title: How to enable audio scrubber in iOS Lock Screen control panel?
body: <p>I have the following dictionary for MPNowPlayingInfoCenter</p>
  
  <pre><code>@{MPMediaItemPropertyAlbumTitle: @"First Title",
                                  MPMediaItemPropertyArtwork: [[MPMediaItemArtwork alloc] initWithImage:[UIImage imageNamed:@"Album-Cover.jpg"]],
                                  MPMediaItemPropertyPlaybackDuration:[NSNumber numberWithDouble:self.storyAudioPlayer.duration],
                                  MPNowPlayingInfoPropertyElapsedPlaybackTime:[NSNumber numberWithDouble:self.storyAudioPlayer.currentTime],
                                  MPNowPlayingInfoPropertyPlaybackRate:@1.0
                                  }
  </code></pre>
  
  <p>Everything else is working fine but I can't seek songs using the slider. As shown in the image. What parameter am I missing?</p>
  
  <p><img src="https://i.stack.imgur.com/XklpC.png" alt="Lock screen screenshot"></p>