = _rotation!.value;
       if (rotation != 0) {
         _matrix.rotateZ(rotation * pi / 180.0);
       }
@@ -106,46 +106,46 @@ class TransformKeyframeAnimation {
 
     if (_skew != null) {
       final mCos =
-          _skewAngle == null ? 0.0 : cos(radians(-_skewAngle.value + 90));
+          _skewAngle == null ? 0.0 : cos(radians(-_skewAngle!.value + 90));
       final mSin =
-          _skewAngle == null ? 1.0 : sin(radians(-_skewAngle.value + 90));
-      final aTan = tan(radians(_skew.value));
+          _skewAngle == null ? 1.0 : sin(radians(-_skewAngle!.value + 90));
+      final aTan = tan(radians(_skew!.value));
 
-      _skewMatrix1.setValues(
+      _skewMatrix1!.setValues(
         mCos, mSin, 0, 0,
         -mSin, mCos, 0, 0,
         0, 0, 1, 0,
         0, 0, 0, 1, //
       );
 
-      _skewMatrix2.setValues(
+      _skewMatrix2!.setValues(
         1, 0, 0, 0,
         aTan, 1, 0, 0,
         0, 0, 1, 0,
         0, 0, 0, 1, //
       );
 
-      _skewMatrix3.setValues(
+      _skewMatrix3!.setValues(
         mCos, -mSin, 0, 0,
         mSin, mCos, 0, 0,
         0, 0, 1, 0,
         0, 0, 0, 1, //
       );
 
-      _skewMatrix2.multiply(_skewMatrix1);
-      _skewMatrix3.multiply(_skewMatrix2);
-      _matrix.multiply(_skewMatrix3);
+      _skewMatrix2!.multiply(_skewMatrix1!);
+      _skewMatrix3!.multiply(_skewMatrix2!);
+      _matrix.multiply(_skewMatrix3!);
     }
 
     if (_scale != null) {
-      final scale = _scale.value;
+      final scale = _scale!.value;
       if (scale.dx != 1 || scale.dy != 1) {
         _matrix.scale(scale.dx, scale.dy);
       }
     }
 
     if (_anchorPoint != null) {
-      final anchorPoint = _anchorPoint.value;
+      final anchorPoint = _anchorPoint!.value;
       if (anchorPoint.dx != 0 || anchorPoint.dy != 0) {
         _matrix.translate(-anchorPoint.dx, -anchorPoint.dy);
       }
@@ -171,7 +171,7 @@ class TransformKeyframeAnimation {
     }
 
     if (_rotation != null) {
-      var rotation = _rotation.value;
+      var rotation = _rotation!.value;
       var anchorPoint = _anchorPoint?.value;
       _matrix.rotate(
           Vector3(anchorPoint == null ? 0.0 : anchorPoint.dx,
@@ -182,62 +182,64 @@ class TransformKeyframeAnimation {
     return _matrix;
   }
 
-  bool applyValueCallback<T>(T property, LottieValueCallback<T> callback) {
+  bool applyValueCallback<T>(T property, LottieValueCallback<T>? callback) {
     if (property == LottieProperty.transformAnchorPoint) {
       if (_anchorPoint == null) {
         _anchorPoint = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<Offset>, Offset.zero);
+            callback as LottieValueCallback<Offset>?, Offset.zero);
       } else {
-        _anchorPoint.setValueCallback(callback as LottieValueCallback<Offset>);
+        _anchorPoint!
+            .setValueCallback(callback as LottieValueCallback<Offset>?);
       }
     } else if (property == LottieProperty.transformPosition) {
       if (_position == null) {
         _position = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<Offset>, Offset.zero);
+            callback as LottieValueCallback<Offset>?, Offset.zero);
       } else {
-        _position.setValueCallback(callback as LottieValueCallback<Offset>);
+        _position!.setValueCallback(callback as LottieValueCallback<Offset>?);
       }
     } else if (property == LottieProperty.transformScale) {
       if (_scale == null) {
         _scale = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<Offset>, Offset(1, 1));
+            callback as LottieValueCallback<Offset>?, Offset(1, 1));
       } else {
-        _scale.setValueCallback(callback as LottieValueCallback<Offset>);
+        _scale!.setValueCallback(callback as LottieValueCallback<Offset>?);
       }
     } else if (property == LottieProperty.transformRotation) {
       if (_rotation == null) {
         _rotation = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<double>, 0.0);
+            callback as LottieValueCallback<double>?, 0.0);
       } else {
-        _rotation.setValueCallback(callback as LottieValueCallback<double>);
+        _rotation!.setValueCallback(callback as LottieValueCallback<double>?);
       }
     } else if (property == LottieProperty.transformOpacity) {
       if (_opacity == null) {
         _opacity = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<int>, 100);
+            callback as LottieValueCallback<int>?, 100);
       } else {
-        _opacity.setValueCallback(callback as LottieValueCallback<int>);
+        _opacity!.setValueCallback(callback as LottieValueCallback<int>?);
       }
     } else if (property == LottieProperty.transformStartOpacity) {
       if (_startOpacity == null) {
         _startOpacity = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<double>, 100);
+            callback as LottieValueCallback<double>?, 100);
       } else {
-        _startOpacity.setValueCallback(callback as LottieValueCallback<double>);
+        _startOpacity!
+            .setValueCallback(callback as LottieValueCallback<double>?);
       }
     } else if (property == LottieProperty.transformEndOpacity) {
       if (_endOpacity == null) {
         _endOpacity = ValueCallbackKeyframeAnimation(
-            callback as LottieValueCallback<double>, 100);
+            callback as LottieValueCallback<double>?, 100);
       } else {
-        _endOpacity.setValueCallback(callback as LottieValueCallback<double>);
+        _endOpacity!.setValueCallback(callback as LottieValueCallback<double>?);
       }
     } else if (property == LottieProperty.transformSkew) {
       _skew ??= DoubleKeyframeAnimation([Keyframe.nonAnimated(0.0)]);
-      _skew.setValueCallback(callback as LottieValueCallback<double>);
+      _skew!.setValueCallback(callback as LottieValueCallback<double>?);
     } else if (property == LottieProperty.transformSkewAngle) {
       _skewAngle ??= DoubleKeyframeAnimation([Keyframe.nonAnimated(0.0)]);
-      _skewAngle.setValueCallback(callback as LottieValueCallback<double>);
+      _skewAngle!.setValueCallback(callback as LottieValueCallback<double>?);
     } else {
       return false;
     }

lib/src/animation/keyframe/value_callback_keyframe_animation.dart

@@ -2,11 +2,12 @@ import '../../value/keyframe.dart';
 import '../../value/lottie_value_callback.dart';
 import 'base_keyframe_animation.dart';
 
