didAddAnnotationViews not getting called always

I added a MKAnnotation delegate handler class into a MKMapView like this.

MapAnnotation *anAnnotation = [[[MapAnnotation alloc] initWithCoordinate:coord] autorelease];
[myMapView addAnnotation:anAnnotation];

The MapAnnotation implements the MKAnnotation.

However didAddAnnotationViews doesnt get called always. Sometimes (rarely) it does and sometimes its not. I checked few places and I have used this correctly. Does it depends on span attributes as well?

MKCoordinateRegion region; MKCoordinateSpan span; span.latitudeDelta=0.005f; span.longitudeDelta=0.005f;

CLLocationCoordinate2D location;

locati开发者_JAVA技巧on.latitude = searchLocation.coordinate.latitude;
location.longitude = searchLocation.coordinate.longitude;

region.span=span;
region.center=location;

[myMapView setRegion:region animated:TRUE];
[myMapView regionThatFits:region];

Whats wrong with this code?

This delegate method is called for annotations that are currently visible i.e. those that are within the map region that is currently displayed on the screen.