Evan Mulawski提供的答案将会非常有效。问题是你必须将视图的背景色设置为clearColor，并将masksToBounds属性设置为NO。

你可以为视图设置任何你想要的颜色

v.layer.backgroundColor = your color;

希望这能有所帮助。

这里有一个肯定有效的解决方案!

我已经创建了UIView扩展所需的边应用阴影如下

enum AIEdge:Int {
    case
    Top,
    Left,
    Bottom,
    Right,
    Top_Left,
    Top_Right,
    Bottom_Left,
    Bottom_Right,
    All,
    None
}

extension UIView {
        
    func applyShadowWithCornerRadius(color:UIColor, opacity:Float, radius: CGFloat, edge:AIEdge, shadowSpace:CGFloat, cornerRadius: CGFloat)    {

        var sizeOffset:CGSize = CGSize.zero
        
        switch edge {
        case .Top:
            sizeOffset = CGSize(width: 0, height: -shadowSpace)
        case .Left:
            sizeOffset = CGSize(width: -shadowSpace, height: 0)
        case .Bottom:
            sizeOffset = CGSize(width: 0, height: shadowSpace)
        case .Right:
            sizeOffset = CGSize(width: shadowSpace, height: 0)
            
            
        case .Top_Left:
            sizeOffset = CGSize(width: -shadowSpace, height: -shadowSpace)
        case .Top_Right:
            sizeOffset = CGSize(width: shadowSpace, height: -shadowSpace)
        case .Bottom_Left:
            sizeOffset = CGSize(width: -shadowSpace, height: shadowSpace)
        case .Bottom_Right:
            sizeOffset = CGSize(width: shadowSpace, height: shadowSpace)
            
            
        case .All:
            sizeOffset = CGSize(width: 0, height: 0)
        case .None:
            sizeOffset = CGSize.zero
        }

        self.layer.cornerRadius = cornerRadius
        self.layer.masksToBounds = true

        self.layer.shadowColor = color.cgColor
        self.layer.shadowOpacity = opacity
        self.layer.shadowOffset = sizeOffset
        self.layer.shadowRadius = radius
        self.layer.masksToBounds = false

        self.layer.shadowPath = UIBezierPath(roundedRect:self.bounds, cornerRadius:self.layer.cornerRadius).cgPath
    }
}

最后，你可以为你的UIView子类调用下面的阴影函数，你也可以指定边缘上应用阴影，尝试不同的变化根据你需要改变下面方法调用的参数。

viewRoundedToBeShadowedAsWell.applyShadowWithCornerRadius(color: .gray, opacity: 1, radius: 15, edge: AIEdge.All, shadowSpace: 15)

注意:如果仍然不工作，试着从主线程调用它

DispatchQueue.main.async {
   viewRoundedToBeShadowedAsWell.applyShadowWithCornerRadius(color: .gray, opacity: 1, radius: 15, edge: AIEdge.All, shadowSpace: 15)
}

希望有人觉得这有用!

以下是结果图片:

你需要使用两个uiview来实现这一点。一个UIView会像阴影一样工作，另一个会为圆角边界工作。

下面是一个在协议帮助下的类方法的代码片段:

@implementation UIMethods

+ (UIView *)genComposeButton:(UIViewController <UIComposeButtonDelegate> *)observer;
{
    UIView *shadow = [[UIView alloc]init];
    shadow.layer.cornerRadius = 5.0;
    shadow.layer.shadowColor = [[UIColor blackColor] CGColor];
    shadow.layer.shadowOpacity = 1.0;
    shadow.layer.shadowRadius = 10.0;
    shadow.layer.shadowOffset = CGSizeMake(0.0f, -0.5f);

    UIButton *btnCompose = [[UIButton alloc]initWithFrame:CGRectMake(0, 0,60, 60)];
    [btnCompose setUserInteractionEnabled:YES];
    btnCompose.layer.cornerRadius = 30;
    btnCompose.layer.masksToBounds = YES;
    [btnCompose setImage:[UIImage imageNamed:@"60x60"] forState:UIControlStateNormal];
    [btnCompose addTarget:observer action:@selector(btnCompose_click:) forControlEvents:UIControlEventTouchUpInside];
    [shadow addSubview:btnCompose];
    return shadow;
}

在上面的代码中，btnCompose_click:将成为一个@required委托方法，该方法将在单击按钮时触发。

在这里我添加了一个按钮到我的UIViewController，像这样:

UIView *btnCompose = [UIMethods genComposeButton:self];
btnCompose.frame = CGRectMake(self.view.frame.size.width - 75,
                          self.view.frame.size.height - 75,
                          60, 60);
[self.view addSubview:btnCompose];