-class ValueCallbackKeyframeAnimation<K, A> extends BaseKeyframeAnimation<K, A> {
+class ValueCallbackKeyframeAnimation<K extends Object, A extends Object?>
+    extends BaseKeyframeAnimation<K, A> {
   final A valueCallbackValue;
 
-  ValueCallbackKeyframeAnimation(LottieValueCallback<A> valueCallback,
-      [A /*?*/ valueCallbackValue])
+  ValueCallbackKeyframeAnimation(
+      LottieValueCallback<A>? valueCallback, A valueCallbackValue)
       : valueCallbackValue = valueCallbackValue,
         super([]) {
     setValueCallback(valueCallback);
@@ -33,7 +34,7 @@ class ValueCallbackKeyframeAnimation<K, A> extends BaseKeyframeAnimation<K, A> {
 
   @override
   A get value {
-    return valueCallback.getValueInternal(0.0, 0.0, valueCallbackValue,
+    return valueCallback!.getValueInternal(0.0, 0.0, valueCallbackValue,
             valueCallbackValue, progress, progress, progress) ??
         valueCallbackValue;
   }

lib/src/composition.dart

@@ -1,6 +1,7 @@
 import 'dart:math';
 import 'dart:typed_data';
 import 'package:archive/archive.dart';
+import 'package:collection/collection.dart' show IterableExtension;
 import 'package:flutter/widgets.dart';
 import 'package:path/path.dart' as p;
 import 'frame_rate.dart';
@@ -15,43 +16,31 @@ import 'parser/moshi/json_reader.dart';
 import 'performance_tracker.dart';
 import 'providers/load_image.dart';
 
-void internalInit(
-    LottieComposition composition,
-    Rectangle<int> bounds,
-    double startFrame,
-    double endFrame,
-    double frameRate,
-    List<Layer> layers,
-    Map<int, Layer> layerMap,
-    Map<String, List<Layer>> precomps,
-    Map<String, LottieImageAsset> images,
-    Map<int, FontCharacter> characters,
-    Map<String, Font> fonts,
-    List<Marker> markers) {
-  assert(startFrame != endFrame, 'startFrame == endFrame ($startFrame)');
-  assert(frameRate > 0, 'invalid framerate: $frameRate');
-  composition
-    .._bounds = bounds
-    .._startFrame = startFrame
-    .._endFrame = endFrame
-    .._frameRate = frameRate
-    .._layers = layers
-    .._layerMap = layerMap
-    .._precomps = precomps
-    .._images = images
-    .._characters = characters
-    .._fonts = fonts
-    .._markers = markers;
+class CompositionParameters {
+  MutableRectangle<int> bounds = MutableRectangle<int>(0, 0, 0, 0);
+  double startFrame = 0.0;
+  double endFrame = 0;
+  double frameRate = 0;
+  final layers = <Layer>[];
+  final layerMap = <int, Layer>{};
+  final precomps = <String, List<Layer>>{};
+  final images = <String, LottieImageAsset>{};
+  final characters = <int, FontCharacter>{};
+  final fonts = <String, Font>{};
+  final markers = <Marker>[];
+
+  static CompositionParameters forComposition(LottieComposition composition) =>
+      composition._parameters;
 }
 
 class LottieComposition {
-  static Future<LottieComposition> fromByteData(ByteData data, {String name}) {
+  static Future<LottieComposition> fromByteData(ByteData data, {String? name}) {
     return fromBytes(data.buffer.asUint8List(), name: name);
   }
 
   static Future<LottieComposition> fromBytes(Uint8List bytes,
-      {String name}) async {
-    Archive archive;
+      {String? name}) async {
+    Archive? archive;
     if (bytes[0] == 0x50 && bytes[1] == 0x4B) {
       archive = ZipDecoder().decodeBytes(bytes);
       var jsonFile = archive.files.firstWhere((e) => e.name.endsWith('.json'));
@@ -64,9 +53,8 @@ class LottieComposition {
     if (archive != null) {
       for (var image in composition.images.values) {
         var imagePath = p.posix.join(image.dirName, image.fileName);
-        var found = archive.files.firstWhere(
-            (f) => f.name.toLowerCase() == imagePath.toLowerCase(),
-            orElse: () => null);
+        var found = archive.files.firstWhereOrNull(
+            (f) => f.name.toLowerCase() == imagePath.toLowerCase());
         if (found != null) {
           image.loadedImage = await loadImage(
               composition, image, MemoryImage(found.content as Uint8List));
@@ -79,23 +67,13 @@ class LottieComposition {
 
   LottieComposition._(this.name);
 
-  final String name;
+  final String? name;
   final _performanceTracker = PerformanceTracker();
   // This is stored as a set to avoid duplicates.
   final _warnings = <String>{};
-  Map<String, List<Layer>> _precomps;
-  Map<String, LottieImageAsset> _images;
 
   /// Map of font names to fonts */
-  Map<String, Font> _fonts;
-  List<Marker> _markers;
-  Map<int, FontCharacter> _characters;
-  Map<int, Layer> _layerMap;
-  List<Layer> _layers;
-  Rectangle<int> _bounds;
-  double _startFrame;
-  double _endFrame;
-  double _frameRate;
+  final _parameters = CompositionParameters();
 
   /// Used to determine if an animation can be drawn with hardware acceleration.
   bool hasDashPattern = false;
@@ -106,7 +84,7 @@ class LottieComposition {
   int _maskAndMatteCount = 0;
 
   void addWarning(String warning) {
-    var prefix = name != null && name.isNotEmpty ? '$name: ' : '';
+    var prefix = name != null && name!.isNotEmpty ? '$name: ' : '';
     logger.warning('$prefix$warning');
     _warnings.add(warning);
   }
@@ -127,39 +105,39 @@ class LottieComposition {
 
   PerformanceTracker get performanceTracker => _performanceTracker;
 
-  Layer layerModelForId(int id) {
-    return _layerMap[id];
+  Layer? layerModelForId(int id) {
+    return _parameters.layerMap[id];
   }
 
-  Rectangle<int> get bounds => _bounds;
+  Rectangle<int> get bounds => _parameters.bounds;
 
   Duration get duration {
     return Duration(milliseconds: (seconds * 1000).round());
   }
 
-  double get seconds => durationFrames / _frameRate;
+  double get seconds => durationFrames / frameRate;
 
-  double get startFrame => _startFrame;
+  double get startFrame => _parameters.startFrame;
 
-  double get endFrame => _endFrame;
+  double get endFrame => _parameters.endFrame;
 
-  double get frameRate => _frameRate;
+  double get frameRate => _parameters.frameRate;
 
-  List<Layer> get layers => _layers;
+  List<Layer> get layers => _parameters.layers;
 
-  List<Layer> /*?*/ getPrecomps(String id) {
-    return _precomps[id];
+  List<Layer>? getPrecomps(String? id) {
+    return _parameters.precomps[id];
   }
 
-  Map<int, FontCharacter> get characters => _characters;
+  Map<int, FontCharacter> get characters => _parameters.characters;
 
-  Map<String, Font> get fonts => _fonts;
+  Map<String, Font> get fonts => _parameters.fonts;
 
-  List<Marker> get markers => _markers;
+  List<Marker> get markers => _parameters.markers;
 
-  Marker /*?*/ getMarker(String markerName) {
-    for (var i = 0; i < _markers.length; i++) {
-      var marker = _markers[i];
+  Marker? getMarker(String markerName) {
+    for (var i = 0; i < markers.length; i++) {
+      var marker = markers[i];
       if (marker.matchesName(markerName)) {
         return marker;
       }
@@ -168,20 +146,20 @@ class LottieComposition {
   }
 
   bool get hasImages {
-    return _images.isNotEmpty;
+    return images.isNotEmpty;
   }
 
   Map<String, LottieImageAsset> get images {
-    return _images;
+    return _parameters.images;
   }
 
   double get durationFrames {
-    return _endFrame - _startFrame;
+    return endFrame - startFrame;
   }
 
   /// Returns a "rounded" progress value according to the frameRate
-  double roundProgress(double progress, {@required FrameRate frameRate}) {
-    num fps;
+  double roundProgress(double progress, {required FrameRate frameRate}) {
+    num? fps;
     if (frameRate == FrameRate.max) {
       return progress;
     } else if (frameRate == FrameRate.composition) {
@@ -200,7 +178,7 @@ class LottieComposition {
   @override
   String toString() {
     final sb = StringBuffer('LottieComposition:\n');
-    for (var layer in _layers) {
+    for (var layer in layers) {
       sb.write(layer.toStringWithPrefix('\t'));
     }
     return sb.toString();

lib/src/l.dart

@@ -3,8 +3,8 @@ import 'dart:developer';
 class L {
   static final int _maxDepth = 20;
   static bool _traceEnabled = false;
-  static List<String> _sections;
-  static List<int> _startTimeNs;
+  static late List<String?> _sections;
+  static late List<int> _startTimeNs;
   static int _traceDepth = 0;
   static int _depthPastMaxDepth = 0;
 

lib/src/lottie.dart

@@ -15,20 +15,20 @@ import 'providers/load_image.dart';
 /// [repeat] and [reverse].
 class Lottie extends StatefulWidget {
   Lottie({
-    Key key,
-    @required this.composition,
+    Key? key,
+    required this.composition,
     this.controller,
     this.width,
     this.height,
     this.alignment,
     this.fit,
-    bool animate,
+    bool? animate,
     this.frameRate,
-    bool repeat,
-    bool reverse,
+    bool? repeat,
+    bool? reverse,
     this.delegates,
     this.options,
-    bool addRepaintBoundary,
+    bool? addRepaintBoundary,
   })  : animate = animate ?? true,
         reverse = reverse ?? false,
         repeat = repeat ?? true,
@@ -38,24 +38,24 @@ class Lottie extends StatefulWidget {
   /// Creates a widget that displays an [LottieComposition] obtained from an [AssetBundle].
   static LottieBuilder asset(
     String name, {
-    Animation<double> controller,
-    bool animate,
-    FrameRate frameRate,
-    bool repeat,
-    bool reverse,
-    LottieDelegates delegates,
-    LottieOptions options,
-    void Function(LottieComposition) onLoaded,
-    LottieImageProviderFactory imageProviderFactory,
-    Key key,
-    AssetBundle bundle,
-    LottieFrameBuilder frameBuilder,
-    double width,
-    double height,
-    BoxFit fit,
-    Alignment alignment,
-    String package,
-    bool addRepaintBoundary,
+    Animation<double>? controller,
+    bool? animate,
+    FrameRate? frameRate,
+    bool? repeat,
+    bool? reverse,
+    LottieDelegates? delegates,
+    LottieOptions? options,
+    void Function(LottieComposition)? onLoaded,
+    LottieImageProviderFactory? imageProviderFactory,
+    Key? key,
+    AssetBundle? bundle,
+    LottieFrameBuilder? frameBuilder,
+    double? width,
+    double? height,
+    BoxFit? fit,
+    Alignment? alignment,
+    String? package,
+    bool? addRepaintBoundary,
   }) =>
       LottieBuilder.asset(
         name,
@@ -82,22 +82,22 @@ class Lottie extends StatefulWidget {
   /// Creates a widget that displays an [LottieComposition] obtained from a [File].
   static LottieBuilder file(
     Object /*io.File|html.File*/ file, {
-    Animation<double> controller,
-    FrameRate frameRate,
-    bool animate,
-    bool repeat,
-    bool reverse,
-    LottieDelegates delegates,
-    LottieOptions options,
-    LottieImageProviderFactory imageProviderFactory,
-    void Function(LottieComposition) onLoaded,
-    Key key,
-    LottieFrameBuilder frameBuilder,
-    double width,
-    double height,
-    BoxFit fit,
-    Alignment alignment,
-    bool addRepaintBoundary,
+    Animation<double>? controller,
+    FrameRate? frameRate,
+    bool? animate,
+    bool? repeat,
+    bool? reverse,
+    LottieDelegates? delegates,
+    LottieOptions? options,
+    LottieImageProviderFactory? imageProviderFactory,
+    void Function(LottieComposition)? onLoaded,
+    Key? key,
+    LottieFrameBuilder? frameBuilder,
+    double? width,
+    double? height,
+    BoxFit? fit,
+    Alignment? alignment,
+    bool? addRepaintBoundary,
   }) =>
       LottieBuilder.file(
         file,
@@ -122,22 +122,22 @@ class Lottie extends StatefulWidget {
   /// Creates a widget that displays an [LottieComposition] obtained from a [Uint8List].
   static LottieBuilder memory(
     Uint8List bytes, {
-    Animation<double> controller,
-    FrameRate frameRate,
-    bool animate,
-    bool repeat,
-    bool reverse,
-    LottieDelegates delegates,
-    LottieOptions options,
-    LottieImageProviderFactory imageProviderFactory,
-    void Function(LottieComposition) onLoaded,
-    Key key,
-    LottieFrameBuilder frameBuilder,
-    double width,
-    double height,
-    BoxFit fit,
-    Alignment alignment,
-    bool addRepaintBoundary,
+    Animation<double>? controller,
+    FrameRate? frameRate,
+    bool? animate,
+    bool? repeat,
+    bool? reverse,
+    LottieDelegates? delegates,
+    LottieOptions? options,
+    LottieImageProviderFactory? imageProviderFactory,
+    void Function(LottieComposition)? onLoaded,
+    Key? key,
+    LottieFrameBuilder? frameBuilder,
+    double? width,
+    double? height,
+    BoxFit? fit,
+    Alignment? alignment,
+    bool? addRepaintBoundary,
   }) =>
       LottieBuilder.memory(
         bytes,
@@ -162,22 +162,22 @@ class Lottie extends StatefulWidget {
   /// Creates a widget that displays an [LottieComposition] obtained from the network.
   static LottieBuilder network(
     String url, {
-    Animation<double> controller,
-    FrameRate frameRate,
-    bool animate,
-    bool repeat,
-    bool reverse,
-    LottieDelegates delegates,
-    LottieOptions options,
-    LottieImageProviderFactory imageProviderFactory,
-    void Function(LottieComposition) onLoaded,
-    Key key,
-    LottieFrameBuilder frameBuilder,
-    double width,
-    double height,
-    BoxFit fit,
-    Alignment alignment,
-    bool addRepaintBoundary,
+    Animation<double>? controller,
+    FrameRate? frameRate,
+    bool? animate,
+    bool? repeat,
+    bool? reverse,
+    LottieDelegates? delegates,
+    LottieOptions? options,
+    LottieImageProviderFactory? imageProviderFactory,
+    void Function(LottieComposition)? onLoaded,
+    Key? key,
+    LottieFrameBuilder? frameBuilder,
+    double? width,
+    double? height,
+    BoxFit? fit,
+    Alignment? alignment,
+    bool? addRepaintBoundary,
   }) =>
       LottieBuilder.network(
         url,
@@ -201,12 +201,12 @@ class Lottie extends StatefulWidget {
 
