diff --git a/lib/folder_views/common_types.dart b/lib/folder_views/common_types.dart
new file mode 100644
index 00000000..5de02208
--- /dev/null
+++ b/lib/folder_views/common_types.dart
@@ -0,0 +1,6 @@
+enum FolderViewType {
+  Standard,
+  Journal,
+  Card,
+  Grid,
+}
diff --git a/lib/screens/feature_timeline_screen.dart b/lib/screens/feature_timeline_screen.dart
index 71e3795a..4e413080 100644
--- a/lib/screens/feature_timeline_screen.dart
+++ b/lib/screens/feature_timeline_screen.dart
@@ -1,5 +1,3 @@
-// @dart=2.9
-
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 
@@ -55,7 +53,7 @@ class FeatureTile extends StatelessWidget {
       subtitle += ' - ' + feature.subtitle;
     }
 
-    Color color;
+    late Color color;
     var theme = Theme.of(context);
 
     if (feature.pro) {
@@ -82,19 +80,19 @@ class _Tile extends StatelessWidget {
   final Color iconColor;
 
   _Tile({
-    @required this.title,
-    @required this.subTitle,
-    @required this.iconText,
-    @required this.iconColor,
+    required this.title,
+    required this.subTitle,
+    required this.iconText,
+    required this.iconColor,
   });
 
   @override
   Widget build(BuildContext context) {
     var theme = Theme.of(context);
     var textTheme = theme.textTheme;
-    var titleTextStyle = textTheme.subtitle1.copyWith();
-    var subTitleTextStyle = textTheme.bodyText2.copyWith(
-      color: textTheme.caption.color,
+    var titleTextStyle = textTheme.subtitle1!.copyWith();
+    var subTitleTextStyle = textTheme.bodyText2!.copyWith(
+      color: textTheme.caption!.color,
     );
 
     return Container(
@@ -137,7 +135,7 @@ class _Tile extends StatelessWidget {
 
 class _Sign extends StatelessWidget {
   final String text;
-  final Color color;
+  final Color? color;
 
   _Sign(this.text, this.color);
 
@@ -146,7 +144,7 @@ class _Sign extends StatelessWidget {
     var theme = Theme.of(context);
     var textStyle = theme.textTheme.subtitle2;
     if (color != null) {
-      textStyle = textStyle.copyWith(color: color);
+      textStyle = textStyle!.copyWith(color: color);
     }
 
     return Text(text, style: textStyle);
diff --git a/lib/screens/home_screen.dart b/lib/screens/home_screen.dart
index e830c078..6788bdec 100644
--- a/lib/screens/home_screen.dart
+++ b/lib/screens/home_screen.dart
@@ -1,4 +1,4 @@
-// @dart=2.9
+
 
 import 'package:flutter/material.dart';
 
@@ -17,8 +17,8 @@ class HomeScreen extends StatefulWidget {
 }
 
 class _HomeScreenState extends State<HomeScreen> {
-  NotesFolder notesFolder;
-  NotesFolderFS rootFolder;
+  NotesFolder? notesFolder;
+  NotesFolderFS? rootFolder;
 
   @override
   void initState() {
diff --git a/lib/screens/settings_display_images.dart b/lib/screens/settings_display_images.dart
index 4882572f..89e838fd 100644
--- a/lib/screens/settings_display_images.dart
+++ b/lib/screens/settings_display_images.dart
@@ -1,5 +1,3 @@
-// @dart=2.9
-
 /*
 Copyright 2020-2021 Roland Fredenhagen <important@van-fredenhagen.de>
 
@@ -93,7 +91,7 @@ class SettingsDisplayImagesScreenState
                       )
                     : Text(
                         NumberFormat("##.0").format(settings.maxImageZoom),
-                        style: theme.textTheme.subtitle2
+                        style: theme.textTheme.subtitle2!
                             .copyWith(color: theme.accentColor),
                         textAlign: TextAlign.center,
                       ))
diff --git a/lib/screens/settings_widgets.dart b/lib/screens/settings_widgets.dart
index f3557814..51af21ed 100644
--- a/lib/screens/settings_widgets.dart
+++ b/lib/screens/settings_widgets.dart
@@ -1,21 +1,19 @@
-// @dart=2.9
-
 import 'package:flutter/material.dart';
 
 import 'package:easy_localization/easy_localization.dart';
 
 class ListPreference extends StatelessWidget {
   final String title;
-  final String currentOption;
+  final String? currentOption;
   final List<String> options;
   final Function onChange;
   final bool enabled;
 
   ListPreference({
-    @required this.title,
-    @required this.currentOption,
-    @required this.options,
-    @required this.onChange,
+    required this.title,
+    required this.currentOption,
+    required this.options,
+    required this.onChange,
     this.enabled = true,
   });
 
@@ -23,14 +21,14 @@ class ListPreference extends StatelessWidget {
   Widget build(BuildContext context) {
     return ListTile(
       title: Text(title),
-      subtitle: Text(currentOption),
+      subtitle: Text(currentOption!),
       onTap: () async {
         var option = await showDialog<String>(
             context: context,
             builder: (BuildContext context) {
               var children = <Widget>[];
               for (var o in options) {
-                var tile = LabeledRadio(
+                var tile = _LabeledRadio(
                   label: o,
                   value: o,
                   groupValue: currentOption,
@@ -66,17 +64,17 @@ class ListPreference extends StatelessWidget {
   }
 }
 
-class LabeledRadio extends StatelessWidget {
-  const LabeledRadio({
-    this.label,
-    this.groupValue,
-    this.value,
-    this.onChanged,
+class _LabeledRadio extends StatelessWidget {
+  const _LabeledRadio({
+    required this.label,
+    required this.groupValue,
+    required this.value,
+    required this.onChanged,
   });
 
   final String label;
-  final String groupValue;
-  final String value;
+  final String? groupValue;
+  final String? value;
   final Function onChanged;
 
   @override
@@ -87,10 +85,10 @@ class LabeledRadio extends StatelessWidget {
       },
       child: Row(
         children: <Widget>[
-          Radio<String>(
+          Radio<String?>(
             groupValue: groupValue,
             value: value,
-            onChanged: onChanged,
+            onChanged: onChanged as void Function(String?)?,
           ),
           Text(label),
         ],
diff --git a/lib/screens/signup_screen.dart b/lib/screens/signup_screen.dart
index e86ba992..f7993e9d 100644
--- a/lib/screens/signup_screen.dart
+++ b/lib/screens/signup_screen.dart
@@ -1,11 +1,9 @@
-// @dart=2.9
-
 import 'package:flutter/material.dart';
 
 import 'package:gitjournal/screens/login_screen.dart';
 
 class SignUpScreen extends StatefulWidget {
-  SignUpScreen({Key key}) : super(key: key);
+  SignUpScreen({Key? key}) : super(key: key);
 
   @override
   _SignUpScreenState createState() => _SignUpScreenState();
diff --git a/lib/screens/tag_listing.dart b/lib/screens/tag_listing.dart
index cbac3279..db72edb4 100644
--- a/lib/screens/tag_listing.dart
+++ b/lib/screens/tag_listing.dart
@@ -1,4 +1,4 @@
-// @dart=2.9
+
 
 import 'package:flutter/material.dart';
 
@@ -60,7 +60,7 @@ class TagListingScreen extends StatelessWidget {
 
   Widget _buildTagTile(BuildContext context, String tag) {
     var theme = Theme.of(context);
-    var titleColor = theme.textTheme.headline1.color;
+    var titleColor = theme.textTheme.headline1!.color;
 
     return ListTile(
       leading: FaIcon(FontAwesomeIcons.tag, color: titleColor),
diff --git a/lib/setup/error.dart b/lib/setup/error.dart
index c0c09b67..d934c435 100644
--- a/lib/setup/error.dart
+++ b/lib/setup/error.dart
@@ -1,5 +1,3 @@
-// @dart=2.9
-
 import 'package:flutter/material.dart';
 
 import 'package:easy_localization/easy_localization.dart';