键盘高度被称为

Question

所以我有以下代码：

//MARK: - Textfield delegate Methods 

    func textFieldDidBeginEditing(textField: UITextField) 
    { 

     // update view based on updates in the constraints 
     self.view.layoutIfNeeded() 
     //perform animation to grow the dockview 
     UIView.animateWithDuration(0.5, animations: {() -> Void in 
      self.dockViewHeightConstraint.constant = self.keyBoardHeight + 60 
      self.view.layoutIfNeeded() 
      }, completion: nil) 
    } 

和

override func viewDidLoad() { 
    super.viewDidLoad() 
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillShow:", name: UIKeyboardWillShowNotification, object: nil)   
} 


func keyboardWillShow(notification: NSNotification) { 
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() { 
     let contentInsets = UIEdgeInsets(top: 0, left: 0, bottom: keyboardSize.height, right: 0) 
     keyBoardHeight = contentInsets.bottom 
    } 
} 

我所试图做的是以下几点。当用户点击文本框时，键盘应该打开，并且我所做的视图应该向上移动。 我从由NSNotification触发的keyboardWillShow函数获得键盘的高度。

问题是：当我运行代码时，在NSNotification之前调用textFieldDidBeginEditing，使self.keyBoardHeight值为0（初始值）。在按下textField之前，我可以调用NSNotification部件吗？

Answer 1

建立一个isKeyboardShown标志在你的viewController跟踪键盘是否显示与否，这与你的元素“myElement”相交可以fieldMovement财产被捕捉为以下

if !isKeyboardShown 
      { 
       if let info = notification.userInfo 
       { 
        if fieldMovement == nil 
        { 
         let window = UIApplication.sharedApplication().keyWindow 
         var keyboardEndRect = CGRectZero 

         //Get frame of keyboard view object 
         ((info[UIKeyboardFrameEndUserInfoKey] as! NSValue)).getValue(&keyboardEndRect) 

         /* Convert the frame from the window's coordinate system to our view's coordinate system */ 
         keyboardEndRect = view.convertRect(keyboardEndRect, fromView: window) 

         /* Find out how much of our view is being covered by the keyboard */ 
         fieldMovement = CGRectIntersection(myElement.frame, keyboardEndRect).height 
        } 

        //Get animation duration of keyboard 
        var animationDuration: NSTimeInterval = 0 
        (info[UIKeyboardAnimationDurationUserInfoKey] as! NSValue).getValue(&animationDuration) 

        // Move views up by intersected height 
       UIView.animateWithDuration(animationDuration) 
       { 
        //animate your objects here 
       } 
      } 
      isKeyboardShown = true 
     }