   /// The Lottie composition to animate.
   /// It could be parsed asynchronously with `LottieComposition.fromBytes`.
-  final LottieComposition composition;
+  final LottieComposition? composition;
 
   /// The animation controller to animate the Lottie animation.
   /// If null, a controller is automatically created by this class and is configured
   /// with the properties [animate], [reverse]
-  final Animation<double> controller;
+  final Animation<double>? controller;
 
   /// The number of frames per second to render.
   /// Use `FrameRate.composition` to use the original frame rate of the Lottie composition (default)
@@ -214,7 +214,7 @@ class Lottie extends StatefulWidget {
   ///
   /// The advantage of using a low frame rate is to preserve the device battery
   /// by doing less rendering work.
-  final FrameRate frameRate;
+  final FrameRate? frameRate;
 
   /// If no controller is specified, this value indicate whether or not the
   /// Lottie animation should be played automatically (default to true).
@@ -237,16 +237,16 @@ class Lottie extends StatefulWidget {
   ///
   /// If null, the composition will pick a size that best preserves its intrinsic
   /// aspect ratio.
-  final double width;
+  final double? width;
 
   /// If non-null, require the composition to have this height.
   ///
   /// If null, the composition will pick a size that best preserves its intrinsic
   /// aspect ratio.
-  final double height;
+  final double? height;
 
   /// How to inscribe the Lottie composition into the space allocated during layout.
-  final BoxFit fit;
+  final BoxFit? fit;
 
   /// How to align the composition within its bounds.
   ///
@@ -266,18 +266,18 @@ class Lottie extends StatefulWidget {
   ///    specify an [AlignmentGeometry].
   ///  * [AlignmentDirectional], like [Alignment] for specifying alignments
   ///    relative to text direction.
-  final AlignmentGeometry alignment;
+  final AlignmentGeometry? alignment;
 
   /// A group of callbacks to further customize the lottie animation.
   /// - A [text] delegate to dynamically change some text displayed in the animation
   /// - A value callback to change the properties of the animation at runtime.
   /// - A text style factory to map between a font family specified in the animation
   ///   and the font family in your assets.
-  final LottieDelegates delegates;
+  final LottieDelegates? delegates;
 
   /// Some options to enable/disable some feature of Lottie
   /// - enableMergePaths: Enable merge path support
-  final LottieOptions options;
+  final LottieOptions? options;
 
   /// Indicate to automatically add a `RepaintBoundary` widget around the animation.
   /// This allows to optimize the app performance by isolating the animation in its
@@ -296,7 +296,7 @@ class Lottie extends StatefulWidget {
 }
 
 class _LottieState extends State<Lottie> with TickerProviderStateMixin {
-  AnimationController _autoAnimation;
+  late AnimationController _autoAnimation;
 
   @override
   void initState() {

lib/src/lottie_builder.dart

@@ -16,7 +16,7 @@ import 'providers/network_provider.dart';
 typedef LottieFrameBuilder = Widget Function(
   BuildContext context,
   Widget child,
-  LottieComposition composition,
+  LottieComposition? composition,
 );
 
 /// A widget that displays a Lottie animation.
@@ -33,8 +33,8 @@ typedef LottieFrameBuilder = Widget Function(
 ///
 class LottieBuilder extends StatefulWidget {
   const LottieBuilder({
-    Key key,
-    @required this.lottie,
+    Key? key,
+    required this.lottie,
     this.controller,
     this.frameRate,
     this.animate,
@@ -49,13 +49,12 @@ class LottieBuilder extends StatefulWidget {
     this.fit,
     this.alignment,
     this.addRepaintBoundary,
-  })  : assert(lottie != null),
-        super(key: key);
+  }) : super(key: key);
 
   /// Creates a widget that displays an [LottieComposition] obtained from the network.
   LottieBuilder.network(
     String src, {
-    Map<String, String> headers,
+    Map<String, String>? headers,
     this.controller,
     this.frameRate,
     this.animate,
@@ -63,9 +62,9 @@ class LottieBuilder extends StatefulWidget {
     this.repeat,
     this.delegates,
     this.options,
-    LottieImageProviderFactory imageProviderFactory,
+    LottieImageProviderFactory? imageProviderFactory,
     this.onLoaded,
-    Key key,
+    Key? key,
     this.frameBuilder,
     this.width,
     this.height,
@@ -95,9 +94,9 @@ class LottieBuilder extends StatefulWidget {
     this.repeat,
     this.delegates,
     this.options,
-    LottieImageProviderFactory imageProviderFactory,
+    LottieImageProviderFactory? imageProviderFactory,
     this.onLoaded,
-    Key key,
+    Key? key,
     this.frameBuilder,
     this.width,
     this.height,
@@ -117,16 +116,16 @@ class LottieBuilder extends StatefulWidget {
     this.repeat,
     this.delegates,
     this.options,
-    LottieImageProviderFactory imageProviderFactory,
+    LottieImageProviderFactory? imageProviderFactory,
     this.onLoaded,
-    Key key,
-    AssetBundle bundle,
+    Key? key,
+    AssetBundle? bundle,
     this.frameBuilder,
     this.width,
     this.height,
     this.fit,
     this.alignment,
-    String package,
+    String? package,
     this.addRepaintBoundary,
   })  : lottie = AssetLottie(name,
             bundle: bundle,
@@ -144,9 +143,9 @@ class LottieBuilder extends StatefulWidget {
     this.repeat,
     this.delegates,
     this.options,
-    LottieImageProviderFactory imageProviderFactory,
+    LottieImageProviderFactory? imageProviderFactory,
     this.onLoaded,
-    Key key,
+    Key? key,
     this.frameBuilder,
     this.width,
     this.height,
@@ -164,45 +163,45 @@ class LottieBuilder extends StatefulWidget {
   /// A callback called when the LottieComposition has been loaded.
   /// You can use this callback to set the correct duration on the AnimationController
   /// with `composition.duration`
-  final void Function(LottieComposition) onLoaded;
+  final void Function(LottieComposition)? onLoaded;
 
