检查GitHub上的示例项目，以确保正确使用组件。

简单的Swift 5解决方案，没有任何额外的子视图或子类化:

extension UIView {

    func addShadow(offset: CGSize, color: UIColor, radius: CGFloat, opacity: Float) {
        layer.masksToBounds = false
        layer.shadowOffset = offset
        layer.shadowColor = color.cgColor
        layer.shadowRadius = radius
        layer.shadowOpacity = opacity

        let backgroundCGColor = backgroundColor?.cgColor
        backgroundColor = nil
        layer.backgroundColor =  backgroundCGColor
    }
}

请注意，在调用addShadow之前，您应该使用角半径和其他属性设置视图。

之后，像这样从viewDidLoad调用这个:

button.addShadow(offset: CGSize.init(width: 0, height: 3), color: UIColor.black, radius: 2.0, opacity: 0.35)

最终结果:

超级简单!

斯威夫特

// corner radius
blueView.layer.cornerRadius = 10

// border
blueView.layer.borderWidth = 1.0
blueView.layer.borderColor = UIColor.black.cgColor

// shadow
blueView.layer.shadowColor = UIColor.black.cgColor
blueView.layer.shadowOffset = CGSize(width: 3, height: 3)
blueView.layer.shadowOpacity = 0.7
blueView.layer.shadowRadius = 4.0

探索选择

问题1:阴影被剪掉了

如果我们希望将子层或子视图(如图像)的内容剪辑到视图的边界，该怎么办?

我们可以用

blueView.layer.masksToBounds = true

(另外,blueView。clipsToBounds = true给出相同的结果。)

但是，哦不!影子也被剪掉了，因为它在边界之外!怎么办呢?怎么办呢?

解决方案

阴影和边界使用单独的视图。基本视图是透明的，并且有阴影。边界视图将它拥有的任何其他子内容剪辑到它的边界。

// add the shadow to the base view
baseView.backgroundColor = UIColor.clear
baseView.layer.shadowColor = UIColor.black.cgColor
baseView.layer.shadowOffset = CGSize(width: 3, height: 3)
baseView.layer.shadowOpacity = 0.7
baseView.layer.shadowRadius = 4.0

// add the border to subview
let borderView = UIView()
borderView.frame = baseView.bounds
borderView.layer.cornerRadius = 10
borderView.layer.borderColor = UIColor.black.cgColor
borderView.layer.borderWidth = 1.0
borderView.layer.masksToBounds = true
baseView.addSubview(borderView)

// add any other subcontent that you want clipped
let otherSubContent = UIImageView()
otherSubContent.image = UIImage(named: "lion")
otherSubContent.frame = borderView.bounds
borderView.addSubview(otherSubContent)

结果如下:

问题2:表现不佳

添加圆角和阴影可以提高性能。您可以通过为阴影使用预定义的路径并指定它是栅格化来提高性能。下面的代码可以添加到上面的示例中。

baseView.layer.shadowPath = UIBezierPath(roundedRect: baseView.bounds, cornerRadius: 10).cgPath
baseView.layer.shouldRasterize = true
baseView.layer.rasterizationScale = UIScreen.main.scale

更多细节请看这篇文章。看这里和这里。

我们用Swift 4和Xcode 9测试了这个答案。

var shadows = UIView()
shadows.frame = view.frame
shadows.clipsToBounds = false
view.addSubview(shadows)


let shadowPath0 = UIBezierPath(roundedRect: shadows.bounds, cornerRadius: 10)
let layer0 = CALayer()
layer0.shadowPath = shadowPath0.cgPath
layer0.shadowColor = UIColor(red: 0, green: 0, blue: 0, alpha: 0.23).cgColor
layer0.shadowOpacity = 1
layer0.shadowRadius = 6
layer0.shadowOffset = CGSize(width: 0, height: 3)
layer0.bounds = shadows.bounds
layer0.position = shadows.center

shadows.layer.addSublayer(layer0)

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:

这就是你怎么做的，有圆角和圆角阴影，而不用担心路径。

//Inner view with content
[imageView.layer setBorderColor:[[UIColor lightGrayColor] CGColor]];
[imageView.layer setBorderWidth:1.0f];
[imageView.layer setCornerRadius:8.0f];
[imageView.layer setMasksToBounds:YES];

//Outer view with shadow
UIView* shadowContainer = [[UIView alloc] initWithFrame:imageView.frame];
[shadowContainer.layer setMasksToBounds:NO];
[shadowContainer.layer setShadowColor:[[UIColor blackColor] CGColor]];
[shadowContainer.layer setShadowOpacity:0.6f];
[shadowContainer.layer setShadowRadius:2.0f];
[shadowContainer.layer setShadowOffset: CGSizeMake(0.0f, 2.0f)];

[shadowContainer addSubview:imageView];

带有内容的视图，在我的例子中是UIImageView，有一个角半径，因此必须屏蔽到边界。

我们为阴影创建另一个同样大小的视图，设置它的maskToBounds为NO，然后将内容视图添加到容器视图(例如shadowContainer)。

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:)