Migrate examples to null-safety (#707)

examples/analysis_options.yaml

@@ -134,7 +134,7 @@ linter:
 
 dart_code_metrics:
   rules:
-    - prefer-trailing-comma
+    #- prefer-trailing-comma TODO(luan) this is broken on NS
     - prefer-trailing-comma-for-collection
     - no-equal-then-else
     - no-object-declaration
@@ -143,7 +143,7 @@ dart_code_metrics:
     - test/**
   metrics:
     number-of-arguments: 8
-    number-of-methods: 28
+    number-of-methods: 32
     lines-of-executable-code: 200
     cyclomatic-complexity: 36
 

examples/lib/stories/animations/basic.dart

@@ -6,9 +6,9 @@ import 'package:flame/gestures.dart';
 import 'package:flutter/gestures.dart' show TapDownDetails;
 
 class BasicAnimations extends BaseGame with TapDetector {
-  Image chopper;
+  late Image chopper;
-  Image creature;
+  late Image creature;
-  SpriteAnimation animation;
+  late SpriteAnimation animation;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/components/composability.dart

@@ -32,14 +32,15 @@ class ParentSquare extends Square {
 }
 
 class Composability extends BaseGame {
-  ParentSquare _parent;
+  late ParentSquare _parent;
 
   @override
   bool debugMode = true;
 
-  Composability() {
+  @override
-    _parent = ParentSquare(Vector2.all(200), Vector2.all(300));
+  Future<void> onLoad() async {
-    _parent.anchor = Anchor.center;
+    _parent = ParentSquare(Vector2.all(200), Vector2.all(300))
+      ..anchor = Anchor.center;
     add(_parent);
   }
 

examples/lib/stories/components/debug.dart

@@ -20,14 +20,14 @@ class LogoCompomnent extends SpriteComponent with HasGameRef<DebugGame> {
     final rect = toRect();
 
     if ((x <= 0 && xDirection == -1) ||
-        (rect.right >= gameRef.size.x && xDirection == 1)) {
+        (rect.right >= gameRef!.size.x && xDirection == 1)) {
       xDirection = xDirection * -1;
     }
 
     y += yDirection * speed * dt;
 
     if ((y <= 0 && yDirection == -1) ||
-        (rect.bottom >= gameRef.size.y && yDirection == 1)) {
+        (rect.bottom >= gameRef!.size.y && yDirection == 1)) {
       yDirection = yDirection * -1;
     }
   }

examples/lib/stories/controls/draggables.dart

@@ -11,13 +11,13 @@ class DraggableSquare extends PositionComponent
   @override
   bool debugMode = true;
 
-  DraggableSquare({Vector2 position})
+  DraggableSquare({Vector2? position})
       : super(
           position: position ?? Vector2.all(100),
           size: Vector2.all(100),
         );
 
-  Vector2 dragDeltaPosition;
+  Vector2? dragDeltaPosition;
   bool get isDragging => dragDeltaPosition != null;
 
   @override
@@ -34,7 +34,12 @@ class DraggableSquare extends PositionComponent
 
   @override
   bool onDragUpdate(int pointerId, DragUpdateDetails details) {
-    final localCoords = gameRef.convertGlobalToLocalCoordinate(
+    final dragDeltaPosition = this.dragDeltaPosition;
+    if (dragDeltaPosition == null) {
+      return false;
+    }
+
+    final localCoords = gameRef!.convertGlobalToLocalCoordinate(
       details.globalPosition.toVector2(),
     );
     position = localCoords - dragDeltaPosition;

examples/lib/stories/controls/joystick_player.dart

@@ -17,29 +17,24 @@ class JoystickPlayer extends Component implements JoystickListener {
 
   double currentSpeed = 0;
   double angle = 0;
-  bool _move = false;
+  bool move = false;
-  Paint _paint;
+  Paint paint;
-  Rect _rect;
+  late Rect rect;
 
-  JoystickPlayer() {
+  JoystickPlayer() : paint = _whitePaint;
-    _paint = _whitePaint;
-  }
 
