ios - 如何只为UIView的左上角和右上角设置cornerRadius？

有没有一种方法可以只为cornerRadius的左上角和右上角设置UIView？

我尝试了以下操作，但最终看不到该 View 了。

UIView *view = [[UIView alloc] initWithFrame:frame];

CALayer *layer = [CALayer layer];
UIBezierPath *shadowPath = [UIBezierPath bezierPathWithRoundedRect:frame byRoundingCorners:(UIRectCornerTopLeft|UIRectCornerTopRight) cornerRadii:CGSizeMake(3.0, 3.0)];
layer.shadowPath = shadowPath.CGPath;
view.layer.mask = layer;

最佳答案

请注意以下事实:如果您附加了布局约束，则必须在UIView子类中按如下所示刷新它:

override func layoutSubviews() {
    super.layoutSubviews()
    roundCorners(corners: [.topLeft, .topRight], radius: 3.0)
}

如果您不这样做，它将不会显示。

要扩展到角落，请使用扩展名:

extension UIView {
   func roundCorners(corners: UIRectCorner, radius: CGFloat) {
        let path = UIBezierPath(roundedRect: bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
        let mask = CAShapeLayer()
        mask.path = path.cgPath
        layer.mask = mask
    }
}

其他 View Controller 案例:无论是否希望对 View 进行子类化，您仍然可以对 View 进行四舍五入。通过覆盖viewWillLayoutSubviews()函数，从其 View Controller 执行此操作，如下所示:

class MyVC: UIViewController {
    /// The view to round the top-left and top-right hand corners
    let theView: UIView = {
        let v = UIView(frame: CGRect(x: 10, y: 10, width: 200, height: 200))
        v.backgroundColor = .red
        return v
    }()

    override func loadView() {
        super.loadView()
        view.addSubview(theView)
    }

    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()

        // Call the roundCorners() func right there.
        theView.roundCorners(corners: [.topLeft, .topRight], radius: 30)
    }
}