What I want to do is to show vertical scroll bar (indicator) always, even after I call tableView.reloadData().
I found some good solution without reloadData(), like https://stackoverflow.com/a/15613852/8963597 or https://stackoverflow.com/a/40890158/8963597, but once I do call reloadData() since the number of items and content of tableView should change, indicator shows a wrong position/has the wrong size (Sometimes, it should go away, since there is no need for scrolling)