Question

我有以下代码，我的长按不按预期方式工作。任何人都可以找出它无法正常工作的原因吗？

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

时会出现此错误

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。这意味着识别器会在myButton(_:)检测到长按开始（0.5秒后）时调用您的函数（state == .Began），并且当触摸在{{1当手势以state == .Changed结束时再次出现。您尝试在每次state == .Ended来电和.Changed来电时都会显示提醒，当您尝试提示已经提供的提醒时，您会收到错误。

如果您希望在0.5秒后立即显示提醒，请在状态为.Ended时显示，而不是状态为除 .Began时。

.Began

您只能通过状态@IBAction func myButton(longPress: UILongPressGestureRecognizer) { if longPress.state == .Began { presentAlertController() } }拨打一个电话，这样您就不会尝试再次显示警报。

为什么我的UILongPressGestureRecognizer不起作用？

1 个答案: