title: Resize a view using scrollViewDidScroll
body: <p>I have a problem with UIScrollView.</p>
  
  <pre><code>UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 40,320,500)];
  MKMapView *mapView = [[MKMapView alloc] initWithFrame:CGRectMake(0, 40, 320, 120)];
  </code></pre>
  
  <p>and I overide scrollView</p>
  
  <pre><code>-(void)scrollViewDidScroll:(UIScrollView *)scrollView {
     [mapView setFrame:CGRectMake(0, 40, 320, 120 - scrollView.contentOffset.y)];
  }
  </code></pre>
  
  <p>Everything is ok but it's not smooth when scroll and resize mapView. Is there a better solution?</p>
  
  <p>Thank you.</p>