Swift 实现指尖触摸屏幕处的预览小窗口

最近在研究K线，以及画线工具，当手指触摸屏幕的时候，指尖的屏幕处看不到，被指尖挡住了，这样我拖动画线的锚点的时候，就不是很灵活准确。为此，做了个预览的功能。

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    if let touch = touches.first {
        let location = touch.location(in: self)
        let scale = UIScreen.main.scale
        let rect = CGRect(x: location.x - 50, y: location.y - 50, width: 100, height: 100)
        UIGraphicsBeginImageContextWithOptions(rect.size, false, scale)
        self.drawHierarchy(in: CGRect(origin: CGPoint(x: -rect.origin.x, y: -rect.origin.y), size: self.bounds.size), afterScreenUpdates: true)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        

        let imageView = UIImageView(image: image)
        imageView.frame = CGRect(x: 0, y: 0, width: 200, height: 200)
        imageView.contentMode = .scaleAspectFit
        let popup = UIView(frame: UIScreen.main.bounds)
        popup.backgroundColor = UIColor(white: 0, alpha: 0.5)
        popup.addSubview(imageView)
        self.view.addSubview(popup)
        }

}

效果图

IMG_1D21C5207006-1.jpeg