@Override
 public void onResume() {
   super.onResume();
   /** observer download change * */
   if (downloadObserver == null) downloadObserver = new DownloadChangeObserver();
   getContentResolver()
       .registerContentObserver(DownloadManagerPro.CONTENT_URI, true, downloadObserver);
   updateView();
 }
 @Override
 protected void onDestroy() {
   super.onDestroy();
   unregisterReceiver(completeReceiver);
 }
 @Override
 public void onPause() {
   super.onPause();
   getContentResolver().unregisterContentObserver(downloadObserver);
 }