books

assets/draw/p06/s05.dart

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+
+import 'dart:ui';
+
+import 'package:flutter/material.dart';
+
+import '../components/coordinate.dart';
+
+
+
+/// create by 张风捷特烈 on 2020/5/1
+/// 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,
+      child: CustomPaint(
+        // 使用CustomPaint
+        painter: PaperPainter(),
+      ),
+    );
+  }
+
+}
+
+class PaperPainter extends CustomPainter {
+  final Coordinate coordinate = Coordinate();
+
+
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    coordinate.paint(canvas, 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();
+    pms.forEach((pm) {
+      print(
+          "---length:-${pm.length}----contourIndex:-${pm.contourIndex}----contourIndex:-${pm.isClosed}----");
+
+      Tangent? tangent = pm.getTangentForOffset(pm.length * 0.5);
+      if(tangent==null) return;
+      print(
+          "---position:-${tangent.position}----angle:-${tangent.angle}----vector:-${tangent.vector}----");
+
+      canvas.drawCircle(
+          tangent.position, 5, Paint()..color = Colors.deepOrange);
+    });
+
+    canvas.drawPath(path, paint);
+  }
+
+  @override
+  bool shouldRepaint(CustomPainter oldDelegate) => false;
+}