   /// The animation controller of the Lottie animation.
   /// The animated value will be mapped to the `progress` property of the
   /// Lottie animation.
-  final Animation<double> controller;
+  final Animation<double>? controller;
 
   /// The number of frames per second to render.
   /// Use `FrameRate.composition` to use the original frame rate of the Lottie composition (default)
   /// Use `FrameRate.max` to advance the animation progression at every frame.
-  final FrameRate frameRate;
+  final FrameRate? frameRate;
 
   /// If no controller is specified, this value indicate whether or not the
   /// Lottie animation should be played automatically (default to true).
   /// If there is an animation controller specified, this property has no effect.
   ///
   /// See [repeat] to control whether the animation should repeat.
-  final bool animate;
+  final bool? animate;
 
   /// Specify that the automatic animation should repeat in a loop (default to true).
   /// The property has no effect if [animate] is false or [controller] is not null.
-  final bool repeat;
+  final bool? repeat;
 
   /// Specify that the automatic animation should repeat in a loop in a "reverse"
   /// mode (go from start to end and then continuously from end to start).
   /// It default to false.
   /// The property has no effect if [animate] is false, [repeat] is false or [controller] is not null.
-  final bool reverse;
+  final bool? reverse;
 
   /// A group of options to further customize the lottie animation.
   /// - A [text] delegate to dynamically change some text displayed in the animation
   /// - A value callback to change the properties of the animation at runtime.
   /// - A text style factory to map between a font family specified in the animation
   ///   and the font family in your assets.
-  final LottieDelegates delegates;
+  final LottieDelegates? delegates;
 
   /// Some options to enable/disable some feature of Lottie
   /// - enableMergePaths: Enable merge path support
-  final LottieOptions options;
+  final LottieOptions? options;
 
   /// A builder function responsible for creating the widget that represents
   /// this lottie animation.
@@ -277,7 +276,7 @@ class LottieBuilder extends StatefulWidget {
   /// ```
   /// {@end-tool}
   ///
-  final LottieFrameBuilder frameBuilder;
+  final LottieFrameBuilder? frameBuilder;
 
   /// If non-null, require the lottie animation to have this width.
   ///
@@ -289,7 +288,7 @@ class LottieBuilder extends StatefulWidget {
   /// layout constraints, so that the animation does not change size as it loads.
   /// Consider using [fit] to adapt the animation's rendering to fit the given width
   /// and height if the exact animation dimensions are not known in advance.
-  final double width;
+  final double? width;
 
   /// If non-null, require the lottie animation to have this height.
   ///
@@ -301,13 +300,13 @@ class LottieBuilder extends StatefulWidget {
   /// layout constraints, so that the animation does not change size as it loads.
   /// Consider using [fit] to adapt the animation's rendering to fit the given width
   /// and height if the exact animation dimensions are not known in advance.
-  final double height;
+  final double? height;
 
   /// How to inscribe the animation into the space allocated during layout.
   ///
   /// The default varies based on the other fields. See the discussion at
   /// [paintImage].
-  final BoxFit fit;
+  final BoxFit? fit;
 
   /// How to align the animation within its bounds.
   ///
@@ -334,14 +333,14 @@ class LottieBuilder extends StatefulWidget {
   ///    specify an [AlignmentGeometry].
   ///  * [AlignmentDirectional], like [Alignment] for specifying alignments
   ///    relative to text direction.
-  final AlignmentGeometry alignment;
+  final AlignmentGeometry? alignment;
 
   /// Indicate to automatically add a `RepaintBoundary` widget around the animation.
   /// This allows to optimize the app performance by isolating the animation in its
   /// own `Layer`.
   ///
   /// This property is `true` by default.
-  final bool addRepaintBoundary;
+  final bool? addRepaintBoundary;
 
   @override
   _LottieBuilderState createState() => _LottieBuilderState();
@@ -361,7 +360,7 @@ class LottieBuilder extends StatefulWidget {
 }
 
 class _LottieBuilderState extends State<LottieBuilder> {
-  Future<LottieComposition> _loadingFuture;
+  Future<LottieComposition>? _loadingFuture;
 
   @override
   void initState() {
@@ -382,11 +381,14 @@ class _LottieBuilderState extends State<LottieBuilder> {
   void _load() {
     var provider = widget.lottie;
     _loadingFuture = widget.lottie.load().then((composition) {
+      print('Loaded');
       if (mounted && widget.onLoaded != null && widget.lottie == provider) {
-        widget.onLoaded(composition);
+        widget.onLoaded!(composition);
       }
 
       return composition;
+    }, onError: (Object e, StackTrace t) {
+      print('Load error $e $t');
     });
   }
 
@@ -397,7 +399,7 @@ class _LottieBuilderState extends State<LottieBuilder> {
       builder: (context, snapshot) {
         if (snapshot.hasError) {
           if (kDebugMode) {
-            return ErrorWidget(snapshot.error);
+            return ErrorWidget(snapshot.error!);
           }
         }
 
@@ -420,7 +422,7 @@ class _LottieBuilderState extends State<LottieBuilder> {
         );
 
         if (widget.frameBuilder != null) {
-          result = widget.frameBuilder(context, result, composition);
+          result = widget.frameBuilder!(context, result, composition);
         }
 
         return result;

lib/src/lottie_delegates.dart

@@ -11,7 +11,7 @@ class LottieDelegates {
   /// Specify a callback to dynamically changes the text displayed in the lottie
   /// animation.
   /// For instance, this is useful when you want to translate the text in the animation.
-  final String Function(String) /*?*/ text;
+  final String Function(String)? text;
 
   /// A callback to map between a font family specified in the json animation
   /// with the font family in your assets.
@@ -24,7 +24,7 @@ class LottieDelegates {
   /// Given an object containing the font family and style specified in the json
   /// return a configured `TextStyle` that will be used as the base style when
   /// painting the text.
-  final TextStyle Function(LottieFontStyle) textStyle;
+  final TextStyle Function(LottieFontStyle)? textStyle;
 
   /// A list of value delegates to dynamically modify the animation
   /// properties at runtime.
@@ -41,13 +41,13 @@ class LottieDelegates {
   ///   ),
   /// );
   /// ```
-  final List<ValueDelegate> values;
+  final List<ValueDelegate>? values;
 
   //TODO(xha): imageDelegate to change the image to display?
 
