On iOS we may need relayout our app when keyboard was shown. To handle it, we can observer below four notifications to know when the keyboard is shown or hidden.
UIKeyboardWillShowNotification
UIKeyboardDidShowNotification
UIKeyboardWillHideNotification
UIKeyboardDidHideNotification
But we should know the keyboard related notifications are not always posted. UIKeyboardWillShowNotification/UIKeyboardDidShowNotification only be posted when the keyboard is changed, including the keyboard visibility and keyboard size change. For example:
- Keyboard is displayed and before is not visible, you can get
UIKeyboardWillShowNotification/UIKeyboardDidShowNotification - Keyboard size is changed, UITextField doesn’t have customized toolbar on keyboard, but UITextView has one, so change focus between UITextField and UITextView, you can get
UIKeyboardWillShowNotification/UIKeyboardDidShowNotification - Otherwise, you cannot get
UIKeyboardWillShowNotification/UIKeyboardDidShowNotification. For example you change focus between UITextField, or UITextView. Because the keyboard size is not changed.
Further step, the keyboard So if you change the focus from one UITextField/UITextView to another one, you cannot get he UIKeyboardWillShowNotification/UIKeyboardDidShowNotification. To support the focus changes between text view, we should track the text view.