title: IOS: ActivityIndicator over UITableView... How to?
body: <p>i want display an activity indicator over a uitableview while it's loading data (in another thread). So in the ViewDidLoad method of the UITableViewController:</p>
  
  <pre><code>-(void)viewDidLoad
   {
      [super viewDidLoad];
  
      //I create the activity indicator
      UIActivityIndicatorView *ac = [[UIActivityIndicatorView alloc]  
                        initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
      [ac startAnimating];
  
      //Create the queue to download data from internet
      dispatch_queue_t downloadQueue = dispatch_queue_create("PhotoDownload",NULL); 
      dispatch_async(downloadQueue, ^{
        //Download photo
        .......
        .......
        dispatch_async(dispatch_get_main_queue(), ^{
           ......
           ......
           [ac stopAnimating];
        });
      });
     .......
  </code></pre>
  
  <p>Why the activity indicator don't display over the table view? How can i achieve it?</p>