在Swift 4中创建类似Spotlight的窗口？

class SpotlightWindow: UIWindow {
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        // 在这里进行窗口的初始化设置
        self.windowLevel = UIWindow.Level.statusBar + 1
        self.backgroundColor = UIColor.clear
        self.isHidden = false
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

let spotlightWindow = SpotlightWindow(frame: UIScreen.main.bounds)
UIApplication.shared.delegate?.window??.addSubview(spotlightWindow)
UIApplication.shared.delegate?.window??.bringSubviewToFront(spotlightWindow)

class SpotlightWindow: UIWindow {
    // ...
    
    func showSpotlight(at point: CGPoint) {
        let spotlightView = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
        spotlightView.center = point
        spotlightView.backgroundColor = UIColor.black
        spotlightView.layer.cornerRadius = 50
        spotlightView.alpha = 0.5
        self.addSubview(spotlightView)
        
        UIView.animate(withDuration: 0.3, animations: {
            spotlightView.transform = CGAffineTransform(scaleX: 2, y: 2)
            spotlightView.alpha = 0
        }) { (_) in
            spotlightView.removeFromSuperview()
        }
    }
}