使用这个扩展设置角圆角和圆角边界

像这样使用:

override func viewWillLayoutSubviews() {
            super.viewWillLayoutSubviews()

         myView.roundCornersWithBorder(corners: [.topLeft, .topRight], radius: 8.0)
    
        myView.roundCorners(corners: [.topLeft, .topRight], radius: 8.0)

        }



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
    }
    
    func roundCornersWithBorder(corners: UIRectCorner, radius: CGFloat) {
        let maskLayer = CAShapeLayer()
        maskLayer.frame = bounds
        maskLayer.path = UIBezierPath(roundedRect: bounds, byRoundingCorners: [.topLeft, .topRight], cornerRadii: CGSize(width: radius, height: radius)).cgPath
        
        layer.mask = maskLayer
        
        // Add border
        let borderLayer = CAShapeLayer()
        borderLayer.path = maskLayer.path // Reuse the Bezier path
        borderLayer.fillColor = UIColor.clear.cgColor
        borderLayer.strokeColor = UIColor(red:3/255, green:33/255, blue:70/255, alpha: 0.15).cgColor
        borderLayer.lineWidth = 2
        borderLayer.frame = bounds
        layer.addSublayer(borderLayer)
    }
    
}

最简单的方法是用圆角层做一个蒙版。

CALayer *maskLayer = [CALayer layer];
maskLayer.frame = CGRectMake(0,0,maskWidth ,maskHeight);
maskLayer.contents = (__bridge id)[[UIImage imageNamed:@"maskImageWithRoundedCorners.png"] CGImage];

aUIView.layer.mask = maskLayer;

别忘了:

#import <QuartzCore/QuartzCore.h>

使用这个扩展，它将涵盖一切。

extension UIView {

   func roundTopCorners(radius: CGFloat = 10) {
    
       self.clipsToBounds = true
       self.layer.cornerRadius = radius
       if #available(iOS 11.0, *) {
           self.layer.maskedCorners = [.layerMinXMinYCorner, .layerMaxXMinYCorner]
       } else {
           self.roundCorners(corners: [.topLeft, .topRight], radius: radius)
       }
   }

   func roundBottomCorners(radius: CGFloat = 10) {
    
       self.clipsToBounds = true
       self.layer.cornerRadius = radius
       if #available(iOS 11.0, *) {
           self.layer.maskedCorners = [.layerMinXMaxYCorner, .layerMaxXMaxYCorner]
       } else {
           self.roundCorners(corners: [.bottomLeft, .bottomRight], radius: radius)
       }
   }

   private 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
    }
}

然后像这样使用它:-

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
            
    self.yourView.roundTopCorners()
}

注意:-我建议你不要把这段代码放在viewDidLayoutSubviews()中，因为每当视图更新时，你都会在里面得到调用。所以使用viewDidAppear()，它会像一个咒语一样工作。

所有已经给出的答案都是非常好的和有效的(特别是尤努斯使用蒙版属性的想法)。

然而，我需要一些更复杂的东西，因为我的层可以经常改变大小，这意味着我需要每次都调用掩蔽逻辑，这有点烦人。

我使用了swift扩展和计算属性来构建一个真正的cornerRadii属性，它负责在图层布局时自动更新蒙版。

这是使用Peter Steinberg伟大的Aspects库实现的。

完整代码在这里:

extension CALayer {
  // This will hold the keys for the runtime property associations
  private struct AssociationKey {
    static var CornerRect:Int8 = 1    // for the UIRectCorner argument
    static var CornerRadius:Int8 = 2  // for the radius argument
  }

  // new computed property on CALayer
  // You send the corners you want to round (ex. [.TopLeft, .BottomLeft])
  // and the radius at which you want the corners to be round
  var cornerRadii:(corners: UIRectCorner, radius:CGFloat) {
    get {
      let number = objc_getAssociatedObject(self, &AssociationKey.CornerRect)  as? NSNumber ?? 0
      let radius = objc_getAssociatedObject(self, &AssociationKey.CornerRadius)  as? NSNumber ?? 0
      return (corners: UIRectCorner(rawValue: number.unsignedLongValue), radius: CGFloat(radius.floatValue))
    }
    set (v) {
      let radius = v.radius
      let closure:((Void)->Void) = {
        let path = UIBezierPath(roundedRect: self.bounds, byRoundingCorners: v.corners, cornerRadii: CGSize(width: radius, height: radius))
        let mask = CAShapeLayer()
        mask.path = path.CGPath
        self.mask = mask
      }
      let block: @convention(block) Void -> Void = closure
      let objectBlock = unsafeBitCast(block, AnyObject.self)
      objc_setAssociatedObject(self, &AssociationKey.CornerRect, NSNumber(unsignedLong: v.corners.rawValue), .OBJC_ASSOCIATION_RETAIN)
      objc_setAssociatedObject(self, &AssociationKey.CornerRadius, NSNumber(float: Float(v.radius)), .OBJC_ASSOCIATION_RETAIN)
      do { try aspect_hookSelector("layoutSublayers", withOptions: .PositionAfter, usingBlock: objectBlock) }
      catch _ { }
    }
  }
}

我写了一篇简单的博客来解释这一点。

斯威夫特4

extension UIView {

    func roundTop(radius:CGFloat = 5){
        self.clipsToBounds = true
        self.layer.cornerRadius = radius
        if #available(iOS 11.0, *) {
            self.layer.maskedCorners = [.layerMaxXMinYCorner, .layerMinXMinYCorner]
        } else {
            // Fallback on earlier versions
        }
    }

    func roundBottom(radius:CGFloat = 5){
        self.clipsToBounds = true
        self.layer.cornerRadius = radius
        if #available(iOS 11.0, *) {
            self.layer.maskedCorners = [.layerMaxXMaxYCorner, .layerMinXMaxYCorner]
        } else {
            // Fallback on earlier versions
        }
    }
}

有一个超级简单的方法。我在这里找到的。

view.clipsToBounds = true
view.layer.cornerRadius = 24
view.layer.maskedCorners = [.layerMinXMinYCorner, .layerMaxXMinYCorner]

它在视图的CALayer上使用stock cornerRadius属性。你只需要定义这些角。layerMinXMinYCorner是左上layerMaxXMinYCorner是右上。