title: activity indicator hidden has no effect
body: <p>i want hide and start the activity indicator every time the user tap on top of the mkannotationPinView.</p>
  
  <p>this is my code:</p>
  
  <pre><code>-(void)mapView:(MKMapView *)mapView didSelectAnnotationView:(MKAnnotationView *)view
  {
      if (!self.activityIndicator) {
          NSLog(@"error");
      }
      self.activityIndicator.hidden = NO;
      [self.mapView addSubview:self.activityIndicator];
      [self.activityIndicator startAnimating];
      if ([view.leftCalloutAccessoryView isKindOfClass:[UIImageView class]]) {
          UIImageView *imageView = (UIImageView *)(view.leftCalloutAccessoryView);
          if ([view.annotation respondsToSelector:@selector(thumbnail)]) {
              imageView.image = [view.annotation performSelector:@selector(thumbnail)];
          }
      }
      [self.activityIndicator stopAnimating];
  }
  </code></pre>
  
  <p>i have try also to switch <code>[self.mapView addSubview:self.activityIndicator];</code>with         <code>[self.view addSubview:self.activityIndicator];</code>but the effect is the same, notting appare on the view. whats the problem???
  thanks </p>