title: File.listFiles returns null when it shouldn't
body: <p>I am trying to get list of files existing in the Phone Pictures folder (internal storage, no SDCard inserted) using this:</p>
  
  <pre><code> File file = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
   File[] files = file.listFiles();
  </code></pre>
  
  <p>but files value is always being null.
  I also add this to AndroidManifest.xml </p>
  
  <pre><code> &lt;uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /&gt;
  </code></pre>
  
  <p>Any ideas will be much appreciated, thanks in advance.</p>