iPhone SDK, adding annotations to mapview through a 2nd thread, need to refresh mapview

Im writing an iphone app that needs to display annotations depending on groups like "Petrol Stati开发者_开发问答ons","Restaurant" as user selects. I'm using MBProgressHUD and adding annotations is done in background by a 2nd thread everytime user clicks on a choice. The problem is the new annotations aren't displayed on the screen until I move the map around. Is there anyway to kind of "refresh" or "wake" the mapView to display new annotations immediately after I add them from another thread ? Thanks

Edit: You can create a method that adds the annotations to the mapView after you calculated the coordinates in the background you call.

[controller performSelectorOnMainThread:@selector(addingMethod) withObject:annotation waitUntilDone:NO]