Why is UIApplicationWillChangeStatusBarFrameNotification not sent when the status bar changes height?
<p>I've been trying to listen for changes in the status bar height – such as when the in-call status bar is shown or hidden, or the same with the internet tethering status bar – by listening for the UIApplicationWillChangeStatusBarFrameNotification notification to be sent.</p>

<p>Fairly straightforward code here...</p>

<pre><code>[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(statusBarWillChangeFrame:) 
                                             name:UIApplicationWillChangeStatusBarFrameNotification
                                           object:nil];
</code></pre>

<p>But the notification never seems to be sent in that case, either on the Simulator by using the "Toggle In-Call Status Bar" option or on the device when a call ends with the application open. In addition, the similar UIApplicationDelegate method is not called.</p>

<p>According to the documentation,</p>

<blockquote>
  <p><strong>UIApplicationWillChangeStatusBarFrameNotification</strong></p>
  
  <p>Posted when the application is about
  to change the frame of the status bar.</p>
  
  <p>The userInfo dictionary contains an
  NSValue object that encapsulates a
  CGRect structure expressing the
  location and size of the new status
  bar frame. Use
  UIApplicationStatusBarFrameUserInfoKey
  to access this value.</p>
</blockquote>

<p>Can anyone explain why this notification is not being sent in response to the in-call status bar being shown or hidden? According to the documentation, it should be.</p>
