title: How to detect user interactions on a whole viewcontroller
body: <p>I would like to detect the user interactions on a UIViewController like</p>
  
  <ol>
  <li>Editing Text Fields</li>
  <li>Selecting picture from gallery</li>
  <li>Picker view selections</li>
  </ol>
  
  <p>Its indented to show a notification like "You may lose data you have entered" when user goes out of page. Can be back button. </p>
  
  <p>Have seen many answers but i need the best and proper way of doing this functionality.</p>