   @override
   void render(Canvas canvas) {
-    if (_rect == null) {
+    canvas.translate(rect.center.dx, rect.center.dy);
-      return;
-    }
-    canvas.translate(_rect.center.dx, _rect.center.dy);
     canvas.rotate(angle == 0.0 ? 0.0 : angle + (pi / 2));
-    canvas.translate(-_rect.center.dx, -_rect.center.dy);
+    canvas.translate(-rect.center.dx, -rect.center.dy);
-    canvas.drawRect(_rect, _paint);
+    canvas.drawRect(rect, paint);
   }
 
   @override
   void update(double dt) {
     super.update(dt);
-    if (_move) {
+    if (move) {
       moveFromAngle(dt);
     }
   }
@@ -47,7 +42,7 @@ class JoystickPlayer extends Component implements JoystickListener {
   @override
   void onGameResize(Vector2 gameSize) {
     final offset = (gameSize - size) / 2;
-    _rect = offset & size;
+    rect = offset & size;
     super.onGameResize(gameSize);
   }
 
@@ -55,33 +50,29 @@ class JoystickPlayer extends Component implements JoystickListener {
   void joystickAction(JoystickActionEvent event) {
     if (event.event == ActionEvent.down) {
       if (event.id == 1) {
-        _paint = _paint == _whitePaint ? _bluePaint : _whitePaint;
+        paint = paint == _whitePaint ? _bluePaint : _whitePaint;
       }
       if (event.id == 2) {
-        _paint = _paint == _whitePaint ? _greenPaint : _whitePaint;
+        paint = paint == _whitePaint ? _greenPaint : _whitePaint;
       }
     } else if (event.event == ActionEvent.move) {
       if (event.id == 3) {
-        angle = event.angle ?? angle;
+        angle = event.angle;
       }
     }
   }
 
   @override
   void joystickChangeDirectional(JoystickDirectionalEvent event) {
-    _move = event.directional != JoystickMoveDirectional.idle;
+    move = event.directional != JoystickMoveDirectional.idle;
-    if (_move) {
+    if (move) {
       angle = event.angle;
       currentSpeed = speed * event.intensity;
     }
   }
 
   void moveFromAngle(double dtUpdate) {
-    if (_rect == null) {
-      return;
-    }
-
     final next = Vector2(cos(angle), sin(angle)) * (currentSpeed * dtUpdate);
-    _rect = _rect.shift(next.toOffset());
+    rect = rect.shift(next.toOffset());
   }
 }

examples/lib/stories/controls/keyboard.dart

@@ -6,21 +6,21 @@ import 'package:flame/palette.dart';
 import 'package:flutter/services.dart' show RawKeyDownEvent, RawKeyEvent;
 
 class KeyboardGame extends Game with KeyboardEvents {
-  static final Paint _white = BasicPalette.white.paint;
+  static final Paint white = BasicPalette.white.paint;
   static const int speed = 200;
 
-  Rect _rect = const Rect.fromLTWH(0, 100, 100, 100);
+  Rect rect = const Rect.fromLTWH(0, 100, 100, 100);
   final Vector2 velocity = Vector2(0, 0);
 
   @override
   void update(double dt) {
     final displacement = velocity * (speed * dt);
-    _rect = _rect.translate(displacement.x, displacement.y);
+    rect = rect.translate(displacement.x, displacement.y);
   }
 
   @override
   void render(Canvas canvas) {
-    canvas.drawRect(_rect, _white);
+    canvas.drawRect(rect, white);
   }
 
   @override

examples/lib/stories/controls/mouse_movement.dart

@@ -7,37 +7,39 @@ import 'package:flutter/material.dart';
 
 class MouseMovementGame extends BaseGame with MouseMovementDetector {
   static const speed = 200;
-  static final Paint _blue = Paint()..color = const Color(0xFF0000FF);
+  static final Paint blue = Paint()..color = const Color(0xFF0000FF);
-  static final Vector2 _size = Vector2.all(50);
+  static final Paint white = BasicPalette.white.paint;
+  static final Vector2 objSize = Vector2.all(50);
 
   Vector2 position = Vector2(0, 0);
-  Vector2 target;
+  Vector2? target;
 
-  bool _onTarget = false;
+  bool onTarget = false;
 
   @override
   void onMouseMove(PointerHoverEvent event) {
     target = event.localPosition.toVector2();
   }
 
-  Rect _toRect() => position.toPositionedRect(_size);
+  Rect _toRect() => position.toPositionedRect(objSize);
 
