title: UIKeyboardWillShowNotification selector not called but HideNotification is called
body: <p>I have added observers so that I can move textFields above keyboard.
  Its working fine on all devices but <code>keyboardWillAppear</code> function is not called when running in simulator iPhone 4S (iOS 9).
  This is happening when I "Connect Hardware Keyboard"</p>
  
  <p><code>keyboardWillHide</code> is being called instead of <code>keyboardWillShow</code></p>
  
  <p><a href="https://i.stack.imgur.com/d0niK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/d0niK.png" alt="keyboard"></a></p>
  
  <pre><code>override func viewDidLoad() {
    super.viewDidLoad()
  
    NSNotificationCenter.defaultCenter().addObserver(self, selector:"keyboardWillAppear:", name: UIKeyboardWillShowNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector:"keyboardWillDisappear:", name: UIKeyboardWillHideNotification, object: nil)
  }
  
  
  func keyboardWillAppear(notification: NSNotification){
    // This is not called on simulator iPhone 4S(iOS 9.0)
  }
  
  func keyboardWillDisappear(notification: NSNotification){
    // This is called
  }
  </code></pre>
  
  <p>I really can't understand this behaviour. Can someone please explain the internal functionality which leads to this.</p>