丹尼尔。Gindi上面的回答对我很有用!然而，我不得不做一些小的调整-改变shadowFrame的大小与视图的帧大小相同，并启用用户交互。以下是更新后的代码:

+ (UIView*)putView:(UIView*)view insideShadowWithColor:(UIColor*)color andRadius:(CGFloat)shadowRadius andOffset:(CGSize)shadowOffset andOpacity:(CGFloat)shadowOpacity
{
    CGRect shadowFrame; // Modify this if needed

    // Modified this line
    shadowFrame.size = CGSizeMake(view.frame.size.width, view.frame.size.height);

    shadowFrame.origin.x = 0.f;
    shadowFrame.origin.y = 0.f;
    UIView * shadow = [[UIView alloc] initWithFrame:shadowFrame];

    // Modified this line
    shadow.userInteractionEnabled = YES;
    shadow.layer.shadowColor = color.CGColor;
    shadow.layer.shadowOffset = shadowOffset;
    shadow.layer.shadowRadius = shadowRadius;
    shadow.layer.masksToBounds = NO;
    shadow.clipsToBounds = NO;
    shadow.layer.shadowOpacity = shadowOpacity;

    [shadow addSubview:view];
    return shadow;
}

我想补充的是，在我的情况下，我试图将此添加到第三方视图控制器，即我没有对代码的直接控制。下面是我如何使用上面的函数:

UIView *shadow = [self putView:vc.view 
         insideShadowWithColor:[UIColor blackColor]
                     andRadius:5.0 
                     andOffset:CGSizeMake(0.0, 0.0) 
                    andOpacity:1.0];
vc.view = shadow;
vc.view.layer.cornerRadius = 5.0;
vc.view.layer.masksToBounds = YES;

这是我的版本在Swift 3的UIView

let corners:UIRectCorner = [.bottomLeft, .topRight]
let path = UIBezierPath(roundedRect: rect, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
let mask = CAShapeLayer()

mask.path = path.cgPath
mask.fillColor = UIColor.white.cgColor

let shadowLayer = CAShapeLayer()
shadowLayer.shadowColor = UIColor.black.cgColor
shadowLayer.shadowOffset = CGSize(width: 0.0, height: 4.0)
shadowLayer.shadowRadius = 6.0
shadowLayer.shadowOpacity = 0.25
shadowLayer.shadowPath = mask.path

self.layer.insertSublayer(shadowLayer, at: 0)
self.layer.insertSublayer(mask, at: 1)

如果你因为圆角、子视图和masksToBounds而挣扎，那么尝试使用我的函数:

- (UIView*)putView:(UIView*)view insideShadowWithColor:(UIColor*)color andRadius:(CGFloat)shadowRadius andOffset:(CGSize)shadowOffset andOpacity:(CGFloat)shadowOpacity
{
    CGRect shadowFrame; // Modify this if needed
    shadowFrame.size.width = 0.f;
    shadowFrame.size.height = 0.f;
    shadowFrame.origin.x = 0.f;
    shadowFrame.origin.y = 0.f;
    UIView * shadow = [[UIView alloc] initWithFrame:shadowFrame];
    shadow.userInteractionEnabled = NO; // Modify this if needed
    shadow.layer.shadowColor = color.CGColor;
    shadow.layer.shadowOffset = shadowOffset;
    shadow.layer.shadowRadius = shadowRadius;
    shadow.layer.masksToBounds = NO;
    shadow.clipsToBounds = NO;
    shadow.layer.shadowOpacity = shadowOpacity;
    [view.superview insertSubview:shadow belowSubview:view];
    [shadow addSubview:view];
    return shadow;
}

在你的视图中调用它。无论你的视图是否有圆角，无论它的大小，它的形状-一个漂亮的阴影将被绘制出来。

只要保留函数的返回值，这样当你想要删除表时就可以引用它(或者例如使用insertSubview:aboveView:)

当为容器视图分配阴影路径时，我使用以下技巧解决了这个问题:

[UIBezierPath bezierPathWithRoundedRect:cell.bounds cornerRadius:12]

请注意，阴影的路径是一个圆角矩形，与单元格包含的背景具有相同的角半径:

//this is the border for the UIView that is added to a cell
cell.backgroundView.layer.cornerRadius = 12;
cell.backgroundView.layer.masksToBounds = YES;
cell.backgroundView.layer.borderColor = [UIColor darkGrayColor].CGColor;
cell.backgroundView.layer.borderWidth = 1;

//this is the shadow around the cell itself (cannot have round corners with borders and shadow, need to use two views
cell.layer.shadowRadius = 2;
cell.layer.cornerRadius = 12;
cell.layer.masksToBounds = NO;
[[cell layer] setShadowColor:[[UIColor darkGrayColor] CGColor]];

[[cell layer] setShadowOffset:CGSizeMake(0.0,0.0)];
[[cell layer] setShadowOpacity:1.0];

UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:cell.bounds cornerRadius:12];
[[cell layer] setShadowPath:[path CGPath]];

旧线程仍然当前…

我编辑了Daniel Gindi的方法，使它可以用于按钮等。 如果有人需要圆角，或者想要将圆角和边框结合起来，它必须在视图层上设置，这个视图层被传递给这个方法。我还设置了栅格化来加快一点。

+ (UIView*)putView:(UIView*)view insideShadowWithColor:(CGColorRef)color 
                                 andRadius:(CGFloat)shadowRadius 
                                 andOffset:(CGSize)shadowOffset 
                                 andOpacity:(CGFloat)shadowOpacity
{
    // Must have same position like "view"
    UIView *shadow = [[UIView alloc] initWithFrame:view.frame]; 

    shadow.layer.contentsScale = [UIScreen mainScreen].scale;
    shadow.userInteractionEnabled = YES; // Modify this if needed
    shadow.layer.shadowColor = color;
    shadow.layer.shadowOffset = shadowOffset;
    shadow.layer.shadowRadius = shadowRadius;
    shadow.layer.masksToBounds = NO;
    shadow.clipsToBounds = NO;
    shadow.layer.shadowOpacity = shadowOpacity;
    shadow.layer.rasterizationScale = [UIScreen mainScreen].scale;
    shadow.layer.shouldRasterize = YES;

    [view.superview insertSubview:shadow belowSubview:view];
    [shadow addSubview:view];

    // Move view to the top left corner inside the shadowview 
    // ---> Buttons etc are working again :)
    view.frame = CGRectMake(0, 0, view.frame.size.width, view.frame.size.height);

    return shadow;
}

import UIKit

extension UIView {

    func addShadow(shadowColor: UIColor, offSet: CGSize, opacity: Float, shadowRadius: CGFloat, cornerRadius: CGFloat, corners: UIRectCorner, fillColor: UIColor = .white) {

        let shadowLayer = CAShapeLayer()
        let size = CGSize(width: cornerRadius, height: cornerRadius)
        let cgPath = UIBezierPath(roundedRect: self.bounds, byRoundingCorners: corners, cornerRadii: size).cgPath //1
        shadowLayer.path = cgPath //2
        shadowLayer.fillColor = fillColor.cgColor //3
        shadowLayer.shadowColor = shadowColor.cgColor //4
        shadowLayer.shadowPath = cgPath
        shadowLayer.shadowOffset = offSet //5
        shadowLayer.shadowOpacity = opacity
        shadowLayer.shadowRadius = shadowRadius
        self.layer.addSublayer(shadowLayer)
    }
}