title: In iOS 7, why view height different from the same view in iOS 6
body: <p>I have an view controller which is the root view controller of a <code>UINavigationController</code>, and the <code>UINavigationController</code> is the controller of a <code>UITabBarViewController</code> </p>
  
  <p>like this structure:</p>
  
  <pre><code>UITabBarViewController-&gt;UINavigationViewController-&gt;UIViewController
  </code></pre>
  
  <p>But the problem is, when I use self.view.frame.size.height property of this view controller, I get different result.</p>
  
  <p>In iOS 6, I get 548. But in iOS 7, I get 568. So I can place my custom subview accurately because its position based the height of the view.</p>