调用文本字段委托之前所需的键盘高度

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
    }
}

我想要做的是以下。当用户单击文本字段时，键盘应该打开，并且我制作的视图应该向上移动。 我通过 NSNotification 触发的keyboardWillShow 函数从键盘获取高度。

问题如下：当我运行代码时，textFieldDidBeginEditing 在 NSNotification 之前被调用，使我的 self.keyBoardHeight 值为 0（初始值）。有没有办法在按下 textField 之前调用 NSNotification 部分？

Answer 1

在 viewController 中设置 isKeyboardShown 标志来跟踪是否显示键盘，与元素“myElement”相交的高度可以在 fieldMovement 属性中捕获，如下所示

    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
        }