flame/doc/tutorials/space_shooter/app/lib/step5/main.dart

import 'package:flame/components.dart';
import 'package:flame/events.dart';
import 'package:flame/experimental.dart';
import 'package:flame/game.dart';
import 'package:flame/input.dart';
import 'package:flame/parallax.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(GameWidget(game: SpaceShooterGame()));
}

class SpaceShooterGame extends FlameGame with PanDetector {
  late Player player;

  @override
  Future<void> onLoad() async {
    final parallax = await loadParallaxComponent(
      [
        ParallaxImageData('stars_0.png'),
        ParallaxImageData('stars_1.png'),
        ParallaxImageData('stars_2.png'),
      ],
      baseVelocity: Vector2(0, -5),
      repeat: ImageRepeat.repeat,
      velocityMultiplierDelta: Vector2(0, 5),
    );
    add(parallax);

    player = Player();
    add(player);

    add(
      SpawnComponent(
        factory: (index) {
          return Enemy();
        },
        period: 1,
        area: Rectangle.fromLTWH(0, 0, size.x, -Enemy.enemySize),
      ),
    );
  }

  @override
  void onPanUpdate(DragUpdateInfo info) {
    player.move(info.delta.global);
  }

  @override
  void onPanStart(DragStartInfo info) {
    player.startShooting();
  }

  @override
  void onPanEnd(DragEndInfo info) {
    player.stopShooting();
  }
}

class Player extends SpriteAnimationComponent
    with HasGameReference<SpaceShooterGame> {
  Player()
      : super(
          size: Vector2(100, 150),
          anchor: Anchor.center,
        );

  late final SpawnComponent _bulletSpawner;

  @override
  Future<void> onLoad() async {
    await super.onLoad();

    animation = await game.loadSpriteAnimation(
      'player.png',
      SpriteAnimationData.sequenced(
        amount: 4,
        stepTime: 0.2,
        textureSize: Vector2(32, 48),
      ),
    );

    position = game.size / 2;

    _bulletSpawner = SpawnComponent(
      period: 0.2,
      selfPositioning: true,
      factory: (index) {
        return Bullet(
          position: position +
              Vector2(
                0,
                -height / 2,
              ),
        );
      },
      autoStart: false,
    );

    game.add(_bulletSpawner);
  }

  void move(Vector2 delta) {
    position.add(delta);
  }

  void startShooting() {
    _bulletSpawner.timer.start();
  }

  void stopShooting() {
    _bulletSpawner.timer.stop();
  }
}

class Bullet extends SpriteAnimationComponent
    with HasGameReference<SpaceShooterGame> {
  Bullet({
    super.position,
  }) : super(
          size: Vector2(25, 50),
          anchor: Anchor.center,
        );

  @override
  Future<void> onLoad() async {
    await super.onLoad();

    animation = await game.loadSpriteAnimation(
      'bullet.png',
      SpriteAnimationData.sequenced(
        amount: 4,
        stepTime: 0.2,
        textureSize: Vector2(8, 16),
      ),
    );
  }

  @override
  void update(double dt) {
    super.update(dt);

    position.y += dt * -500;

    if (position.y < -height) {
      removeFromParent();
    }
  }
}

class Enemy extends SpriteAnimationComponent
    with HasGameReference<SpaceShooterGame> {
  Enemy({
    super.position,
  }) : super(
          size: Vector2.all(enemySize),
          anchor: Anchor.center,
        );

  static const enemySize = 50.0;

  @override
  Future<void> onLoad() async {
    await super.onLoad();

    animation = await game.loadSpriteAnimation(
      'enemy.png',
      SpriteAnimationData.sequenced(
        amount: 4,
        stepTime: 0.2,
        textureSize: Vector2.all(16),
      ),
    );
  }

  @override
  void update(double dt) {
    super.update(dt);

    position.y += dt * 250;

    if (position.y > game.size.y) {
      removeFromParent();
    }
  }
}