   @override
   void render(Canvas canvas) {
     super.render(canvas);
     canvas.drawRect(
       _toRect(),
-      _onTarget ? _blue : BasicPalette.white.paint,
+      onTarget ? blue : white,
     );
   }
 
   @override
   void update(double dt) {
+    final target = this.target;
     super.update(dt);
     if (target != null) {
-      _onTarget = _toRect().contains(target.toOffset());
+      onTarget = _toRect().contains(target.toOffset());
 
-      if (!_onTarget) {
+      if (!onTarget) {
         final dir = (target - position).normalized();
         position += dir * (speed * dt);
       }

examples/lib/stories/controls/multitap.dart

@@ -6,32 +6,32 @@ import 'package:flutter/material.dart';
 
 /// Includes an example including advanced detectors
 class MultitapGame extends BaseGame with MultiTouchTapDetector {
-  static final _whitePaint = BasicPalette.white.paint;
+  static final whitePaint = BasicPalette.white.paint;
-  static final _size = Vector2.all(50);
+  static final tapSize = Vector2.all(50);
 
-  final Map<int, Rect> _taps = {};
+  final Map<int, Rect> taps = {};
 
   @override
   void onTapDown(int pointerId, TapDownDetails details) {
-    _taps[pointerId] =
+    taps[pointerId] =
-        details.globalPosition.toVector2().toPositionedRect(_size);
+        details.globalPosition.toVector2().toPositionedRect(tapSize);
   }
 
   @override
   void onTapUp(int pointerId, _) {
-    _taps.remove(pointerId);
+    taps.remove(pointerId);
   }
 
   @override
   void onTapCancel(int pointerId) {
-    _taps.remove(pointerId);
+    taps.remove(pointerId);
   }
 
   @override
   void render(Canvas canvas) {
     super.render(canvas);
-    _taps.values.forEach((rect) {
+    taps.values.forEach((rect) {
-      canvas.drawRect(rect, _whitePaint);
+      canvas.drawRect(rect, whitePaint);
     });
   }
 }

examples/lib/stories/controls/multitap_advanced.dart

@@ -7,65 +7,67 @@ import 'package:flutter/material.dart';
 /// Showcases how to mix two advanced detectors
 class MultitapAdvancedGame extends BaseGame
     with MultiTouchTapDetector, MultiTouchDragDetector {
-  static final _whitePaint = BasicPalette.white.paint;
+  static final whitePaint = BasicPalette.white.paint;
-  static final _size = Vector2.all(50);
+  static final tapSize = Vector2.all(50);
 
-  final Map<int, Rect> _taps = {};
+  final Map<int, Rect> taps = {};
 
-  Vector2 _start;
+  Vector2? start;
-  Vector2 _end;
+  Vector2? end;
-  Rect _panRect;
+  Rect? panRect;
 
   @override
   void onTapDown(int pointerId, TapDownDetails details) {
-    _taps[pointerId] =
+    taps[pointerId] =
-        details.globalPosition.toVector2().toPositionedRect(_size);
+        details.globalPosition.toVector2().toPositionedRect(tapSize);
   }
 
   @override
   void onTapUp(int pointerId, _) {
-    _taps.remove(pointerId);
+    taps.remove(pointerId);
   }
 
   @override
   void onTapCancel(int pointerId) {
-    _taps.remove(pointerId);
+    taps.remove(pointerId);
   }
 
   @override
   void onDragCancel(int pointerId) {
-    _end = null;
+    end = null;
-    _start = null;
+    start = null;
-    _panRect = null;
+    panRect = null;
   }
 
   @override
   void onDragStart(int pointerId, Vector2 position) {
-    _end = null;
+    end = null;
-    _start = position;
+    start = position;
   }
 
   @override
   void onDragUpdate(int pointerId, DragUpdateDetails details) {
-    _end = details.localPosition.toVector2();
+    end = details.localPosition.toVector2();
   }
 
   @override
   void onDragEnd(int pointerId, DragEndDetails details) {
-    if (_start != null && _end != null) {
+    final start = this.start, end = this.end;
-      _panRect = _start.toPositionedRect(_end - _start);
+    if (start != null && end != null) {
+      panRect = start.toPositionedRect(end - start);
     }
   }
 