   LottieDelegates({
     this.text,
-    TextStyle Function(LottieFontStyle) textStyle,
+    TextStyle Function(LottieFontStyle)? textStyle,
     this.values,
   }) : textStyle = textStyle;
 

lib/src/lottie_drawable.dart

@@ -1,4 +1,5 @@
 import 'dart:ui' as ui;
+import 'package:collection/collection.dart' show IterableExtension;
 import 'package:flutter/rendering.dart';
 import 'package:vector_math/vector_math_64.dart';
 import 'composition.dart';
@@ -12,9 +13,9 @@ import 'value_delegate.dart';
 class LottieDrawable {
   final LottieComposition composition;
   final _matrix = Matrix4.identity();
-  CompositionLayer _compositionLayer;
+  late CompositionLayer _compositionLayer;
   final Size size;
-  LottieDelegates _delegates;
+  LottieDelegates? _delegates;
   bool _isDirty = true;
   final bool enableMergePaths;
 
@@ -22,7 +23,7 @@ class LottieDrawable {
   bool antiAliasingSuggested = true;
 
   LottieDrawable(this.composition,
-      {LottieDelegates delegates, bool enableMergePaths})
+      {LottieDelegates? delegates, bool? enableMergePaths})
       : size = Size(composition.bounds.width.toDouble(),
             composition.bounds.height.toDouble()),
         enableMergePaths = enableMergePaths ?? false {
@@ -48,8 +49,8 @@ class LottieDrawable {
   }
 
   double get progress => _progress ?? 0.0;
-  double _progress;
-  bool setProgress(double value, {FrameRate frameRate}) {
+  double? _progress;
+  bool setProgress(double value, {FrameRate? frameRate}) {
     frameRate ??= FrameRate.composition;
     var roundedProgress =
         composition.roundProgress(value, frameRate: frameRate);
@@ -63,8 +64,8 @@ class LottieDrawable {
     }
   }
 
-  LottieDelegates get delegates => _delegates;
-  set delegates(LottieDelegates delegates) {
+  LottieDelegates? get delegates => _delegates;
+  set delegates(LottieDelegates? delegates) {
     if (_delegates != delegates) {
       _delegates = delegates;
       _updateValueDelegates(delegates?.values);
@@ -75,7 +76,7 @@ class LottieDrawable {
     return delegates?.text == null && composition.characters.isNotEmpty;
   }
 
-  ui.Image getImageAsset(String ref) {
+  ui.Image? getImageAsset(String? ref) {
     var imageAsset = composition.images[ref];
     if (imageAsset != null) {
       return imageAsset.loadedImage;
@@ -90,7 +91,7 @@ class LottieDrawable {
   }
 
   List<ValueDelegate> _valueDelegates = <ValueDelegate>[];
-  void _updateValueDelegates(List<ValueDelegate> newDelegates) {
+  void _updateValueDelegates(List<ValueDelegate>? newDelegates) {
     if (identical(_valueDelegates, newDelegates)) return;
 
     newDelegates ??= const [];
@@ -99,14 +100,14 @@ class LottieDrawable {
 
     for (var newDelegate in newDelegates) {
       var existingDelegate = _valueDelegates
-          .firstWhere((f) => f.isSameProperty(newDelegate), orElse: () => null);
+          .firstWhereOrNull((f) => f.isSameProperty(newDelegate));
       if (existingDelegate != null) {
         var resolved = internalResolved(existingDelegate);
         resolved.updateDelegate(newDelegate);
         delegates.add(existingDelegate);
       } else {
         var keyPaths = _resolveKeyPath(KeyPath(newDelegate.keyPath));
-        var resolvedValueDelegate = internalResolve(newDelegate, keyPaths);
+        var resolvedValueDelegate = internalResolve(newDelegate, keyPaths)!;
         resolvedValueDelegate.addValueCallback(this);
         delegates.add(newDelegate);
       }
@@ -132,7 +133,8 @@ class LottieDrawable {
     return keyPaths;
   }
 
-  void draw(ui.Canvas canvas, ui.Rect rect, {BoxFit fit, Alignment alignment}) {
+  void draw(ui.Canvas canvas, ui.Rect rect,
+      {BoxFit? fit, Alignment? alignment}) {
     if (rect.isEmpty) {
       return;
     }
@@ -165,5 +167,5 @@ class LottieDrawable {
 class LottieFontStyle {
   final String fontFamily, style;
 
-  LottieFontStyle({this.fontFamily, this.style});
+  LottieFontStyle({required this.fontFamily, required this.style});
 }

lib/src/lottie_image_asset.dart

@@ -6,10 +6,14 @@ class LottieImageAsset {
   final String id;
   final String fileName;
   final String dirName;
-  ui.Image loadedImage;
+  ui.Image? loadedImage;
 
   LottieImageAsset(
-      {this.width, this.height, this.id, this.fileName, this.dirName});
+      {required this.width,
+      required this.height,
+      required this.id,
+      required this.fileName,
+      required this.dirName});
 
   @override
   String toString() =>

lib/src/model/animatable/animatable_text_properties.dart

@@ -2,10 +2,10 @@ import 'animatable_color_value.dart';
 import 'animatable_double_value.dart';
 
 class AnimatableTextProperties {
-  final AnimatableColorValue /*?*/ color;
-  final AnimatableColorValue /*?*/ stroke;
-  final AnimatableDoubleValue /*?*/ strokeWidth;
-  final AnimatableDoubleValue /*?*/ tracking;
+  final AnimatableColorValue? color;
+  final AnimatableColorValue? stroke;
+  final AnimatableDoubleValue? strokeWidth;
+  final AnimatableDoubleValue? tracking;
 
   AnimatableTextProperties(
       {this.color, this.stroke, this.strokeWidth, this.tracking});

lib/src/model/animatable/animatable_transform.dart

@@ -12,25 +12,25 @@ import 'animatable_scale_value.dart';
 import 'animatable_value.dart';
 
 class AnimatableTransform implements ModifierContent, ContentModel {
-  final AnimatablePathValue /*?*/ anchorPoint;
+  final AnimatablePathValue? anchorPoint;
 
-  final AnimatableValue<Offset, Offset> /*?*/ position;
+  final AnimatableValue<Offset, Offset>? position;
 
-  final AnimatableScaleValue /*?*/ scale;
+  final AnimatableScaleValue? scale;
 
-  final AnimatableDoubleValue /*?*/ rotation;
+  final AnimatableDoubleValue? rotation;
 
