如何检测“长按”

Question

我有一个UIView视图，我想在用户按下然后释放时执行一些操作。 我在视图中添加了一个UITapGestureRecognizer ，它仅在点击持续时间很短时触发。 如果用户触摸视图，等待几秒钟然后抬起手指，则什么也不会发生。 如何检测“长按”事件？

UILongPressGestureRecognizer对我不起作用，因为当手指仍然触摸屏幕时它会触发。

Answer 1

您可以通过跟踪touchesBegan和touchesEnded的时间来做到这一点：

class LongTapView: UIView {
    
    var touchStart: Date!
    
    var callback: ((Double)->())?
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        touchStart = Date()
    }
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        guard let touchPoint = touches.first?.location(in: self),
              self.bounds.contains(touchPoint) else {
            // touch moved outside of self,
            //  so don't consider it "still pressed"
            touchStart = Date.distantFuture
            return
        }
    }
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        guard let touchPoint = touches.first?.location(in: self),
              self.bounds.contains(touchPoint) else {
            // touch was lifted outside of self
            return
        }
        let seconds = -(touchStart.timeIntervalSinceNow)
        if seconds < 0.0 {
            // this will be the case if touchesMoved outside of self
            //  and then was dragged back in
            return
        }
        // tell the controller how long the view was touched
        callback?(seconds)
    }
}

你可以像这样使用它：

class TouchTestViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let v = LongTapView()
        v.frame = CGRect(x: 80, y: 120, width: 150, height: 150)
        v.backgroundColor = .red
        view.addSubview(v)
        
        v.callback = { elapsedTime in
            // do what you want here, for example:
            if elapsedTime > 4.0 {
                print("View was pressed longer than 4 seconds!")
            } else {
                print("View was pressed for only \(elapsedTime) seconds")
            }
        }
        
    }
}