books

assets/draw/p06/s06.dart

@@ -0,0 +1,83 @@
+import 'dart:ui';
+import 'package:flutter/material.dart';
+
+/// create by 张风捷特烈 on 2020/5/1
+/// contact me by email 1981462002@qq.com
+/// 说明:
+
+class Paper extends StatefulWidget {
+  const Paper({super.key});
+
+  @override
+  _PaperState createState() => _PaperState();
+}
+
+class _PaperState extends State<Paper> with SingleTickerProviderStateMixin {
+  late AnimationController _ctrl;
+  double progress = 0.0;
+
+  @override
+  void initState() {
+    super.initState();
+    _ctrl = AnimationController(
+        duration: Duration(seconds: 3), vsync: this)
+      ..forward();
+  }
+
+  @override
+  void dispose() {
+    _ctrl.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      color: Colors.white,
+      child: CustomPaint(
+        // 使用CustomPaint
+        painter: PaperPainter(progress: _ctrl),
+      ),
+    );
+  }
+}
+
+class PaperPainter extends CustomPainter {
+  final Animation<double> progress;
+
+  PaperPainter({required this.progress}) : super(repaint: progress);
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    canvas.translate(size.width / 2, size.height / 2);
+
+    Paint paint = Paint()
+      ..color = Colors.purple
+      ..strokeWidth = 1
+      ..style = PaintingStyle.stroke;
+
+    Path path = Path();
+    path
+      ..relativeMoveTo(0, 0)
+      ..relativeLineTo(-30, 120)
+      ..relativeLineTo(30, -30)
+      ..relativeLineTo(30, 30)
+      ..close();
+
+    path.addOval(Rect.fromCenter(center: Offset.zero, width: 50, height: 50));
+
+    PathMetrics pms = path.computeMetrics();
+    for (PathMetric pm in pms) {
+      Tangent? tangent = pm.getTangentForOffset(pm.length * progress.value);
+      if(tangent ==null) continue;
+      canvas.drawCircle(
+          tangent.position, 5, Paint()..color = Colors.deepOrange);
+    }
+
+    canvas.drawPath(path, paint);
+  }
+
+  @override
+  bool shouldRepaint(PaperPainter oldDelegate) =>
+      oldDelegate.progress != progress;
+}