为什么我的 UILongPressGestureRecognizer 不工作？

Question

我有以下代码，但我的长按没有按应有的方式工作。有人能弄清楚为什么它不起作用吗？

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    let longPressRecognizer = UILongPressGestureRecognizer(target: self, action: "myButton:")
    longPressRecognizer.minimumPressDuration = 0.5
    myButton.addGestureRecognizer(longPressRecognizer)
}

@IBOutlet weak var myButton: UIButton!

@IBAction func myButton(longPress: UILongPressGestureRecognizer) {

    if longPress.state != .Began {

        presentAlertController()

        return
    }
}

当我按住按钮

时出现此错误

2016-01-09 00:41:28.785 longPressTest[1870:551106] Warning: Attempt to present <UIAlertController: 0x144d6a500>  on <longPressTest.ViewController: 0x144e3a450> which is already presenting <UIAlertController: 0x144e59d80>
2016-01-09 00:41:28.903 longPressTest[1870:551106] Attempting to load the view of a view controller while it is deallocating is not allowed and may result in undefined behavior (<UIAlertController: 0x144d6a500>)
2016-01-09 00:41:28.905 longPressTest[1870:551106] Warning: Attempt to present <UIAlertController: 0x144e54bb0>  on <longPressTest.ViewController: 0x144e3a450> which is already presenting <UIAlertController: 0x144e59d80>
Cancel

Answer 1

长按手势是连续手势。这意味着识别器将在检测到使用 state == .Began 开始长按（0.5 秒后）时调用您的函数 (myButton(_:))，并随着触摸在屏幕上的移动而重复使用 [=13] =]，当手势以 state == .Ended 结束时再次出现。您尝试在每个 .Changed 调用和 .Ended 调用中显示警报，但当您尝试显示已经显示的警报时出现错误。

如果您想在 0.5 秒后立即显示警报，请在状态为 .Began 时执行，而不是在状态为任何状态时执行 except .Began.

@IBAction func myButton(longPress: UILongPressGestureRecognizer) {
    if longPress.state == .Began {
        presentAlertController()
    }
}

您只会接到一个状态为 .Began 的电话，因此您不会在警报已经显示时再次尝试显示它。

为什么我的 UILongPressGestureRecognizer 不工作？

Why isn't my UILongPressGestureRecognizer working?

uigesturerecognizer

ios

swift