如何将UIView裁剪为半圆？

Question

我想以半圆形状裁剪UIView

提前致谢。

Answer 1

此问题已在此处得到解答：Draw a semi-circle button iOS

这是该问题的摘录，但使用的是UIView：

Swift 3

let myView = [this should be your view]
let circlePath = UIBezierPath.init(arcCenter: CGPoint(x: myView.bounds.size.width / 2, y: 0), radius: myView.bounds.size.height, startAngle: 0.0, endAngle: CGFloat(M_PI), clockwise: true)
let circleShape = CAShapeLayer()
circleShape.path = circlePath.cgPath
myView.layer.mask = circleShape

Swift 4

let myView = [this should be your view]
let circlePath = UIBezierPath.init(arcCenter: CGPoint(x: myView.bounds.size.width / 2, y: 0), radius: myView.bounds.size.height, startAngle: 0.0, endAngle: .pi, clockwise: true)
let circleShape = CAShapeLayer()
circleShape.path = circlePath.cgPath
myView.layer.mask = circleShape

我希望这有助于你

Answer 2

一种方便的方法就是将UIView作为子类，在其上添加一个图层，如果不是默认情况下，则使视图颜色透明。

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
        }
    }    
}

Answer 3

此问题的处理速度为Swift 4和Swift 5。

let yourView =（是您要从顶部裁剪半圆的视图）

 let circlePath = UIBezierPath(arcCenter: CGPoint(x: yourView.bounds.size.width / 2, y: yourView.bounds.size.height), radius: yourView.bounds.size.height, startAngle: 0.0, endAngle: .pi, clockwise: false)
    let circleShape = CAShapeLayer()
    circleShape.path = circlePath.cgPath
    yourView.layer.mask = circleShape