Swift UIView阴影不可见

我有一个名为

containerView

的

ui视图

创建UIView并将其添加到主视图后，我尝试添加一点阴影。我的代码：

    let containerView = UIView()

    let bg_clear = UIColor(hexString: "#34495E")
    containerView.backgroundColor = bg_clear


    containerView.layer.cornerRadius =  15
    containerView.clipsToBounds = false

    containerView.dropShadow() // Generate Shadow

    view.addSubview(containerView)

    containerView.translatesAutoresizingMaskIntoConstraints = false
    containerView.heightAnchor.constraint(equalToConstant: 50).isActive = true
    containerView.widthAnchor.constraint(equalToConstant: 300).isActive = true
    containerView.centerXAnchor.constraint(equalTo: tabBar.centerXAnchor).isActive = true

生成阴影的代码：

extension UIView {

    func dropShadow(scale: Bool = true) {
        layer.masksToBounds = false
        layer.shadowColor = UIColor(hexString: "#000000").cgColor
        layer.shadowOpacity = 0.5
        layer.shadowOffset = CGSize(width: -1, height: 1)
        layer.shadowRadius = 1

        layer.shadowPath = UIBezierPath(rect: bounds).cgPath
        layer.shouldRasterize = true
        layer.rasterizationScale = scale ? UIScreen.main.scale : 1
   }
}

这将有助于：

extension UIView {

    func addShadow(withOpacity opacity:Float, radius:CGFloat, andColor color:UIColor) {
         self.layer.shadowColor         = color.cgColor
         self.layer.shadowOffset        = CGSize(width:-1.0, height:1.0)
         self.layer.shadowOpacity       = opacity
         self.layer.shadowRadius        = radius
    }
}

例如：

containerView.addShadow(withOpacity: 0.4, radius: 0.4, andColor: .black)

需要注意的几点：


确保容器视图不太靠近屏幕的左侧或底部，因为阴影将显示在容器视图的左侧和下方

确保阴影路径使用圆角矩形，因为容器视图的角半径非零

如果仍然看不到阴影，请尝试增加阴影偏移


您可以将此代码复制并粘贴到游乐场中，然后打开live view：

extension UIView {

    func dropShadow(scale: Bool = true) {
        layer.masksToBounds = false
        layer.shadowColor = UIColor.black.cgColor
        layer.shadowOpacity = 0.5
        layer.shadowOffset = CGSize(width: -5, height: 5) // I made this larger
        layer.shadowRadius = 1

        // I used a rounded rect here
        layer.shadowPath = UIBezierPath(roundedRect: self.bounds, cornerRadius: self.layer.cornerRadius).cgPath
        layer.shouldRasterize = true
        layer.rasterizationScale = scale ? UIScreen.main.scale : 1
    }
}

let view = UIView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
view.backgroundColor = .white
let containerView = UIView(frame: CGRect(x: 10, y: 10, width: 100, height: 100))

let bg_clear = UIColor.green
containerView.backgroundColor = bg_clear


containerView.layer.cornerRadius =  15
containerView.clipsToBounds = false

containerView.dropShadow() // Generate Shadow

view.addSubview(containerView)

PlaygroundPage.current.liveView = view

你应该看到：