title: UINavigationBar disappears iOS7
body: <p>I have some wierd bug with UINavigationBar.</p>
  
  <p>Sometimes it just disappears (actually if you move view to the half of screen, and then just release it)</p>
  
  <p><img src="https://dl.dropboxusercontent.com/u/30901699/example.gif" alt="gif 5,3mb"></p>
  
  <p><a href="http://youtu.be/hDRaiUFzmRQ" rel="nofollow" title="Video example">Video example</a></p>
  
  <p>In the first ViewController's <code>viewWillAppear:</code> method i call:</p>
  
  <p><code>[self.navigationController setNavigationBarHidden:NO animated:YES];</code></p>
  
  <p>The second ViewController's <code>viewWillAppear:</code> contains:</p>
  
  <p><code>[self.navigationController setNavigationBarHidden:YES animated:NO];</code></p>
  
  <p>I tried change <code>animated:</code> parameter, but it doesn't help.</p>
  
  <p>Is it iOS7 bug or I just doing something wrong?</p>