Question

Im trying to show the UIActivityIndicator on my NavigationBar in this MapView with the following code. However, no matter which way I try I cannot show it. Whats the trick here? Also, I am trying to do the map annotations fetching from server and showing on the map in the background, is this the way to do it?

 - (void)viewDidLoad
 {
  [super viewDidLoad];

  self.activityIndicatorView = [[UIActivityIndicatorView alloc]                            
              initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
  self.activityIndicatorView.hidesWhenStopped = YES;
  self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]
                                    initWithCustomView:self.activityIndicatorView];

 [self.activityIndicatorView startAnimating];
 [self performSelectorInBackground:@selector(loadMapAnnotations) withObject: nil];
 [self.activityIndicatorView stopAnimating];
 }

 //=========================================================================
 -(void)loadMapAnnotations
 {
   self.mapView.showsUserLocation = YES;
   if(self.vManager = [VendorManager getVendorManager])
   {
     NSLog(@"VendorManager = %@",[self.vManager description] );

     [self.vManager vendorsNearLocation:userLocation block:^(NSArray *vendors, 
      NSError *error)
      {
          if(vendors && [vendors count])
          {
             for (id v in vendors)
             {
                 Vendor *aVendor = [[Vendor alloc] initWithAttributes:v];
                 NSLog(@"Vendor from Vendors = %@",[aVendor name]);
                 [self.mapView addAnnotation:aVendor];
              }
         }
         else
         {
             NSLog(@"Failed to get vendors: %@", [error description] );
         }


      }];
     }
    }

Answer 1

You’re hiding the activity indicator immediately after you show it.

[self.activityIndicatorView startAnimating];
[self performSelectorInBackground:@selector(loadMapAnnotations) withObject: nil];
[self.activityIndicatorView stopAnimating];

The problem is that you think that performSelectorInBackground:withObject: waits for the method to complete – I don’t really understand why you think it does, since it implicitly has its asynchronous behavior in its name…

Nevertheless, moving the [self.activityIndicatorView stopAnimating]; call to the callback block will solve this “problem”.