结果如下所示:

在研究了一整天的圆角视图与阴影之后，我很高兴在这里发布我的自定义uiview类，希望结束这个问题:

RoundCornerShadowView.h

#import <UIKit/UIKit.h>

@interface RoundCornerShadowView : UIView

@end

RoundCornerShadowView.m

#import "RoundCornerShadowView.h"

@implementation RoundCornerShadowView

// *** must override this method, not the other method ***
// otherwise, the background corner doesn't disappear....
// @2015/05/29
-(void) layoutSubviews {
    [super layoutSubviews];//is must to ensure rightly layout children view

    //1. first, create Inner layer with content
    CALayer *innerView = [CALayer layer];
    innerView.frame = CGRectMake(0,0,self.bounds.size.width,self.bounds.size.height);
    //instead of: innerView.frame = self.frame;
    innerView.borderWidth = 1.0f;
    innerView.cornerRadius = 6.0f;
    innerView.masksToBounds = YES;
    innerView.borderColor = [[UIColor lightGrayColor] CGColor];
    innerView.backgroundColor = [[UIColor whiteColor] CGColor];
    //put the layer to the BOTTOM of layers is also a MUST step...
    //otherwise this layer will overlay the sub uiviews in current uiview...
    [self.layer insertSublayer:innerView atIndex:0];

    //2. then, create shadow with self layer
    self.layer.masksToBounds = NO;
    self.layer.shadowColor = [[UIColor darkGrayColor] CGColor];
    self.layer.shadowOpacity = 0.4f;
    //shadow length
    self.layer.shadowRadius = 2.0f;
    //no offset
    self.layer.shadowOffset = CGSizeMake(0, 0);
    //right down shadow
    //[self.layer setShadowOffset: CGSizeMake(1.0f, 1.0f)];

    //3. last but important, MUST clear current view background color, or the color will show in the corner!
    self.backgroundColor = [UIColor clearColor];
}

@end

所以，不需要在视图中添加子视图或在目标视图中添加子视图，只需在当前视图中添加一层，并执行3步即可完成!

仔细查看代码中的注释，这有助于理解组件!

Swift 4解决方案，使UICollectionViewCell圆形和添加阴影，没有任何扩展和并发症:)

注意:对于简单的视图，例如按钮。请看这篇文章中的@suragch的回答。 https://stackoverflow.com/a/34984063/7698092。按钮测试成功

以防有人还在努力使角落圆润，同时添加阴影。虽然这个解决方案适用于UICollectionViewCell，但它可以推广到任何视图。

这个技巧对我来说很有效，不需要做任何扩展和所有复杂的事情。我正在使用storyBoard。

技术

你必须在storyBoard的UICollectionViewCell中添加一个UIView(让我们说它是“containerView”)，并在这个containerView中添加所有必需的视图(按钮，图像等)。 见截图。

连接containerView的出口。在CellforItemAtIndexPath委托函数中添加以下代码行。

//adds shadow to the layer of cell

cell.layer.cornerRadius = 3.0
    cell.layer.masksToBounds = false
    cell.layer.shadowColor = UIColor.black.cgColor
    cell.layer.shadowOffset = CGSize(width: 0, height: 0)
    cell.layer.shadowOpacity = 0.6

//makes the cell round 

let containerView = cell.containerView!
    containerView.layer.cornerRadius = 8
    containerView.clipsToBounds = true

输出

查看模拟器截图

你需要使用shadowView和roundView

shadowView

必须有背景色 应该躺在roundView后面吗 窍门是将shadowView布局在里面，它的阴影需要发光。调整嵌入，使shadowView在roundView后面完全不可见

圆视图

必须剪辑子视图

的代码

addSubviews(shadowView, roundView)
roundView.addSubviews(titleLabel, subtitleLabel, imageView)

// need inset
shadowView.pinEdges(view: self, inset: UIEdgeInsets(constraintInsets: 2))
roundView.pinEdges(view: self)

do {
  shadowView.backgroundColor = .white // need background
  let layer = shadowView.layer
  layer.shadowColor = UIColor.black.cgColor
  layer.shadowRadius = 3
  layer.shadowOffset = CGSize(width: 3, height: 3)
  layer.shadowOpacity = 0.7
  layer.shouldRasterize = true
}

do {
  roundView.backgroundColor = .white
  let layer = roundView.layer
  layer.masksToBounds = true
  layer.cornerRadius = 5
}

或者你可以在不指定clipToBounds/maskToBounds的情况下这样做

layer.shadowColor = UIColor.gray.cgColor
layer.shadowOffset = CGSize(width: 3, height: 3)
layer.shadowOpacity = 0.8