ios - Wanted: How to reliably, consistently select an MKMapView annotation

Question

After calling MKMapView's setCenterCoordinate:animated: method (without animation), I'd like to call selectAnnotation:animated: (with animation) so that the annotation pops out from the newly-centered pushpin.

For now, I simply watch for mapViewDidFinishLoadingMap: and then select the annotation. However, this is problematic. For instance, this method isn't called when there's no need to load additional map data. In those cases, my annotation isn't selected. :(

Very well. I could call this immediately after setting the center coordinate instead. Ahh, but in that case it's possible that there is map data to load (but it hasn't finished loading yet). I'd risk calling it too soon, with the animation becoming spotty at best.

Thus, if I understand correctly, it's not a matter of knowing if my coordinate is visible, since it's possible to stray almost a screenful of distance and have to load new map data. Rather, it's a matter of knowing if new map data needs to be loaded, and then acting accordingly.

Any ideas on how to accomplish this, or how to otherwise (reliably) select an annotation after re-centering the map view on the coordinate where that annotation lives?

Clues appreciated - thanks!

Answer 1

I ran into the same problem, but found what seems like a reliable and reasonable solution:

1. Implement the delegate method mapView:didAddAnnotationViews:. When I tried selecting the annotation directly within the delegate method, the callout dropped with the pin! That looked odd, so I add a slight delay of a half-second.

   -(void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)views {
       [self performSelector:@selector(selectInitialAnnotation)
             withObject:nil afterDelay:0.5];
   }
   

2. Select the initial annotation as you'd expect, but calling selectAnnotation:animated;

   -(void)selectInitialAnnotation {
       [self.mapView selectAnnotation:self.initialAnnotation animated:YES];
   }
   

It seems that selectAnnotation:animated: is not called under some conditions. Compare with MKMapView docs:

If the specified annotation is not onscreen, and therefore does not have an associated annotation view, this method has no effect.