books

assets/draw/p10/s05.dart

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+import 'dart:math';
+
+import 'package:flutter/material.dart';
+
+/// create by 张风捷特烈 on 2020/11/2
+/// contact me by email 1981462002@qq.com
+/// 说明:
+///
+
+class Paper extends StatefulWidget {
+  final Color color;
+
+  const Paper({Key? key, this.color = Colors.lightBlue}) : super(key: key);
+
+  @override
+  _PaperState createState() => _PaperState();
+}
+
+class _PaperState extends State<Paper> with SingleTickerProviderStateMixin {
+  late AnimationController _controller;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = AnimationController(
+      duration: const Duration(seconds: 1),
+      vsync: this,
+    );
+
+    _controller.repeat(reverse: true);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      child: CustomPaint(
+        size: Size(100, 100), painter: PicManPainter(_controller), // 背景
+      ),
+    );
+  }
+}
+
+class PicManPainter extends CustomPainter {
+  final Animation<double> repaint;
+
+  // 创建 Tween
+  final ColorDoubleTween tween = ColorDoubleTween(
+      begin: ColorDouble(color: Colors.blue, value: 10),
+      end: ColorDouble(color: Colors.red, value: 10));
+
+  Paint _paint = Paint();
+
+  PicManPainter(this.repaint) : super(repaint: repaint);
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    canvas.clipRect(Offset.zero & size); //剪切画布
+    final double radius = size.width / 2;
+    canvas.translate(radius, size.height / 2);
+    _drawHead(canvas, size);
+    _drawEye(canvas, radius);
+  }
+
+  //绘制头
+  void _drawHead(Canvas canvas, Size size) {
+    var rect = Rect.fromCenter(
+        center: Offset(0, 0), height: size.width, width: size.height);
+    var a = tween.evaluate(repaint).value / 180 * pi;
+    canvas.drawArc(rect, a, 2 * pi - a.abs() * 2, true,
+        _paint..color = tween.evaluate(repaint).color ?? Colors.black);
+  }
+
+  //绘制眼睛
+  void _drawEye(Canvas canvas, double radius) {
+    canvas.drawCircle(Offset(radius * 0.15, -radius * 0.6), radius * 0.12,
+        _paint..color = Colors.white);
+  }
+
+  @override
+  bool shouldRepaint(covariant PicManPainter oldDelegate) =>
+      oldDelegate.repaint != repaint;
+}
+
+class ColorDouble {
+  final Color? color;
+  final double value;
+
+  ColorDouble({this.color = Colors.blue, this.value = 0});
+}
+
+class ColorDoubleTween extends Tween<ColorDouble> {
+  ColorDoubleTween({required ColorDouble begin, required ColorDouble end})
+      : super(begin: begin, end: end);
+
+  @override
+  ColorDouble lerp(double t) => ColorDouble(
+        color: Color.lerp(begin?.color, end?.color, t),
+        value: (begin!.value + (end!.value - begin!.value) * t),
+      );
+}