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?

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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.