books

packages/idraw/lib/p18/s01.dart

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+import 'dart:math';
+
+// import 'dart:ui' as ui;
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+
+/// create by 张风捷特烈 on 2020/11/5
+/// contact me by email 1981462002@qq.com
+/// 说明:
+
+class Paper extends StatelessWidget {
+  const Paper({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      color: Colors.white,
+      alignment: Alignment.center,
+      child: const World(),
+    );
+  }
+}
+
+class World extends StatefulWidget {
+  const World({super.key});
+
+  @override
+  _WorldState createState() => _WorldState();
+}
+
+class _WorldState extends State<World> with SingleTickerProviderStateMixin {
+  late AnimationController _controller;
+  ParticleManage pm = ParticleManage();
+
+  @override
+  void initState() {
+    super.initState();
+    initParticleManage();
+
+    _controller = AnimationController(
+      duration: const Duration(seconds: 1),
+      vsync: this,
+    )
+      ..addListener(pm.tick)
+    // ..repeat()
+        ;
+  }
+
+  void initParticleManage() {
+    pm.size = Size(300, 200);
+    Particle particle = Particle(x: 0, y: 0, vx: 3, vy: 0,ay: 0.05,
+        color: Colors.blue, size: 8);
+    pm.particles = [particle];
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
+  theWorld(){
+    if (_controller.isAnimating) {
+      _controller.stop();
+    } else {
+      _controller.repeat();
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      onTap: theWorld,
+      child: CustomPaint(
+        size: pm.size,
+        painter: WorldRender(manage: pm),
+      ),
+    );
+  }
+}
+
+class ParticleManage with ChangeNotifier {
+  List<Particle> particles = [];
+
+  Size size;
+
+  ParticleManage({this.size = Size.zero});
+
+  void setParticles(List<Particle> particles) {
+    this.particles = particles;
+  }
+
+  void addParticle(Particle particle) {
+    particles.add(particle);
+    notifyListeners();
+  }
+
+  void tick() {
+    particles.forEach(doUpdate);
+    notifyListeners();
+  }
+
+  void doUpdate(Particle p) {
+    p.vy += p.ay; // y加速度变化
+    p.vx += p.ax; // x加速度变化
+    p.x += p.vx;
+    p.y += p.vy;
+    if (p.x > size.width) {
+      p.x = size.width;
+      p.vx = -p.vx;
+    }
+    if (p.x < 0) {
+      p.x = 0;
+      p.vx = -p.vx;
+    }
+    if (p.y > size.height) {
+      p.y = size.height;
+      p.vy = -p.vy;
+    }
+    if (p.y < 0) {
+      p.y = 0;
+      p.vy = -p.vy;
+    }
+  }
+
+  void reset() {
+    particles.forEach((p) {
+      p.x = 0;
+    });
+    notifyListeners();
+  }
+}
+
+class WorldRender extends CustomPainter {
+
+  final ParticleManage manage;
+
+  Paint fillPaint = Paint();
+
+  Paint stokePaint = Paint()
+    ..strokeWidth = 0.5
+    ..style = PaintingStyle.stroke;
+
+  WorldRender({required this.manage}) : super(repaint: manage);
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    canvas.drawRect(Offset.zero & size, stokePaint);
+    manage.particles.forEach((particle) {
+      drawParticle(canvas, particle);
+    });
+  }
+
+  void drawParticle(Canvas canvas, Particle particle) {
+    fillPaint.color = particle.color;
+    canvas.drawCircle(Offset(particle.x, particle.y), particle.size, fillPaint);
+  }
+
+  @override
+  bool shouldRepaint(covariant WorldRender oldDelegate) =>
+      oldDelegate.manage != manage;
+}
+
+
+class Particle {
+  /// x 位移.
+  double x;
+
+  /// y 位移.
+  double y;
+
+  /// 粒子水平速度.
+  double vx;
+
+  // 粒子水平加速度
+  double ax;
+
+  // 粒子竖直加速度
+  double ay;
+
+  ///粒子竖直速度.
+  double vy;
+
+
+  /// 粒子大小.
+  double size;
+
+  /// 粒子颜色.
+  Color color;
+
+  Particle({
+    this.x = 0,
+    this.y = 0,
+    this.ax = 0,
+    this.ay = 0,
+    this.vx = 0,
+    this.vy = 0,
+    this.size = 0,
+    this.color = Colors.black,
+  });
+}