Creating Particles with Flutter and GraphX #short

main.dart

/// roipeker 2023.
/// 
/// #short tutorial: https://youtu.be/I8Yo9jq4hXs
///

import 'package:flutter/material.dart';
import 'package:graphx/graphx.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  final onCounterChanged = ValueNotifier(0);

  void _incrementCounter() {
    setState(() {
      _counter++;
      onCounterChanged.value = _counter;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
          ],
        ),
      ),
      floatingActionButton: SceneBuilderWidget(
        builder: () => SceneController(back: ParticlesScene(onCounterChanged)),
        child: FloatingActionButton(
          onPressed: _incrementCounter,
          tooltip: 'Increment',
          child: const Icon(Icons.add),
        ),
      ),
    );
  }
}

class ParticlesScene extends GSprite {
  final ValueNotifier onCounterChanged;

  ParticlesScene(this.onCounterChanged);

  @override
  void dispose() {
    onCounterChanged.removeListener(_onCounterChanged);
    super.dispose();
  }

  late GSimpleParticleSystem particles;

  void _onCounterChanged() {
    particles.forceBurst();
  }

  @override
  void addedToStage() {
    onCounterChanged.addListener(_onCounterChanged);

    particles = GSimpleParticleSystem();
    particles.emit = false;
    particles.texture = GIcon(Icons.favorite, Colors.white, 32).createImageTextureSync();

    addChild(particles);
    particles.initialColor = Colors.pink.value;
    particles.endColor = Colors.yellow.value;
    particles.x = stage!.stageWidth / 2;
    particles.y = stage!.stageHeight / 2;
    particles.dispersionAngle = Math.PI;
    particles.dispersionAngleVariance = Math.PI / 2;

    particles.initialVelocity = 100;
    particles.initialVelocityVariance = 100;

    particles.initialAcceleration = .15;
    particles.initialAccelerationVariance = .15;

    particles.emission = 20;
    particles.endScale = 0.2;
    particles.endScaleVariance = 0.2;
    particles.initialAngularVelocity = -.003;
    particles.initialAngularVelocityVariance = .006;
    particles.initialAngleVariance = Math.PI / 2;
    particles.initialScale = .4;
    particles.initialScaleVariance = .8;
    particles.endAlpha = 0;
    particles.endAlphaVariance = .3;
    particles.blendMode = BlendMode.difference;
  }
}