type 'List<Comparable<dynamic>>' is not a subtype of type 'Iterable<Pair>' of 'iterable'

[spkingr]

When I make a simple game, I got the error again and again, how to solve it, thanks!

Another exception was thrown: type 'List<Comparable<dynamic>>' is not a subtype of type 'Iterable<Pair>' of 'iterable'

And the stack:

I/flutter (20726): When the exception was thrown, this was the stack:
I/flutter (20726): #0      List.setRange (dart:core/runtime/libarray.dart)
I/flutter (20726): #1      sort (package:box2d/src/buffer_utils.dart:151:8)
I/flutter (20726): #2      DefaultBroadPhaseBuffer.updatePairs (file:///D:/Software/Google/Flutter/SDK/flutter/.pub-cache/hosted/pub.flutter-io.cn/box2d-0.4.0/lib/src/collision/broadphase/default_broadphase_buffer.dart:140:17)
I/flutter (20726): #3      ContactManager.findNewContacts (file:///D:/Software/Google/Flutter/SDK/flutter/.pub-cache/hosted/pub.flutter-io.cn/box2d-0.4.0/lib/src/dynamics/contact_manager.dart:165:16)
I/flutter (20726): #4      World.stepDt (file:///D:/Software/Google/Flutter/SDK/flutter/.pub-cache/hosted/pub.flutter-io.cn/box2d-0.4.0/lib/src/dynamics/world.dart:566:23)
I/flutter (20726): #5      Box2DComponent.update (package:project_simple_game/flame/box2d/box2d_component.dart:39:11)
I/flutter (20726): #6      GameWorld.update (package:project_simple_game/game_world.dart:26:11)
I/flutter (20726): #7      GameRoot.update (package:project_simple_game/game_root.dart:33:21)
I/flutter (20726): #8      _GameRenderBox._update (package:project_simple_game/flame/game.dart:119:10)
I/flutter (20726): #9      _GameRenderBox._tick (package:project_simple_game/flame/game.dart:112:5)
I/flutter (20726): #10     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter (20726): #11     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleBeginFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:906:11)
I/flutter (20726): #12     __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.forEach (dart:collection/runtime/libcompact_hash.dart:363:8)
I/flutter (20726): #13     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleBeginFrame (package:flutter/src/scheduler/binding.dart:904:17)
I/flutter (20726): #14     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:747:7)
I/flutter (20726): #16     _Timer._runTimers (dart:isolate/runtime/libtimer_impl.dart:382:19)
I/flutter (20726): #17     _Timer._handleMessage (dart:isolate/runtime/libtimer_impl.dart:416:5)
I/flutter (20726): #18     _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)
I/flutter (20726): (elided one frame from package dart:async)
I/flutter (20726): 
I/flutter (20726): 
I/flutter (20726): This exception was thrown in the context of a scheduler callback. When the scheduler callback was
I/flutter (20726): _registered_ (as opposed to when the exception was thrown), this was the stack:
I/flutter (20726): #0      new _FrameCallbackEntry.<anonymous closure> (package:flutter/src/scheduler/binding.dart:109:33)
I/flutter (20726): #1      new _FrameCallbackEntry (package:flutter/src/scheduler/binding.dart:112:6)
I/flutter (20726): #2      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleFrameCallback (package:flutter/src/scheduler/binding.dart:426:53)
I/flutter (20726): #3      _GameRenderBox._scheduleTick (package:project_simple_game/flame/game.dart:102:50)
I/flutter (20726): #4      _GameRenderBox._tick (package:project_simple_game/flame/game.dart:111:5)
I/flutter (20726): #5      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter (20726): #6      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleBeginFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:906:11)
I/flutter (20726): #7      __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.forEach (dart:collection/runtime/libcompact_hash.dart:363:8)
I/flutter (20726): #8      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleBeginFrame (package:flutter/src/scheduler/binding.dart:904:17)
I/flutter (20726): #9      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleBeginFrame (package:flutter/src/scheduler/binding.dart:834:5)
I/flutter (20726): #10     _invoke1 (dart:ui/hooks.dart:134:13)
I/flutter (20726): #11     _beginFrame (dart:ui/hooks.dart:105:3)

[luanpotter]

Could you please provide your code relevant to the error? I can only guess that you created a world (Box2DComponent) and added inside Components that are not bodies (BodyComponent). All components added directly inside a Box2DComponent must be BodyComponents.

