title: Get UITextField from Keyboard Notifications
body: <p>I am trying to get <code>UITextField</code> that on which the observer <code>UIKeyboardDidShowNotification</code> is being called. </p>
  
  <p>My Observer is in <code>appdelegate</code> and I have several UIViewControllers that have several UITextFields in them, in short I don't know current First Responder. </p>
  
  <p>How can I get the first responder inside my Method that is fired upon the keyboard notification <code>UIKeyboardDidShowNotification</code>?</p>