-  final AnimatableIntegerValue /*?*/ opacity;
+  final AnimatableIntegerValue? opacity;
 
-  final AnimatableDoubleValue /*?*/ skew;
+  final AnimatableDoubleValue? skew;
 
-  final AnimatableDoubleValue /*?*/ skewAngle;
+  final AnimatableDoubleValue? skewAngle;
 
   // Used for repeaters
 
-  final AnimatableDoubleValue /*?*/ startOpacity;
+  final AnimatableDoubleValue? startOpacity;
 
-  final AnimatableDoubleValue /*?*/ endOpacity;
+  final AnimatableDoubleValue? endOpacity;
 
   AnimatableTransform(
       {this.anchorPoint,
@@ -48,7 +48,7 @@ class AnimatableTransform implements ModifierContent, ContentModel {
   }
 
   @override
-  Content /*?*/ toContent(LottieDrawable drawable, BaseLayer layer) {
+  Content? toContent(LottieDrawable drawable, BaseLayer layer) {
     return null;
   }
 }

lib/src/model/animatable/animatable_value.dart

@@ -1,7 +1,7 @@
 import '../../animation/keyframe/base_keyframe_animation.dart';
 import '../../value/keyframe.dart';
 
-abstract class AnimatableValue<K, A> {
+abstract class AnimatableValue<K extends Object, A extends Object> {
   List<Keyframe<K>> get keyframes;
   bool get isStatic;
   BaseKeyframeAnimation<K, A> createAnimation();

lib/src/model/animatable/base_animatable_value.dart

@@ -1,7 +1,8 @@
 import '../../value/keyframe.dart';
 import 'animatable_value.dart';
 
-abstract class BaseAnimatableValue<V, O> implements AnimatableValue<V, O> {
+abstract class BaseAnimatableValue<V extends Object, O extends Object>
+    implements AnimatableValue<V, O> {
   @override
   final List<Keyframe<V>> keyframes;
 

lib/src/model/content/circle_shape.dart

@@ -8,14 +8,18 @@ import '../layer/base_layer.dart';
 import 'content_model.dart';
 
 class CircleShape implements ContentModel {
-  final String name;
+  final String? name;
   final AnimatableValue<Offset, Offset> position;
   final AnimatablePointValue size;
   final bool isReversed;
   final bool hidden;
 
   CircleShape(
-      {this.name, this.position, this.size, this.isReversed, this.hidden});
+      {this.name,
+      required this.position,
+      required this.size,
+      required this.isReversed,
+      required this.hidden});
 
   @override
   Content toContent(LottieDrawable drawable, BaseLayer layer) {

lib/src/model/content/content_model.dart

@@ -3,5 +3,5 @@ import '../../lottie_drawable.dart';
 import '../layer/base_layer.dart';
 
 abstract class ContentModel {
-  Content /*?*/ toContent(LottieDrawable drawable, BaseLayer layer);
+  Content? toContent(LottieDrawable drawable, BaseLayer layer);
 }

lib/src/model/content/gradient_color.dart

@@ -16,7 +16,7 @@ class GradientColor {
     }
 
     for (var i = 0; i < gc1.colors.length; i++) {
-      positions[i] = lerpDouble(gc1.positions[i], gc2.positions[i], progress);
+      positions[i] = lerpDouble(gc1.positions[i], gc2.positions[i], progress)!;
       colors[i] =
           GammaEvaluator.evaluate(progress, gc1.colors[i], gc2.colors[i]);
     }

lib/src/model/content/gradient_fill.dart

@@ -11,28 +11,28 @@ import 'content_model.dart';
 import 'gradient_type.dart';
 
 class GradientFill implements ContentModel {
-  final String name;
+  final String? name;
   final GradientType gradientType;
   final PathFillType fillType;
   final AnimatableGradientColorValue gradientColor;
   final AnimatableIntegerValue opacity;
   final AnimatablePointValue startPoint;
   final AnimatablePointValue endPoint;
-  final AnimatableDoubleValue /*?*/ highlightLength;
-  final AnimatableDoubleValue /*?*/ highlightAngle;
+  final AnimatableDoubleValue? highlightLength;
+  final AnimatableDoubleValue? highlightAngle;
   final bool hidden;
 
   GradientFill({
     this.name,
-    this.gradientType,
-    this.fillType,
-    this.gradientColor,
-    this.opacity,
-    this.startPoint,
-    this.endPoint,
+    required this.gradientType,
+    required this.fillType,
+    required this.gradientColor,
+    required this.opacity,
+    required this.startPoint,
+    required this.endPoint,
     this.highlightLength,
     this.highlightAngle,
-    this.hidden,
+    required this.hidden,
   });
 
   @override

lib/src/model/content/gradient_stroke.dart

@@ -11,34 +11,34 @@ import 'gradient_type.dart';
 import 'shape_stroke.dart';
 
 class GradientStroke implements ContentModel {
-  final String name;
+  final String? name;
   final GradientType gradientType;
   final AnimatableGradientColorValue gradientColor;
   final AnimatableIntegerValue opacity;
   final AnimatablePointValue startPoint;
   final AnimatablePointValue endPoint;
   final AnimatableDoubleValue width;
-  final LineCapType capType;
-  final LineJoinType joinType;
+  final LineCapType? capType;
+  final LineJoinType? joinType;
   final double miterLimit;
   final List<AnimatableDoubleValue> lineDashPattern;
-  final AnimatableDoubleValue /*?*/ dashOffset;
+  final AnimatableDoubleValue? dashOffset;
   final bool hidden;
 
   GradientStroke({
     this.name,
-    this.gradientType,
-    this.gradientColor,
-    this.opacity,
-    this.startPoint,
-    this.endPoint,
-    this.width,
+    required this.gradientType,
+    required this.gradientColor,
+    required this.opacity,
+    required this.startPoint,
+    required this.endPoint,
+    required this.width,
     this.capType,
     this.joinType,
-    this.miterLimit,
-    this.lineDashPattern,
+    required this.miterLimit,
+    required this.lineDashPattern,
     this.dashOffset,
-    this.hidden,
+    required this.hidden,
   });
 
   @override

lib/src/model/content/mask.dart

@@ -1,4 +1,3 @@
-import 'package:meta/meta.dart';
 import '../animatable/animatable_integer_value.dart';
 import '../animatable/animatable_shape_value.dart';
 
@@ -16,8 +15,8 @@ class Mask {
   final bool isInverted;
 
   Mask(
-      {@required this.maskMode,
-      @required this.maskPath,
-      @required this.opacity,
-      @required this.isInverted});
+      {required this.maskMode,
+      required this.maskPath,
+      required this.opacity,
+      required this.isInverted});
 }

lib/src/model/content/merge_paths.dart

@@ -12,10 +12,10 @@ class MergePaths implements ContentModel {
   final MergePathsMode mode;
   final bool hidden;
 
