flame/doc/examples/collision_detection/lib/main_simple.dart

import 'dart:ui';

import 'package:flame/components.dart';
import 'package:flame/extensions.dart';
import 'package:flame/flame.dart';
import 'package:flame/game.dart';
import 'package:flame/geometry.dart';
import 'package:flame/gestures.dart';
import 'package:flutter/material.dart' hide Image, Draggable;

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Flame.device.fullScreen();
  final game = MyGame();
  runApp(
    GameWidget(
      game: game,
    ),
  );
}

class MyCollidable extends PositionComponent
    with HasGameRef<MyGame>, Hitbox, Collidable {
  Vector2 velocity;
  final _collisionColor = Colors.amber;
  bool _isWallHit = false;
  bool _isCollision = false;

  MyCollidable(Vector2 position) {
    this.position = position;
    size = Vector2.all(100);
    anchor = Anchor.center;
    addShape(HitboxCircle());
  }

  @override
  Future<void> onLoad() async {
    final center = gameRef.size / 2;
    velocity = (center - position).normalized() * 150;
  }

  @override
  void update(double dt) {
    super.update(dt);
    if (_isWallHit) {
      remove();
      return;
    }
    debugColor = _isCollision ? _collisionColor : const Color(0xFFFF00FF);
    position.add(velocity * dt);
    _isCollision = false;
  }

  @override
  void render(Canvas canvas) {
    super.render(canvas);
    renderShapes(canvas);
  }

  @override
  void onCollision(Set<Vector2> intersectionPoints, Collidable other) {
    if (other is ScreenCollidable) {
      _isWallHit = true;
      return;
    }
    _isCollision = true;
  }
}

class MyGame extends BaseGame with HasCollidables, TapDetector {
  final TextConfig fpsTextConfig = TextConfig(
    color: const Color(0xFFFFFFFF),
  );

  @override
  Future<void> onLoad() async {
    add(ScreenCollidable());
  }

  @override
  void onTapDown(TapDownDetails details) {
    add(MyCollidable(details.localPosition.toVector2()));
  }
}