iOS UIView添加陰影 四周和單個方向以及百分比

UIBezierPath

通常情況下設置陰影只需要設置layer就行，但是如果只是單邊陰影以及百分比，只設置layer效果不是多好，可以用貝塞爾曲線實現。

效果圖：

class ViewController: UIViewController {
    @IBAction func typeChange(_ sender: UISegmentedControl) {
        let myView = view.viewWithTag(10000)
        myView?.shadow(UIView.ShadowType(rawValue: sender.selectedSegmentIndex)!)
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        let itemView = UIView.init(frame: CGRect.init(x: 100, y: 120, width: 100, height: 100))
        itemView.backgroundColor = .red
        itemView.shadow(.all)
        itemView.tag = 10000
        view.addSubview(itemView)
    }


}


extension UIView {
    enum ShadowType: Int {
        case all = 0 ///四周
        case top  = 1 ///上方
        case left = 2///左邊
        case right = 3///右邊
        case bottom = 4///下方
    }
    ///默認設置：黑色陰影, 陰影所佔視圖的比例
   // func shadow(_ type: ShadowType, percent: Float) {
       // shadow(type: type, color: .black, opactiy: 0.4, //shadowSize: 4)
    //}
    ///默認設置：黑色陰影
    func shadow(_ type: ShadowType) {
        shadow(type: type, color: .black, opactiy: 0.4, shadowSize: 4)
    }
    ///常規設置
    func shadow(type: ShadowType, color: UIColor,  opactiy: Float, shadowSize: CGFloat) -> Void {
        layer.masksToBounds = false;//必須要等於NO否則會把陰影切割隱藏掉
        layer.shadowColor = color.cgColor;// 陰影顏色
        layer.shadowOpacity = opactiy;// 陰影透明度，默認0
        layer.shadowOffset = .zero;//shadowOffset陰影偏移，默認(0, -3),這個跟shadowRadius配合使用
        layer.shadowRadius = 3 //陰影半徑，默認3
        var shadowRect: CGRect?
        switch type {
        case .all:
            shadowRect = CGRect.init(x: -shadowSize, y: -shadowSize, width: bounds.size.width + 2 * shadowSize, height: bounds.size.height + 2 * shadowSize)
        case .top:
            shadowRect = CGRect.init(x: -shadowSize, y: -shadowSize, width: bounds.size.width + 2 * shadowSize, height: 2 * shadowSize)
        case .bottom:
            shadowRect = CGRect.init(x: -shadowSize, y: bounds.size.height - shadowSize, width: bounds.size.width + 2 * shadowSize, height: 2 * shadowSize)
        case .left:
            shadowRect = CGRect.init(x: -shadowSize, y: -shadowSize, width: 2 * shadowSize, height: bounds.size.height + 2 * shadowSize)
        case .right:
            shadowRect = CGRect.init(x: bounds.size.width - shadowSize, y: -shadowSize, width: 2 * shadowSize, height: bounds.size.height + 2 * shadowSize)
        }
        layer.shadowPath = UIBezierPath.init(rect: shadowRect!).cgPath
    }
    
    
}