Ios 使用自定义键盘时获得正确的键盘高度值-SWIFT 3

因此，我有一个UIButton，它位于UIView的底部，直到键盘出现，然后底部约束更新为键盘高度

这适用于iOS默认键盘，但当使用自定义键盘（如快捷键）时，底部约束仍然是iOS键盘高度的约束

我注意到一个自定义键盘会触发三个通知，而不是一个。这可能是个问题，但我如何使用正确的值呢

@IBOutlet weak var fieldBottomConstant: NSLayoutConstraint!

var keyboardShowing = false

var keyboardHeight: CGFloat = 0.0

func keyboardWillShow(_ n:Notification) {

    self.keyboardShowing = true

    if let keyboardSize = (n.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
       // fieldBottomConstant.constant = keyboardSize.height
       keyboardHeight = keyboardSize.height
    }

    fieldBottomConstant.constant = keyboardHeight

}

func keyboardWillHide(_ n:Notification) {

    self.keyboardShowing = false

    fieldBottomConstant.constant = 0

}


override func viewWillAppear(_ animated: Bool) {
    NotificationCenter.default.addObserver(self, selector: #selector(AddViewController.keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(AddViewController.keyboardWillHide(_:)), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(AddViewController.keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(AddViewController.keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardDidShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(AddViewController.keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardDidChangeFrame, object: nil)

}

更新

我添加了更多的通知以观察任何更改，旋转设备后，约束将更改为自定义键盘高度，但在首次加载键盘时仍不使用自定义键盘高度。

您应该收听NSNotification.Name.UIKeyboardWillChangeFrame

答案是使用

UIKeyboardFrameEndUserInfoKey