@Override
 public void onPullUpToRefresh() {
   final int count = mAdapter.getCount();
   final ParcelableStatus status = count > 0 ? mAdapter.getItem(count - 1) : null;
   if (status != null) {
     getStatuses(new long[] {status.account_id}, new long[] {status.status_id}, null);
   }
 }
 @Override
 final long[] getOldestStatusIds() {
   final int last_idx = mAdapter.getCount() - 1;
   final long last_id = last_idx >= 0 ? mAdapter.getItem(last_idx).status_id : -1;
   return last_id > 0 ? new long[] {last_id} : null;
 }
 @Override
 final long[] getNewestStatusIds() {
   final long last_id = mAdapter.getCount() > 0 ? mAdapter.getItem(0).status_id : -1;
   return last_id > 0 ? new long[] {last_id} : null;
 }