title: Playing a song in DIRECTORY_MUSIC
body: <p>I saved a file into the music directory using this:</p>
  
  <pre><code>request.setDestinationInExternalPublicDir(Environment.DIRECTORY_MUSIC, "SpaceJam.mp3");
  </code></pre>
  
  <p>In my main activity, I'd now like to access it and play it.</p>
  
  <p>How do I retrieve the information of the song so that I can use it with:</p>
  
  <pre><code>mp.setDataSource(??);
  </code></pre>
  
  <p>"mp" being the name of my MediaPlayer. Thanks.</p>