Question

我试图在使用键盘显示时将文本字段上移，而在隐藏键盘时又将文本字段下移。因此，我在使用NotificationCenter.default.addObserver，但这仅在充电时有效，而当我从充电器中取出时却不起作用，也就是说，它可能无法移动。请帮我解决这个问题。预先感谢

下面是我的代码：

 override func viewDidLoad() {
    super.viewDidLoad()

    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
  }

   @objc func keyboardWillShow(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y != 0{
            self.view.frame.origin.y -= 50
        }
    }
}

@objc func keyboardWillHide(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y != 0{
            self.view.frame.origin.y += 50
        }
    }
}

Answer 1

问题是您使用的是UIKeyboardFrameBeginUserInfoKey而不是UIKeyboardFrameEndUserInfoKey。

代码应为：

@objc func keyboardWillShow(_ notification: Notification) {
    if let keyboardFrame: NSValue = notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue {
        let keyboardRectangle = keyboardFrame.cgRectValue
        let keyboardHeight = keyboardRectangle.height
    }
}

Answer 2

如果self.view.frame.origin.y是0，则什么也没有发生。是吗？

@objc func keyboardWillShow(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        // If `origin.y` is `0`, then do nothing.
        if self.view.frame.origin.y != 0{
            self.view.frame.origin.y -= 50
        }
    }

@objc func keyboardWillHide(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        // If `origin.y` is `0` in `keyboardWillShow`, 
        // it will still be `0` here.
        // So, do nothing. 
        if self.view.frame.origin.y != 0{
            self.view.frame.origin.y += 50
        }
    }
}

NotificationCenter默认的addObserver仅在充电时起作用吗？

2 个答案: