title: How to restart UIRefreshControl animation?
body: <p>I have several tableviews in a tab bar controller. On some of these I have set a UIRefreshControl.</p>
  
  <p>After swiping down to start a refresh the 'spinner' animation begins. If I select a different tab and then move back to the original tab, the refresh control is still shown but the animation has stopped.</p>
  
  <p>How do I restart this animation?</p>
  
  <p>I've tried starting the refresh again and got no results.
  I also inspected the view hierarchy, hoping to find a UIActivityIndicatorView but could only find a <code>_UIRefreshControlModernReplicatorView</code> that seems to be the view doing the animation. I don't know of any method I can call of this to get the animation restarted.</p>