title: UICollectionView rendering and activityindicator
body: <p>I loaded a <code>UIView</code> from a <code>UIViewController</code>. This <code>UIView</code> contains a (big) <code>UICollectionView</code>.
  The transition from the first <code>UIView</code> to the second <code>UIView</code> is very slow: It seems that when the rendering of all collection's cells is done the second view can show up.
  In the second <code>UIView</code>, I tried.</p>
  
  <pre><code>- (void)viewDidAppear:(BOOL)animated
  {
      [activityView stopAnimating];
      NSLog(@"did appear %@",[NSDate date]);
  }
  - (void)viewWillAppear:(BOOL)animated
  {
        [super viewWillAppear:animated];
        [activityView startAnimating];
        NSLog(@"will appear %@",[NSDate date]);
  }
  </code></pre>
  
  <p>In the <code>NSLog</code>, there is no time difference between the two events, and in fact the second <code>UIView</code> shows up in about 1 second after the event <code>viewDidAppear</code>.
  At this point, I would start a <code>UIActivityIndicator</code>, as in the code. But the indicator is never shown.
  Any hint?</p>