Flutter如何画半圆（半圆）

Question

如何画这样的半圆？

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;
  }

Answer 1

创建一个

StatelessWidget

说

MyArc

接受

diameter

。

import 'dart:math' as math;

class MyArc extends StatelessWidget {
  final double diameter;

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

  @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;
}

用途：

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

Answer 2

Container(
    decoration: const BoxDecoration(
      color: Colors.black,
      borderRadius: BorderRadius.only(
        bottomLeft: Radius.circular(100),
        bottomRight: Radius.circular(100),
      ),

使用此代码，您可以制作半圆。

Answer 3

创建一个从 CustomClipper 扩展的类，并使用 arcToPoint 方法来绘制圆并使用 ClipPath 小部件，这是实现该功能的代码

ClipPath(
      clipper: CustomClip(),
      child: Container(
        width: 200,
        height: 100,
        color: Colors.blue,
      ),
    ),

    class CustomClip extends CustomClipper<Path> {
      @override
      Path getClip(Size size) {
        double radius = 100;
    
        Path path = Path();
        path
          ..moveTo(size.width / 2, 0)
          ..arcToPoint(Offset(size.width, size.height),
              radius: Radius.circular(radius))
          ..lineTo(0, size.height)
          ..arcToPoint(
            Offset(size.width / 2, 0),
            radius: Radius.circular(radius),
          )
          ..close();
    
        return path;
      }
    
      @override
      bool shouldReclip(covariant CustomClipper<Path> oldClipper) {
        return true;
      }
    }

Answer 4

有一个简单的实现（不是最好的）

您可以在一行内绘制两个具有相同宽度和高度的容器 并为每个容器提供一个 BoxDectoration => BorderRadius 如下面的代码， 这不是最好的实现，它只是有效

Row(children: [

          Container(
            decoration: BoxDecoration(
              borderRadius: BorderRadius.only(topRight: Radius.circular(200),),
            color: Colors.blue[300],
            ),
            width: 200,
            height: 200,
            ),
            Container(
            decoration: BoxDecoration(
              borderRadius: BorderRadius.only(topLeft: Radius.circular(200),),
            color: Colors.blue[300],
            ),
            width: 200,
            height: 200,
            )

], ),

Answer 5

更新：你只需要一个

Container

，简单方便：

Container(
                          decoration: BoxDecoration(
                            borderRadius: BorderRadius.only(
                                bottomLeft: Radius.circular(100),
                                topLeft: Radius.circular(100)),
                            color: Colors.red,
                            shape: BoxShape.rectangle,
                          ),
                          height: 35,
                          width: 35,
                        ),

这是使用

Stack

的简单代码。您可以使用矩形和圆形轻松生成半圆。用

BoxDecoration(shape:)

重塑容器形状

Stack(
   children: [
        Align(
           alignment: Alignment.center,
           child: Container(
                height: 35,
                          width: 35,
                          decoration: BoxDecoration(
                            color: Colors.red,
                            shape: BoxShape.circle,
                          ),
                        ),
                      ),
                      Align(
                        alignment: Alignment.centerLeft,
                        child: Container(
                          decoration: BoxDecoration(
                            color: Colors.red,
                            shape: BoxShape.rectangle,
                          ),
                          height: 35,
                          width: 35,
                        ),
                      ),
                    ],
                  ),

Answer 6

这可行，您可以更改尺寸，但请确保高度是 borderRadius 的一半，宽度等于 borderRadius。

Container(
height: 50,
         width:100,
    decoration: const BoxDecoration(
      color: Colors.black,
      borderRadius: BorderRadius.only(
        bottomLeft: Radius.circular(100),
        bottomRight: Radius.circular(100),
      ))),

Answer 7

Container(
          width: 100,
          height: 50,
          decoration: const BoxDecoration(
            border: Border(
              left: BorderSide(
                color: Colors.green,
                width: 20,
              ),
              right: BorderSide(
                color: Colors.green,
                width: 20,
              ),
              bottom: BorderSide(
                color: Colors.green,
                width: 20,
              ),
            ),
            borderRadius: BorderRadius.only(
              bottomLeft: Radius.circular(200),
              bottomRight: Radius.circular(200),
            ),
          ),
        ),