画布上的CustomPainter路径附加线

import 'package:flutter/material.dart';

class MyCustomPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint()
      ..color = Colors.blue
      ..strokeWidth = 2.0
      ..style = PaintingStyle.stroke;

    Path path = Path()
      ..moveTo(50, 50)
      ..lineTo(200, 50)
      ..lineTo(200, 200)
      ..lineTo(50, 200)
      ..lineTo(50, 50);

    canvas.drawPath(path, paint);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return false;
  }
}

class MyCustomPaintWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      painter: MyCustomPainter(),
      child: Container(
        width: 250,
        height: 250,
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      appBar: AppBar(
        title: Text('Custom Painter Example'),
      ),
      body: Center(
        child: MyCustomPaintWidget(),
      ),
    ),
  ));
}