   @override
   void render(Canvas canvas) {
+    final panRect = this.panRect;
     super.render(canvas);
-    _taps.values.forEach((rect) {
+    taps.values.forEach((rect) {
-      canvas.drawRect(rect, _whitePaint);
+      canvas.drawRect(rect, whitePaint);
     });
 
-    if (_panRect != null) {
+    if (panRect != null) {
-      canvas.drawRect(_panRect, _whitePaint);
+      canvas.drawRect(panRect, whitePaint);
     }
   }
 }

examples/lib/stories/controls/overlapping_tapables.dart

@@ -19,13 +19,12 @@ class TapableSquare extends PositionComponent with Tapable {
 
   Paint currentPaint;
 
-  TapableSquare({Vector2 position})
+  TapableSquare({Vector2? position})
-      : super(
+      : currentPaint = _randomPaint(),
+        super(
           position: position ?? Vector2.all(100),
           size: Vector2.all(100),
-        ) {
+        );
-    currentPaint = _randomPaint();
-  }
 
   @override
   void render(Canvas canvas) {

examples/lib/stories/controls/scroll.dart

@@ -12,7 +12,7 @@ class ScrollGame extends BaseGame with ScrollDetector {
   final _paint = BasicPalette.white.paint;
 
   Vector2 position = Vector2.all(100);
-  Vector2 target;
+  Vector2? target;
 
   @override
   void onScroll(PointerScrollEvent event) {
@@ -29,6 +29,7 @@ class ScrollGame extends BaseGame with ScrollDetector {
   @override
   void update(double dt) {
     super.update(dt);
+    final target = this.target;
     if (target != null) {
       final dir = (target - position).normalized();
       position += dir * (speed * dt);

examples/lib/stories/controls/tapables.dart

@@ -9,7 +9,7 @@ class TapableSquare extends PositionComponent with Tapable {
 
   bool _beenPressed = false;
 
-  TapableSquare({Vector2 position})
+  TapableSquare({Vector2? position})
       : super(
           position: position ?? Vector2.all(100),
           size: Vector2.all(100),

examples/lib/stories/effects/combined_effect.dart

@@ -10,7 +10,7 @@ final green = Paint()..color = const Color(0xAA338833);
 final red = Paint()..color = const Color(0xAA883333);
 
 class CombinedEffectGame extends BaseGame with TapDetector {
-  SquareComponent greenSquare, redSquare;
+  late SquareComponent greenSquare, redSquare;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/effects/infinite_effect.dart

@@ -19,9 +19,9 @@ SquareComponent makeSquare(Paint paint) {
 }
 
 class InfiniteEffectGame extends BaseGame with TapDetector {
-  SquareComponent greenSquare;
+  late SquareComponent greenSquare;
-  SquareComponent redSquare;
+  late SquareComponent redSquare;
-  SquareComponent orangeSquare;
+  late SquareComponent orangeSquare;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/effects/move_effect.dart

@@ -7,7 +7,7 @@ import 'package:flutter/material.dart';
 import '../../commons/square_component.dart';
 
 class MoveEffectGame extends BaseGame with TapDetector {
-  SquareComponent square;
+  late SquareComponent square;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/effects/rotate_effect.dart

@@ -10,7 +10,7 @@ import 'package:flutter/material.dart';
 import '../../commons/square_component.dart';
 
 class RotateEffectGame extends BaseGame with TapDetector {
-  SquareComponent square;
+  late SquareComponent square;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/effects/scale_effect.dart

@@ -8,7 +8,7 @@ import 'package:flutter/material.dart';
 import '../../commons/square_component.dart';
 
 class ScaleEffectGame extends BaseGame with TapDetector {
-  SquareComponent square;
+  late SquareComponent square;
   bool grow = true;
 
   @override

examples/lib/stories/effects/sequence_effect.dart

@@ -9,7 +9,7 @@ import '../../commons/square_component.dart';
 final green = Paint()..color = const Color(0xAA338833);
 
 class SequenceEffectGame extends BaseGame with TapDetector {
-  SquareComponent greenSquare;
+  late SquareComponent greenSquare;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/parallax/component.dart

