books

packages/idraw/lib/p14/s02.dart

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+import 'dart:ui';
+import 'package:flutter/material.dart';
+import '../components/coordinate_pro.dart';
+import 'touch_info.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> {
+  final TouchInfo touchInfo = TouchInfo();
+
+  @override
+  void dispose() {
+    touchInfo.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      onPanDown: _onPanDown,
+      onPanUpdate: _onPanUpdate,
+      child: Container(
+        color: Colors.white,
+        child: CustomPaint(
+          painter: PaperPainter(repaint: touchInfo),
+        ),
+      ),
+    );
+  }
+
+  void _onPanDown(DragDownDetails details) {
+    if (touchInfo.points.length < 3) {
+      touchInfo.addPoint(details.localPosition);
+    }else{
+      judgeZone(details.localPosition);
+    }
+  }
+
+
+  void _onPanUpdate(DragUpdateDetails details) {
+    judgeZone(details.localPosition,update: true);
+  }
+
+  ///判断出是否在某点的半径为r圆范围内
+  bool judgeCircleArea(Offset src, Offset dst, double r) =>
+      (src - dst).distance <= r;
+
+  //判断哪个点被选中
+  void judgeZone(Offset src,{bool update =false}) {
+    for (int i = 0; i < touchInfo.points.length; i++) {
+      if (judgeCircleArea(src, touchInfo.points[i], 15)) {
+        touchInfo.selectIndex = i;
+        if(update){
+          touchInfo.updatePoint(i, src);
+        }
+      }
+    }
+  }
+}
+
+class PaperPainter extends CustomPainter {
+  final Coordinate coordinate = Coordinate();
+
+  Paint _helpPaint = Paint()
+    ..color = Colors.purple
+    ..style = PaintingStyle.stroke
+    ..strokeCap = StrokeCap.round;
+
+  final TouchInfo repaint;
+
+  PaperPainter({ required this.repaint}) : super(repaint: repaint);
+  List<Offset> pos = [];
+
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    coordinate.paint(canvas, size);
+    canvas.translate(size.width / 2, size.height / 2);
+
+    pos = repaint.points
+        .map((e) => e.translate(-size.width / 2, -size.height / 2))
+        .toList();
+
+    Path path = Path();
+    Paint paint = Paint()
+      ..color = Colors.orange
+      ..style = PaintingStyle.stroke
+      ..strokeWidth = 2;
+    if (pos.length < 3) {
+      canvas.drawPoints(PointMode.points, pos, _helpPaint..strokeWidth = 8);
+    } else {
+      path.moveTo(pos[0].dx, pos[0].dy);
+      path.quadraticBezierTo(pos[1].dx, pos[1].dy, pos[2].dx, pos[2].dy);
+      canvas.drawPath(path, paint);
+      _drawHelp(canvas);
+      _drawSelectPos(canvas,size);
+    }
+  }
+
+  void _drawHelp(Canvas canvas) {
+    _helpPaint..color = Colors.purple;
+    canvas.drawPoints(PointMode.polygon, pos, _helpPaint..strokeWidth = 1);
+    canvas.drawPoints(PointMode.points, pos, _helpPaint..strokeWidth = 8);
+  }
+
+  void _drawSelectPos(Canvas canvas,Size size) {
+    Offset? selectPos = repaint.selectPoint;
+    if (selectPos == null) return;
+    selectPos = selectPos.translate(-size.width / 2, -size.height / 2);
+    canvas.drawCircle(
+        selectPos,
+        10,
+        _helpPaint
+          ..color = Colors.green
+          ..strokeWidth = 2);
+  }
+
+  @override
+  bool shouldRepaint(PaperPainter oldDelegate) =>
+      oldDelegate.repaint != repaint;
+}