swift – 如何将UIView裁剪为半圆？

我想以半圆形状裁剪UIView

提前致谢.

一个方便的方法是UIView的子类,在它上面添加一个图层,如果默认情况下不是透明的话,使视图颜色透明.

import UIKit

class SemiCirleView: UIView {

    var semiCirleLayer: CAShapeLayer!

    override func layoutSubviews() {
        super.layoutSubviews()

        if semiCirleLayer == nil {
            let arcCenter = CGPoint(x: bounds.size.width / 2,y: bounds.size.height / 2)
            let circleRadius = bounds.size.width / 2
            let circlePath = UIBezierPath(arcCenter: arcCenter,radius: circleRadius,startAngle: CGFloat.pi,endAngle: CGFloat.pi * 2,clockwise: true)

            semiCirleLayer = CAShapeLayer()
            semiCirleLayer.path = circlePath.cgPath
            semiCirleLayer.fillColor = UIColor.red.cgColor
            layer.addSublayer(semiCirleLayer)

            // Make the view color transparent
            backgroundColor = UIColor.clear
        }
    }    
}