@@ -13,7 +13,7 @@ class MyParallaxComponent extends ParallaxComponent
     with HasGameRef<ComponentParallaxGame> {
   @override
   Future<void> onLoad() async {
-    parallax = await gameRef.loadParallax(
+    parallax = await gameRef!.loadParallax(
       [
         'parallax/bg.png',
         'parallax/mountain-far.png',

examples/lib/stories/parallax/no_fcs.dart

@@ -10,7 +10,7 @@ import 'package:flutter/material.dart';
 /// FCS is only used when you extend BaseGame, not Game,
 /// like we do in this example.
 class NoFCSParallaxGame extends Game {
-  Parallax parallax;
+  late Parallax parallax;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/rendering/layers.dart

@@ -45,8 +45,8 @@ class BackgroundLayer extends PreRenderedLayer {
 }
 
 class LayerGame extends Game {
-  Layer gameLayer;
+  late Layer gameLayer;
-  Layer backgroundLayer;
+  late Layer backgroundLayer;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/rendering/text.dart

@@ -5,8 +5,8 @@ import 'package:flame/game.dart';
 import 'package:flame/palette.dart';
 import 'package:flutter/material.dart';
 
-final regular = TextConfig(color: BasicPalette.white.color);
+final _regular = TextConfig(color: BasicPalette.white.color);
-final tiny = regular.withFontSize(12.0);
+final _tiny = _regular.withFontSize(12.0);
 
 final _white = Paint()
   ..color = BasicPalette.white.color
@@ -16,7 +16,7 @@ class MyTextBox extends TextBoxComponent {
   MyTextBox(String text)
       : super(
           text,
-          config: tiny,
+          config: _tiny,
           boxConfig: TextBoxConfig(
             timePerChar: 0.05,
             growingBox: true,
@@ -43,20 +43,20 @@ class TextGame extends BaseGame {
   @override
   Future<void> onLoad() async {
     add(
-      TextComponent('Hello, Flame', config: regular)
+      TextComponent('Hello, Flame', config: _regular)
         ..anchor = Anchor.topCenter
         ..x = size.x / 2
         ..y = 32.0,
     );
 
     add(
-      TextComponent('center', config: tiny)
+      TextComponent('center', config: _tiny)
         ..anchor = Anchor.center
         ..position = size / 2,
     );
 
     add(
-      TextComponent('bottomRight', config: tiny)
+      TextComponent('bottomRight', config: _tiny)
         ..anchor = Anchor.bottomRight
         ..position = size,
     );

examples/lib/stories/sprites/spritebatch_auto_load.dart

@@ -9,7 +9,8 @@ class MySpriteBatchComponent extends SpriteBatchComponent
     with HasGameRef<SpritebatchAutoLoadGame> {
   @override
   Future<void> onLoad() async {
-    spriteBatch = await gameRef.loadSpriteBatch('boom.png');
+    final spriteBatch = await gameRef!.loadSpriteBatch('boom.png');
+    this.spriteBatch = spriteBatch;
 
     spriteBatch.add(
       source: const Rect.fromLTWH(128 * 4.0, 128 * 4.0, 64, 128),
@@ -25,14 +26,14 @@ class MySpriteBatchComponent extends SpriteBatchComponent
       color: Colors.redAccent,
     );
 
+    final size = gameRef!.size;
     const num = 100;
     final r = Random();
     for (var i = 0; i < num; ++i) {
       final sx = r.nextInt(8) * 128.0;
       final sy = r.nextInt(8) * 128.0;
-      final x = r.nextInt(gameRef.size.x.toInt()).toDouble();
+      final x = r.nextInt(size.x.toInt()).toDouble();
-      final y =
+      final y = r.nextInt(size.y ~/ 2).toDouble() + size.y / 2.0;
-          r.nextInt(gameRef.size.y ~/ 2).toDouble() + gameRef.size.y / 2.0;
       spriteBatch.add(
         source: Rect.fromLTWH(sx, sy, 128, 128),
         offset: Vector2(x - 64, y - 64),

examples/lib/stories/tile_maps/isometric_tile_map.dart

@@ -34,8 +34,8 @@ class Selector extends SpriteComponent {
 }
 
 class IsometricTileMapGame extends BaseGame with MouseMovementDetector {
-  IsometricTileMapComponent base;
+  late IsometricTileMapComponent base;
-  Selector selector;
+  late Selector selector;
 
   IsometricTileMapGame();
 
@@ -73,9 +73,6 @@ class IsometricTileMapGame extends BaseGame with MouseMovementDetector {
 
