title: Capture picture on volume up custom camera overlay ios
body: <p>I am doing an app which take pictures and uploads to server. I am using custom camera overlay, I am showing it using</p>
  
  <pre><code>[self presentModalViewController:self.picker animated:NO];
  </code></pre>
  
  <p>I want to capture picture on pressing volume key up also. I tried this code but no benefit</p>
  
  <pre><code>[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(takePicture:)name:@"AVSystemController_SystemVolumeDidChangeNotification" object:nil];
  </code></pre>
  
  <p>Kindly help me.
  Thanks in advance.</p>