Flutter：如何使用 CustomPaint 绘制心形

在Flutter中，您可以使用CustomPaint小部件和CustomPainter抽象类来绘制自定义形状。以下是如何使用CustomPaint绘制心形的示例代码：

import 'package:flutter/material.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: HeartPainter(),
        ),
      ),
    );
  }
}
 
class HeartPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = Colors.red
      ..style = PaintingStyle.fill;
 
    final path = Path();
    path.moveTo(size.width * 0.5, size.height * 0.4);
    path.cubicTo(
      size.width * 0.5, size.height * 0.4,
      size.width * 0.25, size.height * 0.7,
      size.width * 0.5, size.height * 0.9,
    );
    path.cubicTo(
      size.width * 0.5, size.height * 0.9,
      size.width * 0.75, size.height * 0.7,
      size.width * 0.5, size.height * 0.4,
    );
 
    canvas.drawPath(path, paint);
  }
 
  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return false;
  }
}

这段代码定义了一个名为HeartPainter的CustomPainter类，它重写了paint方法来创建心形路径，并使用了Canvas来绘制它。然后在MyApp的build方法中，通过Center部件将HeartPainter作为自定义绘画小部件放置在屏幕中心。