手勢識別器在時間後無響應

Question

我有一段時間後似乎無響應的UILongPressGestureRecognizer。它似乎與時間流逝相關，並且可能與失去活動狀態並進入背景的應用相關。

我經常遇到問題，當我第一次重新打開應用程序，並嘗試長按或刷卡，既沒有工作。如果我轉到不同的視圖控制器然後返回，那麼重新加載會導致手勢識別器再次開始工作！

let longpress = UILongPressGestureRecognizer(target: self, action: #selector(ViewController.longPressGestureRecognized(_:))) 
    mainView.addGestureRecognizer(longpress) 

圍繞處理手勢識別器變得沒有響應這樣的任何想法？

Answer 1

請嘗試以下方法。

1. 讓longpress一個全局變量
2. 在viewWillAppear添加手勢，如果它不存在
3. 在viewWillAppear添加通知UIApplicationWillEnterForeground
4. 中刪除手勢和通知viewWillDisappear

像這樣的東西

var longpress: UILongPressGestureRecognizer! 

override viewDidLoad() { 
    super.viewDidLoad 
    longpress = UILongPressGestureRecognizer(target: self, action: #selector(ViewController.longPressGestureRecognized(_:))) 
} 

override viewWillAppear(_ animated: Bool) { 
    super.viewWillAppear(animated) 
    checkGestureAvailability() 
    NotificationCenter.default.addObserver(self, selector: #selector(checkGestureAvailability), name: Notification.Name.UIApplicationWillEnterForeground, object: nil) 
} 

override viewWillDisappear(_ animated: Bool) { 
    if mainView.gestureRecognizers.contains(longpress) { 
     mainView.removeGestureRecognizer(longpress) 
    } 
    NotificationCenter.default.removeObserver(self, name: Notification.Name.UIApplicationWillEnterForeground, object: nil) 
    super.viewWillDisappear(animated) 
} 

func checkGestureAvailability() { 
    if !mainView.gestureRecognizers.contains(longpress) { 
     mainView.addGestureRecognizer(longpress) 
    } 
}