title: Accessing getExternalStorageDirectory
body: <p>Using some pretty simple android code I am trying to access a folder according to the following logic:</p>
  
  <pre><code>public void try_to_navigate_local_dir(){
      Environment e = new Environment();
      ArrayList&lt;String&gt; filesList = new ArrayList&lt;String&gt;();
      String sd_card = Environment.getExternalStorageDirectory().toString() + "/subdir_x";
      File file = new File( sd_card ) ;
      File list[] = file.listFiles();
      for( int i=0; i&lt; list.length; i++) {
          filesList.add( list[i].getName() );
      }
  }
  </code></pre>
  
  <p>Where <code>subdir_x</code> is created by another application on my phone.</p>
  
  <p>I can view in those folders using file manager, yet my code returns null when I try to <code>file.listFiles()</code>.</p>
  
  <p>How may I access these files?</p>