public synchronized void closeApplication(final Activity activity) {
   if (getNavigationService() != null) {
     Builder bld = new AlertDialog.Builder(activity);
     bld.setMessage(R.string.background_service_is_enabled_question);
     bld.setPositiveButton(
         R.string.default_buttons_yes,
         new DialogInterface.OnClickListener() {
           @Override
           public void onClick(DialogInterface dialog, int which) {
             closeApplicationAnyway(activity, true);
           }
         });
     bld.setNegativeButton(
         R.string.default_buttons_no,
         new DialogInterface.OnClickListener() {
           @Override
           public void onClick(DialogInterface dialog, int which) {
             closeApplicationAnyway(activity, false);
           }
         });
     bld.show();
   } else {
     closeApplicationAnyway(activity, true);
   }
 }