title: Read content Uri from File from SharedPreferences and get persistent permission on it
body: <p>my app can be called from file explorer via app chooser.
  I catch the given <code>contentUri</code> from the transmitted PDF file and save the content uri useing <code>sharedPreferences</code>.</p>
  <p>If I start my app again, I want to open the saved PDF file (reading the contentUri from from sharedPreferences) again.
  But no file chooser should be opened anymore.</p>
  <p>But I can't call <code>ACTION_OPEN_DOCUMENT</code> via the App Chooser because I get the <code>uri</code> direct from <code>sharedpreferences</code>. I also can't call
  <code>getContentResolver().takePersistableUriPermission(uri, takeFlags);</code>.</p>
  <p>So I can't get access to this file again.</p>
  <p>How can I get permanent access to the file. Is copying to <code>INTERNAL_STORAGE</code> really the only solution?</p>
  <p>Thanks,
  Alejandro</p>