-  MergePaths({this.name, this.mode, this.hidden});
+  MergePaths({required this.name, required this.mode, required this.hidden});
 
   @override
-  Content /*?*/ toContent(LottieDrawable drawable, BaseLayer layer) {
+  Content? toContent(LottieDrawable drawable, BaseLayer layer) {
     if (!drawable.enableMergePaths) {
       logger.warning('Animation contains merge paths but they are disabled.');
       return null;

lib/src/model/content/polystar_shape.dart

@@ -16,7 +16,7 @@ class PolystarShapeType {
 
   const PolystarShapeType(this.value);
 
-  static PolystarShapeType forValue(int value) {
+  static PolystarShapeType? forValue(int value) {
     for (var type in values) {
       if (type.value == value) {
         return type;
@@ -27,28 +27,28 @@ class PolystarShapeType {
 }
 
 class PolystarShape implements ContentModel {
-  final String name;
-  final PolystarShapeType type;
+  final String? name;
+  final PolystarShapeType? type;
   final AnimatableDoubleValue points;
   final AnimatableValue<Offset, Offset> position;
   final AnimatableDoubleValue rotation;
-  final AnimatableDoubleValue innerRadius;
+  final AnimatableDoubleValue? innerRadius;
   final AnimatableDoubleValue outerRadius;
-  final AnimatableDoubleValue innerRoundedness;
+  final AnimatableDoubleValue? innerRoundedness;
   final AnimatableDoubleValue outerRoundedness;
   final bool hidden;
 
   PolystarShape({
     this.name,
     this.type,
-    this.points,
-    this.position,
-    this.rotation,
+    required this.points,
+    required this.position,
+    required this.rotation,
     this.innerRadius,
-    this.outerRadius,
+    required this.outerRadius,
     this.innerRoundedness,
-    this.outerRoundedness,
-    this.hidden,
+    required this.outerRoundedness,
+    required this.hidden,
   });
 
   @override

lib/src/model/content/rectangle_shape.dart

@@ -9,14 +9,18 @@ import '../layer/base_layer.dart';
 import 'content_model.dart';
 
 class RectangleShape implements ContentModel {
-  final String name;
+  final String? name;
   final AnimatableValue<Offset, Offset> position;
   final AnimatablePointValue size;
   final AnimatableDoubleValue cornerRadius;
   final bool hidden;
 
   RectangleShape(
-      {this.name, this.position, this.size, this.cornerRadius, this.hidden});
+      {this.name,
+      required this.position,
+      required this.size,
+      required this.cornerRadius,
+      required this.hidden});
 
   @override
   Content toContent(LottieDrawable drawable, BaseLayer layer) {

lib/src/model/content/repeater.dart

@@ -7,16 +7,21 @@ import '../layer/base_layer.dart';
 import 'content_model.dart';
 
 class Repeater implements ContentModel {
-  final String name;
+  final String? name;
   final AnimatableDoubleValue copies;
   final AnimatableDoubleValue offset;
   final AnimatableTransform transform;
   final bool hidden;
 
-  Repeater({this.name, this.copies, this.offset, this.transform, this.hidden});
+  Repeater(
+      {this.name,
+      required this.copies,
+      required this.offset,
+      required this.transform,
+      required this.hidden});
 
   @override
-  Content /*?*/ toContent(LottieDrawable drawable, BaseLayer layer) {
+  Content? toContent(LottieDrawable drawable, BaseLayer layer) {
     return RepeaterContent(drawable, layer, this);
   }
 }

lib/src/model/content/shape_data.dart

@@ -8,7 +8,7 @@ class ShapeData {
   Offset _initialPoint;
   bool _closed;
 
-  ShapeData(List<CubicCurveData> curves, {Offset initialPoint, bool closed})
+  ShapeData(List<CubicCurveData> curves, {Offset? initialPoint, bool? closed})
       : curves = curves.toList(),
         _initialPoint = initialPoint ?? Offset.zero,
         _closed = closed ?? false;
@@ -51,8 +51,8 @@ class ShapeData {
     var initialPoint1 = shapeData1.initialPoint;
     var initialPoint2 = shapeData2.initialPoint;
 
-    setInitialPoint(lerpDouble(initialPoint1.dx, initialPoint2.dx, percentage),
-        lerpDouble(initialPoint1.dy, initialPoint2.dy, percentage));
+    setInitialPoint(lerpDouble(initialPoint1.dx, initialPoint2.dx, percentage)!,
+        lerpDouble(initialPoint1.dy, initialPoint2.dy, percentage)!);
 
     for (var i = curves.length - 1; i >= 0; i--) {
       var curve1 = shapeData1.curves[i];
@@ -66,12 +66,14 @@ class ShapeData {
       var cp22 = curve2.controlPoint2;
       var vertex2 = curve2.vertex;
 
-      curves[i].controlPoint1 = Offset(lerpDouble(cp11.dx, cp12.dx, percentage),
-          lerpDouble(cp11.dy, cp12.dy, percentage));
-      curves[i].controlPoint2 = Offset(lerpDouble(cp21.dx, cp22.dx, percentage),
-          lerpDouble(cp21.dy, cp22.dy, percentage));
-      curves[i].vertex = Offset(lerpDouble(vertex1.dx, vertex2.dx, percentage),
-          lerpDouble(vertex1.dy, vertex2.dy, percentage));
+      curves[i].controlPoint1 = Offset(
+          lerpDouble(cp11.dx, cp12.dx, percentage)!,
+          lerpDouble(cp11.dy, cp12.dy, percentage)!);
+      curves[i].controlPoint2 = Offset(
+          lerpDouble(cp21.dx, cp22.dx, percentage)!,
+          lerpDouble(cp21.dy, cp22.dy, percentage)!);
+      curves[i].vertex = Offset(lerpDouble(vertex1.dx, vertex2.dx, percentage)!,
+          lerpDouble(vertex1.dy, vertex2.dy, percentage)!);
     }
   }
 

lib/src/model/content/shape_fill.dart

@@ -10,18 +10,18 @@ import 'content_model.dart';
 class ShapeFill implements ContentModel {
   final bool fillEnabled;
   final PathFillType fillType;
-  final String name;
-  final AnimatableColorValue /*?*/ color;
-  final AnimatableIntegerValue /*?*/ opacity;
+  final String? name;
+  final AnimatableColorValue? color;
+  final AnimatableIntegerValue? opacity;
   final bool hidden;
 
   ShapeFill(
-      {this.fillEnabled,
-      this.fillType,
+      {required this.fillEnabled,
+      required this.fillType,
       this.name,
       this.color,
       this.opacity,
-      this.hidden});
+      required this.hidden});
 
   @override
   Content toContent(LottieDrawable drawable, BaseLayer layer) {