如何取消 LongPressGestureRecognizer？

Question

我有一个分配了 LongPressGestureRecognizer 的视图，它调用以下方法：

@IBAction func longPressOnView1Recognized(_ sender: UIGestureRecognizer) {

    if sender.state == .began {
        // this runs when user's finger is down a "long time"
    }
    if sender.state == .ended {
        // this runs when user's finger goes up again after the .began state 
    }

}

这一切都按预期工作，但我正在尝试找到一种 (good/proper) 方式，能够以编程方式 cancel 长按识别器（在某些情况下），同时用户的手指还在下

也就是说，while用户的手指还在view上，识别器进入了.began状态，（但是before 用户已经抬起手指——在识别器进入 .ended 状态之前）...是否有一些代码我们可以运行来防止上述方法在用户抬起手指时触发...比如过早地告诉 IOS 在这个手势的剩余部分不再监听 UP 事件？

我读过这些 docs，但我对 IOS 触摸没有那么多经验，而且我似乎找不到任何为此目的而设计的方法。

我的 GestureRecognizer.reset() 似乎与我描述的不符。

我想到了两种可能：

1) 一个布尔标志，将进入 if sender.state == .ended {} 闭包

2) 这个：

myLongPressRecognizer.isEnabled = false
myLongPressRecognizer.isEnabled = true

这两个都有效，但似乎不太好。

Answer 1

您已经有了解决方案。切换 UILongPressGestureRecognizer isEnabled 是最好的方法。设置 state 属性是不可能的，因为它是一个 get-only 属性.

open var state: UIGestureRecognizer.State { get } // the current state of the gesture recognizer

isEnabled 属性记录为：

default is YES. disabled gesture recognizers will not receive touches. when changed to NO the gesture recognizer will be cancelled if it's currently recognizing a gesture.

Answer 2

你们都很擅长禁用和重新启用手势识别器

myLongPressRecognizer.isEnabled = false
myLongPressRecognizer.isEnabled = true

完全正确。

我担心的是你不完全理解手势识别器。在处理手势识别器时，您应该始终使用 switch 语句。查看评论：

func handleLongPressGestureRecognizer(_ sender: UIGestureRecognizer) {

    switch sender.state {
    case .began:
        // This will be called only once when the gesture starts
        print("Long press did begin at \(sender.location(in: sender.view))")
    case .changed:
        // This will be called whenever your finger moves (at some frequency obviously).
        // At this point your long press gesture is acting exactly the same as pan gesture
        print("Long press changed position to \(sender.location(in: sender.view))")
    case .ended:
        // This is when user lifts his finger assuming the gesture was not canceled
        print("Long press ended at \(sender.location(in: sender.view))")
    case .cancelled:
        // This is equally important as .ended case. You gesture may be canceled for many reasons like a system gesture overriding it. Make sure to implement logic here as well.
        print("Long press canceled at \(sender.location(in: sender.view))")
    case .failed, .possible:
        // These 2 have been added additionally at some point. Useless as far I am concerned.
        break
    }

}

所以至少你应该处理取消状态。但还要注意，只要移动手势，就会触发更改的状态。

Answer 3

您可以导入手势识别器header:

import UIKit.UIGestureRecognizer

这将使 state 属性成为读写属性。因此，要取消手势，只需将其 state 更改为 .cancelled.

因此，例如，您可以在识别长按手势识别器一秒后取消它，例如：

weak var timer: Timer?

@objc func handleLongPress(_ gesture: UILongPressGestureRecognizer) {
    switch gesture.state {
    case .began:
        print("began")
        timer?.invalidate()
        timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: false) { _ in
            gesture.state = .cancelled
        }

    case .ended, .cancelled:
        print(gesture.state == .ended ? "Ended" : "Cancelled")
        timer?.invalidate()

    default:
        break
    }
}

如何取消 LongPressGestureRecognizer？

How to cancel LongPressGestureRecognizer?

uigesturerecognizer

ios

swift