title: How to resize view according to keyboard show/hide if keyboard is already shown
body: <p>In view A, I have a text field. I tap a control to push in a new view controller B. View B only has a text view whose frame should be adjusted to accommodate the keyboard, and I always set the text view to be the first responder and the keyboard should show immediately when view B is pushed in.</p>
  
  <p>I do the usual keyboard notification handling in view controller B. So if the keyboard is not shown before view B is pushed, there is no problem. However, if the text field in view A is the first responder and the keyboard is already shown when I push in view controller B, I won't receive UIKeyboardWillShowNotification/UIKeyboardDidShowNotification. Any suggestion to handle this situation?</p>