title: View on top of everything: UIWindow subview VS UIViewController subview
body: <p>In order to make a <code>UIView</code> on top of all views like the behavior of <code>UIAlertView</code>, the best way I see is by putting it in the app window, which is by adding the view to: </p>
  
  <pre><code>[[[UIApplication sharedApplication] delegate] window]
  </code></pre>
  
  <p>However, the downside I found is that it doesn't automatically take in rotation. In order for it to take in rotation, the best way to do is by adding the view on current AppDelegate <code>window.navigationController</code>/<code>rootViewController</code>, however, by doing this it will no longer be on top of everything. Let say when view is displaying and there is a modalViewController popup, the modal view will certainly cover up the view.</p>
  
  <p>My question is, is it possible to add subview to the top most window <em>and</em> support orientation? Do I need two set of Nib file in this case? How <code>UIAlertView</code> does the magic to combine the topmost &amp; orientation support? When I look into the <code>UIAlertView.h</code>, I see there is actually 2 <code>UIWindows</code>, once is called <code>originalWindow</code> and another called <code>dimWindow</code>. Is there a place where I can find the source code for <code>UIAlertView.m</code>?</p>