在键盘上方显示UIView无法正常工作

Question

我正在尝试将约束移到底部。UI视图的常量，其中我的UITextField显示后位于键盘上方。我设置了通知观察器，但由于某种原因，它不起作用。

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)
        })
    }
}

当我打印constraintToBottom时。常量显示：

常数346.0

然而，像往常一样，在键盘上方仍然看不到UIView。我做错了什么？

更新

正如所建议的，负号起作用，但也有额外的空间，它看起来是这样的：




Answer 1

你需要重新布局视图

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