title: How to do Orientation Detection even the device has locked orientation
body: <p>I wonder how to perceive orientation changes even if the device's current orientation is locked (by double clicking home button and pressing the grey orientation lock icon)</p>
  
  <p>However, I've seen video taking apps (<code>UIImagePickerController</code>) that can perceive orientation changes and change its control orientation.</p>
  
  <p>I know that for detecting the change, I can use:</p>
  
  <pre><code>- shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
  - UIDeviceOrientationDidChangeNotification
  </code></pre>
  
  <p>but neither of those methods work if the orientation of the device is locked. </p>