颤振如何绘制半圆（半圆）

Create a

StatelessWidget

MyArc

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 classclass 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;}

Usage:

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