   @override
   void onMouseMove(PointerHoverEvent event) {
-    if (base == null || selector == null) {
-      return; // loading
-    }
     final screenPosition = event.localPosition.toVector2();
     final block = base.getBlock(screenPosition);
     selector.show = base.containsBlock(block);

examples/lib/stories/utils/camera_and_viewport.dart

@@ -17,14 +17,14 @@ class MovableSquare extends SquareComponent
   static final TextConfig config = TextConfig(fontSize: 12);
 
   final Vector2 velocity = Vector2.zero();
-  Timer timer;
+  late Timer timer;
 
   MovableSquare() {
     addShape(HitboxRectangle());
     timer = Timer(3.0)
       ..stop()
       ..callback = () {
-        gameRef.camera.setRelativeOffset(Anchor.center.toVector2());
+        gameRef!.camera.setRelativeOffset(Anchor.center.toVector2());
       };
   }
 
@@ -50,7 +50,7 @@ class MovableSquare extends SquareComponent
   @override
   void onCollision(Set<Vector2> points, Collidable other) {
     if (other is Rock) {
-      gameRef.camera.setRelativeOffset(Anchor.topCenter.toVector2());
+      gameRef!.camera.setRelativeOffset(Anchor.topCenter.toVector2());
       timer.start();
     }
   }
@@ -95,7 +95,7 @@ class Rock extends SquareComponent with Hitbox, Collidable {
 
 class CameraAndViewportGame extends BaseGame
     with KeyboardEvents, HasCollidables {
-  MovableSquare square;
+  late MovableSquare square;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/utils/nine_tile_box.dart

@@ -3,7 +3,7 @@ import 'package:flame/game.dart';
 import 'package:flutter/material.dart';
 
 class NineTileBoxGame extends Game {
-  NineTileBox nineTileBox;
+  late NineTileBox nineTileBox;
 
   @override
   Future<void> onLoad() async {

examples/lib/stories/utils/particles.dart

@@ -28,17 +28,14 @@ class ParticlesGame extends BaseGame {
   /// Defines the lifespan of all the particles in these examples
   final sceneDuration = const Duration(seconds: 1);
 
-  Vector2 cellSize;
+  Vector2 get cellSize => size / gridSize;
-  Vector2 halfCellSize;
+  Vector2 get halfCellSize => cellSize / 2;
 
   @override
   Future<void> onLoad() async {
     await images.load('zap.png');
     await images.load('boom.png');
 
-    cellSize = size / gridSize;
-    halfCellSize = cellSize * .5;
-
     // Spawn new particles every second
     Timer.periodic(sceneDuration, (_) => spawnParticles());
   }
@@ -78,8 +75,7 @@ class ParticlesGame extends BaseGame {
       final particle = particles.removeLast();
       final col = particles.length % gridSize;
       final row = (particles.length ~/ gridSize).toDouble();
-      final cellCenter =
+      final cellCenter = (cellSize..multiply(Vector2(col, row))) + halfCellSize;
-          (cellSize.clone()..multiply(Vector2(col, row))) + (cellSize * .5);
 
       add(
         // Bind all the particles to a [Component] update
@@ -218,7 +214,7 @@ class ParticlesGame extends BaseGame {
             Colors.red,
             Colors.blue,
             particle.progress,
-          ),
+          )!,
       ),
     );
   }
@@ -242,14 +238,14 @@ class ParticlesGame extends BaseGame {
               Colors.red,
               Colors.blue,
               steppedProgress,
-            ),
+            )!,
         );
       },
     );
   }
 
   /// Particle which is used in example below
-  Particle reusablePatricle;
+  Particle? reusablePatricle;
 
   /// A burst of white circles which actually using a single circle
   /// as a form of optimization. Look for reusing parts of particle effects
@@ -261,7 +257,7 @@ class ParticlesGame extends BaseGame {
       generator: (i) => MovingParticle(
         curve: Interval(rnd.nextDouble() * .1, rnd.nextDouble() * .8 + .1),
         to: randomCellOffset() * .5,
-        child: reusablePatricle,
+        child: reusablePatricle!,
       ),
     );
   }
@@ -277,7 +273,7 @@ class ParticlesGame extends BaseGame {
   }
 
   /// Particle which is used in example below
-  Particle reusableImageParticle;
+  Particle? reusableImageParticle;
 
