在键盘上方显示UIView不能正常工作

Question

我试图将constraintToBottom.constant的{​​{1}}移到键盘上显示的UIView所在的位置。我设置了UITextField观察者，但是由于某种原因，它不起作用。

Notification

当我打印override func viewDidLoad() { super.viewDidLoad() NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(_:)), name: UIResponder.keyboardWillShowNotification, object: nil) NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide(_:)), name: UIResponder.keyboardWillHideNotification, object: nil) } @objc func keyboardWillShow(_ notification: Notification) { if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue { UIView.animate(withDuration: 0.3, animations: { self.constraintToBottom.constant = keyboardSize.height print("constant", self.constraintToBottom.constant) }) } } 时，它显示：

  

常数346.0

但是，constraintToBottom.constant仍然像往常一样在键盘上方不可见。我在做什么错了？

更新

如建议的那样，减号可以解决问题，但是还有额外的空间，它看起来像这样：

Answer 1

您需要重新布局视图

self.constraintToBottom.constant = -1 * keyboardSize.height
UIView.animate(withDuration: 0.3, animations: {
     self.view.layoutIfNeeded()
     print("constant", self.constraintToBottom.constant)
})