在 UIView 顶部添加内部阴影

Question

我查了一下，但找不到如何向 UIView 添加内部阴影，对于 Swift，只有顶部（从上到下）。在 Swift 中添加内圈的最佳方法是什么？

编辑：我在 SO 上找到了一些问题和答案，但是它们要么在 obj-c 中，要么看起来很复杂。我只是在寻找一种更 Swifty 的方式，如果有的话

我想要达到的目标：

Answer 1

Swift 5 扩展

extension UIView {
    func addInnerShadow() {
        let innerShadow = CALayer()
        innerShadow.frame = bounds
        
        // Shadow path (1pt ring around bounds)
        let radius = self.layer.cornerRadius
        let path = UIBezierPath(roundedRect: innerShadow.bounds.insetBy(dx: 2, dy:2), cornerRadius:radius)
        let cutout = UIBezierPath(roundedRect: innerShadow.bounds, cornerRadius:radius).reversing()
        
        path.append(cutout)
        innerShadow.shadowPath = path.cgPath
        innerShadow.masksToBounds = true
        
        // Shadow properties
        innerShadow.shadowColor = UIColor.black.cgColor
        innerShadow.shadowOffset = CGSize(width: 0, height: 0)
        innerShadow.shadowOpacity = 0.5
        innerShadow.shadowRadius = 2
        innerShadow.cornerRadius = self.layer.cornerRadius
        layer.addSublayer(innerShadow)
    }
}

Answer 2

如果您不介意使用clipsToBounds = true，您可以在视图边缘创建一个新的CALayer 偏移并将阴影添加到该视图。这就是 J.Hunter 的回答。

J.Hunter 的代码添加了顶部阴影，这里我将其更新为 Swift 5 并添加到底部。

斯威夫特 5：

override func draw(_ rect: CGRect) {
  // Create Inner Shadow. Not sure about efficiency of this.
  // You may want to create a shadowLayer property
  //  and only run this code if it hasn't been created yet.
  let size = rect.size
  clipsToBounds = true // Don't want to see your fake view layer
  let innerShadowLayer: CALayer = CALayer()
  
  // Need to set a backgroundColor or it doesn't work
  innerShadowLayer.backgroundColor = UIColor.black.cgColor
  
  // Position your shadow layer (anchor point is in the center)
  //  on the edge of where your shadow needs to be.
  // In my case this moves the shadow layer to the
  //  bottom edge of my view
  innerShadowLayer.position = CGPoint(x: size.width / 2, y: size.height + (size.height / 2))
  
  // This could be smaller I think, just copying J.Hunter's code...
  innerShadowLayer.bounds = CGRect(x: 0, y: 0, width: size.width, height: size.height)
  
  // Normal shadow layer properties you'd use for an outer shadow
  innerShadowLayer.shadowColor = UIColor.black.cgColor
  innerShadowLayer.shadowOffset = CGSize(width: 0, height: 0)
  innerShadowLayer.shadowOpacity = 0.3
  innerShadowLayer.shadowRadius = 3
  
  layer.addSublayer(innerShadowLayer)
}

Answer 3

我使用 clear 作为toColor 调整了@anoop4real 所做的修改，并使界面更符合 CALayer 中的阴影设置，包括默认值，不透明度除外，默认情况下设置为 0.0。我选择了默认值 0.6，因为它看起来最自然。

extension UIView {
    func addShadow(to edges: [UIRectEdge], radius: CGFloat = 3.0, opacity: Float = 0.6, color: CGColor = UIColor.black.cgColor) {

        let fromColor = color
        let toColor = UIColor.clear.cgColor
        let viewFrame = self.frame
        for edge in edges {
            let gradientLayer = CAGradientLayer()
            gradientLayer.colors = [fromColor, toColor]
            gradientLayer.opacity = opacity

            switch edge {
            case .top:
                gradientLayer.startPoint = CGPoint(x: 0.5, y: 0.0)
                gradientLayer.endPoint = CGPoint(x: 0.5, y: 1.0)
                gradientLayer.frame = CGRect(x: 0.0, y: 0.0, width: viewFrame.width, height: radius)
            case .bottom:
                gradientLayer.startPoint = CGPoint(x: 0.5, y: 1.0)
                gradientLayer.endPoint = CGPoint(x: 0.5, y: 0.0)
                gradientLayer.frame = CGRect(x: 0.0, y: viewFrame.height - radius, width: viewFrame.width, height: radius)
            case .left:
                gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
                gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)
                gradientLayer.frame = CGRect(x: 0.0, y: 0.0, width: radius, height: viewFrame.height)
            case .right:
                gradientLayer.startPoint = CGPoint(x: 1.0, y: 0.5)
                gradientLayer.endPoint = CGPoint(x: 0.0, y: 0.5)
                gradientLayer.frame = CGRect(x: viewFrame.width - radius, y: 0.0, width: radius, height: viewFrame.height)
            default:
                break
            }
            self.layer.addSublayer(gradientLayer)
        }
    }

    func removeAllShadows() {
        if let sublayers = self.layer.sublayers, !sublayers.isEmpty {
            for sublayer in sublayers {
                sublayer.removeFromSuperlayer()
            }
        }
    }
}

顶视图为默认设置，底部使用半径5.0显示更清晰。

view1.addShadow([.top, .bottom, .left, .right])
view2.addShadow([.top, .bottom, .left, .right], radius: 5.0)
view2.backgroundColor = .orange

Answer 4

这是我制作的纯 Swift 版本：

public class EdgeShadowLayer: CAGradientLayer {

    public enum Edge {
        case Top
        case Left
        case Bottom
        case Right
    }

    public init(forView view: UIView,
                edge: Edge = Edge.Top,
                shadowRadius radius: CGFloat = 20.0,
                toColor: UIColor = UIColor.white,
                fromColor: UIColor = UIColor.black) {
        super.init()
        self.colors = [fromColor.cgColor, toColor.cgColor]
        self.shadowRadius = radius

        let viewFrame = view.frame

        switch edge {
            case .Top:
                startPoint = CGPoint(x: 0.5, y: 0.0)
                endPoint = CGPoint(x: 0.5, y: 1.0)
                self.frame = CGRect(x: 0.0, y: 0.0, width: viewFrame.width, height: shadowRadius)
            case .Bottom:
                startPoint = CGPoint(x: 0.5, y: 1.0)
                endPoint = CGPoint(x: 0.5, y: 0.0)
                self.frame = CGRect(x: 0.0, y: viewFrame.height - shadowRadius, width: viewFrame.width, height: shadowRadius)
            case .Left:
                startPoint = CGPoint(x: 0.0, y: 0.5)
                endPoint = CGPoint(x: 1.0, y: 0.5)
                self.frame = CGRect(x: 0.0, y: 0.0, width: shadowRadius, height: viewFrame.height)
            case .Right:
                startPoint = CGPoint(x: 1.0, y: 0.5)
                endPoint = CGPoint(x: 0.0, y: 0.5)
                self.frame = CGRect(x: viewFrame.width - shadowRadius, y: 0.0, width: shadowRadius, height: viewFrame.height)
        }
    }

    required public init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }   
}

要使用它，

let topShadow = EdgeShadowLayer(forView: targetView, edge: .Top)
targetView.layer.addSublayer(topShadow)

请注意，它默认为 20 点深的黑白渐变。

可以在https://github.com/jrtibbetts/Tenebrae 找到完整的代码，其中包含一个示例UIViewController，可让您在视图的所有四个角上切换阴影。我还非常彻底地记录了EdgeShadowLayer。

Answer 5

我更新了@NRitH 的答案并对其进行了扩展，也对其进行了修改，以便您可以一次操作多个边缘

用法

myview.addShadow(to: [.top,.bottom], radius: 15.0)

extension UIView{

    func addShadow(to edges:[UIRectEdge], radius:CGFloat){

        let toColor = UIColor(colorLiteralRed: 235.0/255.0, green: 235.0/255.0, blue: 235.0/255.0, alpha: 1.0)
        let fromColor = UIColor(colorLiteralRed: 188.0/255.0, green: 188.0/255.0, blue: 188.0/255.0, alpha: 1.0)
        // Set up its frame.
        let viewFrame = self.frame
        for edge in edges{
            let gradientlayer          = CAGradientLayer()
            gradientlayer.colors       = [fromColor.cgColor,toColor.cgColor]
            gradientlayer.shadowRadius = radius

            switch edge {
            case UIRectEdge.top:
                gradientlayer.startPoint = CGPoint(x: 0.5, y: 0.0)
                gradientlayer.endPoint = CGPoint(x: 0.5, y: 1.0)
                gradientlayer.frame = CGRect(x: 0.0, y: 0.0, width: viewFrame.width, height: gradientlayer.shadowRadius)
            case UIRectEdge.bottom:
                gradientlayer.startPoint = CGPoint(x: 0.5, y: 1.0)
                gradientlayer.endPoint = CGPoint(x: 0.5, y: 0.0)
                gradientlayer.frame = CGRect(x: 0.0, y: viewFrame.height - gradientlayer.shadowRadius, width: viewFrame.width, height: gradientlayer.shadowRadius)
            case UIRectEdge.left:
                gradientlayer.startPoint = CGPoint(x: 0.0, y: 0.5)
                gradientlayer.endPoint = CGPoint(x: 1.0, y: 0.5)
                gradientlayer.frame = CGRect(x: 0.0, y: 0.0, width: gradientlayer.shadowRadius, height: viewFrame.height)
            case UIRectEdge.right:
                gradientlayer.startPoint = CGPoint(x: 1.0, y: 0.5)
                gradientlayer.endPoint = CGPoint(x: 0.0, y: 0.5)
                gradientlayer.frame = CGRect(x: viewFrame.width - gradientlayer.shadowRadius, y: 0.0, width: gradientlayer.shadowRadius, height: viewFrame.height)
            default:
                break
            }
            self.layer.addSublayer(gradientlayer)
        }

    }

    func removeAllSublayers(){
        if let sublayers = self.layer.sublayers, !sublayers.isEmpty{
            for sublayer in sublayers{
                sublayer.removeFromSuperlayer()
            }
        }
    }

}

Answer 6

我在 Swift 3 上重写了@NRitH 解决方案，也稍微重构了它：

final class SideShadowLayer: CAGradientLayer {
    enum Side {
        case top,
        bottom,
        left,
        right
    }

    init(frame: CGRect, side: Side, shadowWidth: CGFloat,
         fromColor: UIColor = .black,
         toColor: UIColor = UIColor(red: 0, green: 0, blue: 0, alpha: 0),
         opacity: Float = 0.5) {
        super.init()

        colors = [fromColor.cgColor, toColor.cgColor]
        self.opacity = opacity

        switch side {
        case .bottom:
            startPoint = CGPoint(x: 0.5, y: 1.0)
            endPoint = CGPoint(x: 0.5, y: 0.0)
            self.frame = CGRect(x: 0, y: frame.height - shadowWidth, width: frame.width, height: shadowWidth)

        case .top:
            startPoint = CGPoint(x: 0.5, y: 0.0)
            endPoint = CGPoint(x: 0.5, y: 1.0)
            self.frame = CGRect(x: 0, y: 0, width: frame.width, height: shadowWidth)

        case .left:
            startPoint = CGPoint(x: 0.0, y: 0.5)
            endPoint = CGPoint(x: 1.0, y: 0.5)
            self.frame = CGRect(x: 0, y: 0, width: shadowWidth, height: frame.height)

        case .right:
            startPoint = CGPoint(x: 1.0, y: 0.5)
            endPoint = CGPoint(x: 0.0, y: 0.5)
            self.frame = CGRect(x: frame.width - shadowWidth, y: 0, width: shadowWidth, height: frame.height)
        }
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
}

Answer 7

我使用 Objective-C 实现 UIView 的内部阴影。我尝试将代码翻译成 swift。请原谅我糟糕的 swift 语法

你可以在 UIView.didMoveToSuperview 中调用下面的函数

func drawShadow() {
    if nil == self.shadowLayer {
        let size = self.frame.size
        self.clipsToBounds = true
        let layer: CALayer = CALayer()
        layer.backgroundColor = UIColor.lightGrayColor().CGColor
        layer.position = CGPointMake(size.width / 2, -size.height / 2 + 0.5)
        layer.bounds = CGRectMake(0, 0, size.width, size.height)
        layer.shadowColor = UIColor.darkGrayColor().CGColor
        layer.shadowOffset = CGSizeMake(0.5, 0.5)
        layer.shadowOpacity = 0.8
        layer.shadowRadius = 5.0
        self.shadowLayer = layer

        self.layer.addSublayer(layer)
    }
}