   /// A single [imageParticle] is drawn 9 times
   /// in a grid within grid cell. Looks as 9 particles
@@ -298,7 +294,7 @@ class ParticlesGame extends BaseGame {
           (i % perLine) * colWidth - halfCellSize.x + imageSize,
           (i ~/ perLine) * rowHeight - halfCellSize.y + imageSize,
         ),
-        child: reusableImageParticle,
+        child: reusableImageParticle!,
       ),
     );
   }

examples/lib/stories/utils/timer.dart

@@ -5,12 +5,13 @@ import 'package:flame/gestures.dart';
 
 class TimerGame extends Game with TapDetector {
   final TextConfig textConfig = TextConfig(color: const Color(0xFFFFFFFF));
-  Timer countdown;
+  late Timer countdown;
-  Timer interval;
+  late Timer interval;
 
   int elapsedSecs = 0;
 
-  TimerGame() {
+  @override
+  Future<void> onLoad() async {
     countdown = Timer(2);
     interval = Timer(
       1,

examples/lib/stories/widgets/overlay.dart

@@ -9,14 +9,14 @@ Widget overlayBuilder(DashbookContext ctx) {
 }
 
 class OverlayExampleWidget extends StatefulWidget {
-  const OverlayExampleWidget({Key key}) : super(key: key);
+  const OverlayExampleWidget({Key? key}) : super(key: key);
 
   @override
   _OverlayExampleWidgetState createState() => _OverlayExampleWidgetState();
 }
 
 class _OverlayExampleWidgetState extends State<OverlayExampleWidget> {
-  ExampleGame _myGame;
+  ExampleGame? _myGame;
 
   Widget pauseMenuBuilder(BuildContext buildContext, ExampleGame game) {
     return Center(
@@ -33,14 +33,15 @@ class _OverlayExampleWidgetState extends State<OverlayExampleWidget> {
 
   @override
   Widget build(BuildContext context) {
+    final myGame = _myGame;
     return Scaffold(
       appBar: AppBar(
         title: const Text('Testing addingOverlay'),
       ),
-      body: _myGame == null
+      body: myGame == null
           ? const Text('Wait')
           : GameWidget<ExampleGame>(
-              game: _myGame,
+              game: myGame,
               overlayBuilderMap: {
                 'PauseMenu': pauseMenuBuilder,
               },

examples/lib/stories/widgets/sprite_animation_widget.dart

@@ -24,7 +24,7 @@ Widget spriteAnimationWidgetBuilder(DashbookContext ctx) {
       animation: _animation,
       playing: ctx.boolProperty('playing', true),
       anchor: Anchor.valueOf(
-        ctx.listProperty('anchor', 'Anchor.center', anchorOptions),
+        ctx.listProperty('anchor', 'center', anchorOptions),
       ),
     ),
   );

examples/lib/stories/widgets/sprite_widget.dart

@@ -12,7 +12,7 @@ Widget spriteWidgetBuilder(DashbookContext ctx) {
     child: SpriteWidget(
       sprite: Sprite(Flame.images.fromCache('shield.png')),
       anchor: Anchor.valueOf(
-        ctx.listProperty('anchor', 'Anchor.center', anchorOptions),
+        ctx.listProperty('anchor', 'center', anchorOptions),
       ),
     ),
   );

examples/pubspec.yaml

@@ -5,12 +5,13 @@ publish_to: 'none'
 version: 0.1.0
 
 environment:
-  sdk: ">=2.10.0 <3.0.0"
+  sdk: ">=2.12.0-29.10.beta <3.0.0"
+  flutter: ">=1.24.0-10.2.pre"
 
 dependencies:
   flame:
     path: ../packages/flame
-  dashbook: 0.0.12
+  dashbook: 0.1.0
   flutter:
     sdk: flutter
 

packages/flame/lib/src/anchor.dart

@@ -97,7 +97,10 @@ class Anchor {
     } else {
       final regexp = RegExp(r'^\Anchor\(([^,]+), ([^\)]+)\)');
       final matches = regexp.firstMatch(name)?.groups([1, 2]);
-      assert(matches != null && matches.length == 2, 'Bad anchor format');
+      assert(
+        matches != null && matches.length == 2,
+        'Bad anchor format: $name',
+      );
       return Anchor(double.parse(matches![0]!), double.parse(matches[1]!));
     }
   }