如何仅为 UIView 的左上角和右上角设置cornerRadius? [英] How to set cornerRadius for only top-left and top-right corner of a UIView?

问题描述

有没有办法只为 UIView 的左上角和右上角设置 cornerRadius?

Is there a way to set cornerRadius for only top-left and top-right corner of a UIView?

我尝试了以下方法，但最终还是看不到视图.

I tried the following, but it end up not seeing the view anymore.

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;

推荐答案

请注意，如果您附加了布局约束，则必须在您的 UIView 子类中按如下方式刷新它:

Pay attention to the fact that if you have layout constraints attached to it, you must refresh this as follows in your UIView subclass:

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

如果你不这样做，它就不会出现.

If you don't do that it won't show up.

要圆角，请使用扩展名:

And to round corners, use the extension:

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
    }
}

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额外的视图控制器案例:无论你不能或不想子类化一个视图，你仍然可以围绕一个视图.通过覆盖 viewWillLayoutSubviews() 函数从其视图控制器执行此操作，如下所示:

---

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Additional view controller case: Whether you can't or wouldn't want to subclass a view, you can still round a view. Do it from its view controller by overriding the viewWillLayoutSubviews() function, as follows:

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)
    }
}

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