Flutter怎么畫半圓（半圓）

Question

我怎樣才能畫出這樣的半圓？

代碼：

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

創建一個StatelessWidget說MyArc接受一個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),
  );
}

Answer 2

使用簡單的實現（不是最好的）

您可以在一行中繪制 2 個具有相同寬度和高度的容器，並為每個容器提供一個 BoxDectoration => BorderRadius 作為以下代碼，這不是最好的實現，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 3

這是一個使用Stack的簡單代碼。 您可以使用矩形和圓形輕松生成半圓。 使用BoxDecoration(shape:)重塑容器

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,
                        ),
                      ),
                    ],
                  ),

更新：你只需要一個Container ，EASY PEASY：

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

Answer 4

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

使用此代碼，您可以制作一個半圓。

Answer 5

創建一個從 CustomClipper 擴展的類並使用 arcToPoint 方法繪制圓並使用 ClipPath 小部件，這是實現該功能的代碼

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 6

這將起作用，您可以更改尺寸，但要確保高度是邊界半徑的一半，寬度等於邊界半徑。

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