Question

我试图用 UITextField 和 UIButton 制作一个 UIView - 就像聊天应用程序一样。

我想检测出现在屏幕上的键盘级别，并根据它改变UIView高度约束。

我该怎么做？

现在我有了这个

  @IBOutlet weak var messageTextField: UITextField!
    @IBOutlet weak var bottomBarConstrains: NSLayoutConstraint!

    override func viewDidLoad()
    {
        super.viewDidLoad()

        NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillShow:"), name:UIKeyboardWillShowNotification, object: nil);
        NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillHide:"), name:UIKeyboardWillHideNotification, object: nil);

    }

    override func didReceiveMemoryWarning()
    {
        super.didReceiveMemoryWarning()
    }

    @IBAction func sendAction(sender: AnyObject)
    {
        messageTextField.resignFirstResponder();
    }

    func keyboardWillShow(notification: NSNotification)
    {
        var info = notification.userInfo!
        let keyboardFrame: CGRect = (info[UIKeyboardFrameEndUserInfoKey] as! NSValue).CGRectValue()
        let duration = info[UIKeyboardAnimationDurationUserInfoKey] as! Double

        UIView.animateWithDuration(duration, delay: 2, options: UIViewAnimationOptions.CurveEaseIn, animations:
            { () -> Void in
                self.bottomBarConstrains.constant = keyboardFrame.size.height;
            },
            completion: nil);
    }

    func keyboardWillHide(notification: NSNotification)
    {
        var info = notification.userInfo!
        let duration = info[UIKeyboardAnimationDurationUserInfoKey] as! Double

        UIView.animateWithDuration(duration, animations: { () -> Void in
            self.bottomBarConstrains.constant = 0;
        })
    }

但它没有动画

Answer 1

如果要为更改的约束设置动画，则需要在使用该约束的视图上使用layoutIfNeeded方法。此方法强制视图更改布局子视图，但仅在需要时才更改。由于约束更改不会自动强制更改视图位置，因此需要调用此方法。因此，如果您的messageTextView是self.view的子视图，请使用：

self.bottomBarConstrains.constant = keyboardFrame.size.height

UIView.animateWithDuration(duration, delay: 2, options: .CurveEaseIn, animations: {
     self.view.layoutIfNeeded()
}, completion: nil);

Answer 2

更改KeyBoard打开和隐藏的代码，如下所示，打开KeyBoard时删除延迟，

func keyboardWillShow(notification: NSNotification)
    {

        var info = notification.userInfo!
        let keyboardFrame: CGRect = (info[UIKeyboardFrameEndUserInfoKey] as! NSValue).CGRectValue()
        let duration = info[UIKeyboardAnimationDurationUserInfoKey] as! Double
        self.bottomBarConstrains.constant = keyboardFrame.size.height

        UIView.animateWithDuration(duration, animations: { () -> Void in

            self.messageTextField.layoutIfNeeded()
            self.view.layoutIfNeeded()
        })
    }

    func keyboardWillHide(notification: NSNotification)
    {
        var info = notification.userInfo!
        let duration = info[UIKeyboardAnimationDurationUserInfoKey] as! Double
        self.bottomBarConstrains.constant = 0;

        UIView.animateWithDuration(duration, animations: { () -> Void in

            self.messageTextField.layoutIfNeeded()
            self.view.layoutIfNeeded()
        })
    }

输出：

键盘出现动作

2 个答案: