Flutter 如何画半圆(半圆) [英] Flutter how to draw semicircle (half circle)

问题描述

这样的半圆怎么画?

代码:

class DrawHalfCircleClipper extends CustomClipper<Path> {
  @override
  Path getClip(Size size) {
    final Path path = new Path();
    ...
    return path;
  }
  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) {
    return true;
  }

推荐答案

创建一个 StatelessWidget 说 MyArc 它接受一个 diameter.

Create a StatelessWidget say MyArc which accepts a diameter.

class MyArc extends StatelessWidget {
  final double diameter;

  const MyArc({Key key, this.diameter = 200}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      painter: MyPainter(),
      size: Size(diameter, diameter),
    );
  }
}

// This is the Painter class
class MyPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint()..color = Colors.blue;
    canvas.drawArc(
      Rect.fromCenter(
        center: Offset(size.height / 2, size.width / 2),
        height: size.height,
        width: size.width,
      ),
      math.pi,
      math.pi,
      false,
      paint,
    );
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => false;
}

用法:

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(),
    body: MyArc(diameter: 300),
  );
}

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