[spkingr]

Here is my test code:

class GameRoot extends Game{
  GameRoot(){
    this._gameWorld = GameWorld();
    this._gameWorld.initializeWorld();
    this._initAssets().then((_) => this._isLoaded = true);
  }

  GameWorld _gameWorld;
  bool _isLoaded = false;
  Size _dimensions;

  Future<Null> _initAssets() async{
    this._dimensions = await Flame.util.initialDimensions();
    await Flame.audio.load('supersoyboy.ogg');
    await Flame.audio.load('dryfire.mp3');
    Flame.audio.loop('supersoyboy.ogg');
  }

  @override
  void render(Canvas canvas) {
    this._gameWorld.render(canvas);
  }

  @override
  void update(double t){
    this._gameWorld.update(t);
  }

  @override
  void resize(Size size){
    this._gameWorld.resize(size);
  }
}

And another file:

class GameWorld extends Box2DComponent{
  GameWorld():super();

  SuperBoyComponent player;

  @override
  void initializeWorld() {
    //this.add(BackgroundComponent(this.viewport));
    //this.add(GroundComponent(this));
    this.player = SuperBoyComponent(this);
    this.add(this.player);
  }

  @override
  void update(double t) {
    try{
      super.update(t); //This line triggers the error!
    }catch(e){
      print("Error:------------------$e");
    }
    this.cameraFollow(this.player, horizontal: 0.5);
  }
}

class SuperBoyComponent extends BodyComponent{
  static final double playerHeight = 48.0;
  static final double playerWidth = 40.0;

  SuperBoyComponent(Box2DComponent box) : super(box){
    this._loadImages().then((_) => this._isLoading = false);
    this._createBody();
  }

  bool _isLoading = true;
  final images = Map<String, Image>();

  bool _isIdle = true;
  bool _isRun = false;
  bool _isJump = false;
  bool _isSlide = false;

  @override
  void update(double t) {
    this._isIdle = this.body.linearVelocity.x == 0.0;
    this._isRun = this.body.linearVelocity.x != 0.0;
    this._isJump = this.body.getContactList() == null;
  }

  @override
  void renderPolygon(Canvas canvas, List<Offset> points){
    if(this._isLoading){
      return;
    }

    Image image = this._isJump ? this.images["jump_1"] : (this._isIdle ? this.images["run_1"] : (this._isRun ? this.images["run_1"] : this.images["slide_1"]));
    final rect = Rect.fromLTWH(- SuperBoyComponent.playerWidth * 0.5, - SuperBoyComponent.playerHeight * 0.5, SuperBoyComponent.playerWidth, SuperBoyComponent.playerHeight);
    paintImage(canvas: canvas, image: image, rect: rect, fit: BoxFit.contain, flipHorizontally: this.body.linearVelocity.x < 0.0);
  }

  Future<Null> _loadImages() async{
    /// run_1 run_15
    /// jump_1 jump 15
    /// slide_1
    Image image;
    for(int i = 1; i <= 15; i ++){
      image = await Flame.images.load("run_$i.png");
      this.images["run_$i"] = image;
      image = await Flame.images.load("jump_$i.png");
      this.images["jump_$i"] = image;
    }
    image = await Flame.images.load("slide_1.png");
    this.images["slide_1"] = image;
  }

  void _createBody(){
    final shape = PolygonShape()
      ..setAsBoxXY(SuperBoyComponent.playerWidth, SuperBoyComponent.playerHeight);
    shape.centroid.x = SuperBoyComponent.playerWidth * 0.5;
    shape.centroid.y = SuperBoyComponent.playerHeight * 0.5;

    final fixtureDef = FixtureDef()
      ..shape = shape
      ..restitution = 0.0
      ..density = 0.05
      ..friction = 0.2;

    final bodyDef = BodyDef()
      ..linearVelocity = Vector2.zero()
      ..position = Vector2(0.0, 15.0)
      ..bullet = true
      ..type = BodyType.DYNAMIC;

    this.body = this.world.createBody(bodyDef)
      ..createFixtureFromFixtureDef(fixtureDef)
      ..setFixedRotation(true);
  }
}

Thanks very much for help!

[feroult]

Hi @spkingr, thanks for your code.
I was able reproduce the problem and I'm trying to fix it.

[feroult]

It was a bug in Box2D Dart port. Since the original maintainer was not merging this PR from Feb, we decided to fork the project and create our own package.

You'll need to change any references to box2d package or sub-packages to add the _flame suffix:

import 'package:box2d_flame/box2d.dart';

Just wait @luanpotter to release next Flame version and you should be ok with your code.

Best

[luanpotter]

@spkingr the new version was released (0.9.1). Could you verify if the problem is solved? Thanks!

[spkingr]

It works now! Happy to go on flutter game. :) @luanpotter @feroult