未调用手势识别器

Question

我设置了一个手势识别器，用于在用户在文本字段外点击时关闭键盘。 DismissKeyboard 函数没有被调用。

我是否设置了错误的观察者或者这是一个不同的问题？另外，这是一个正在被点击的 tableview。

代码摘录

class CommentsViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        NSNotificationCenter.defaultCenter().addObserver(self,
            selector: Selector("keyboardWillShow:"),
            name: UIKeyboardWillShowNotification,
            object: nil)
        NSNotificationCenter.defaultCenter().addObserver(self,
            selector: Selector("keyboardWillHide:"),
            name: UIKeyboardWillHideNotification,
            object: nil)
    }

    func keyboardFrameChanged(notification: NSNotification) {
        println("keyboardFrameChanged")
        let userInfo = notification.userInfo
        let key = UIKeyboardFrameEndUserInfoKey
        if let info = userInfo {
            let frameValue = info[key] as! NSValue
            let _frame = frameValue.CGRectValue()
        }
    }
    
    func keyboardWillShow(notification: NSNotification) {
        if keyboardDismissTapGesture == nil
        {
            println("dismiss")
            keyboardDismissTapGesture = UITapGestureRecognizer(target: self, action: Selector("dismissKeyboard:"))
            self.view.addGestureRecognizer(keyboardDismissTapGesture!)
        }
    }
    
    func keyboardWillHide(notification: NSNotification) {
        if keyboardDismissTapGesture != nil
        {
            println("test2")
            self.view.removeGestureRecognizer(keyboardDismissTapGesture!)
            keyboardDismissTapGesture = nil
        }
    }
    
    func dismissKeyboard(sender: AnyObject) {
        println("dismiss keyboard")
        commentTextField.resignFirstResponder()
    }

我在dismissKeyboard 处设置了一个断点，但它甚至没有被调用。

输出

当我点击文本视图并打开键盘时，这是输出

keyboardFrameChanged
keyboardFrameChanged
will show
dismiss

当我点击其他任何东西（试图关闭键盘）时，没有进一步的输出。

Answer 1

为自己设置手势识别器委托并添加UIGestureRecognizerDelegate 协议。

func keyboardWillShow(notification: NSNotification) {
    if keyboardDismissTapGesture == nil
    {
        println("dismiss")
        keyboardDismissTapGesture = UITapGestureRecognizer(target: view, action: "dismissKeyboard:")
        keyboardDismissTapGesture.delegate = self
        self.view.addGestureRecognizer(keyboardDismissTapGesture!)
    }
}

然后添加：

func gestureRecognizer(gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWithGestureRecognizer otherGestureRecognizer: UIGestureRecognizer) -> Bool { 
    return true 
}

我的猜测是，您的表格视图的手势干扰了新的UITapGesture。试试这个解决方案，否则当检测到新的UITapGesture 时，表格视图的手势会失败。

要使表格视图的UITapGestureRecognizer 失败，我使用以下代码：

if let recognizers = yourTableView.gestureRecognizers, let index = find(recognizers.map { $0 is UITapGestureRecognizer }, true) {
    (recognizers[index] as! UIPanGestureRecognizer).requireGestureRecognizerToFail(keyboardDismissTapGesture)
}

也许不是最优雅的方式，但当我想失败 UIPanGestureRecognizer 时，它对我有用。我没有用UITapGestureRecognizer 测试过。

编辑：

if let recognizers = yourTableView.gestureRecognizers, let index = find(recognizers.map { $0 is UIGestureRecognizer }, true) {
    (recognizers[index] as! UIGestureRecognizer).requireGestureRecognizerToFail(keyboardDismissTapGesture!)
}