NSNotificationCenter Swift 3.0 on keyboard show and hide

Question

I am trying to run a function when the keyboard shows and disappears and have the following code:

let notificationCenter = NotificationCenter.default
notific         


        

Answer 1

Swift 4.X / 5

I like the inline, block-based approach which is available for a long time already! You can read more about the parameters of addObserver(...) here.

Some advantages of this approach are:

• you don't need to use the @objc keyword
• you write your callback code at the same location where you setup your observer

Important: Call NotificationCenter.default.removeObserver(observer) in the deinit of the object where you set register the observer (often a view controller).

let center = NotificationCenter.default

let keyboardWillShowObserver: NSObjectProtocol = center.addObserver(forName: UIResponder.keyboardWillShowNotification, object: nil, queue: nil) { (notification) in
    guard let value = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue else { return }
    let height = value.cgRectValue.height

    // use the height of the keyboard to layout your UI so the prt currently in
    // foxus remains visible
}

let keyboardWillHideObserver: NSObjectProtocol = center.addObserver(forName: UIResponder.keyboardWillHideNotification, object: nil, queue: nil) { (notification) in

    // restore the layout of your UI before the keyboard has been shown
}