MKAnnotationView custom button image - ios

Question

I am trying to use a custom image on my MKAnnotationView when I use the following code I get no image on my annotation. I have checked in debug to ensure the image is being properly loaded into the UIImage.
- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation {
MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:#"String"];
if(!annotationView) {
annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:#"String"];
UIButton *directionButton = [UIButton buttonWithType:UIButtonTypeCustom];
UIImage *directionIcon = [UIImage imageNamed:#"IconDirections"];
[directionButton setImage:directionIcon forState:UIControlStateNormal];
annotationView.rightCalloutAccessoryView = directionButton;
}
annotationView.enabled = YES;
annotationView.canShowCallout = YES;
return annotationView;
}

Answer 1

There are two main issues:
The frame of the custom callout button is not set making it essentially invisible.
An MKAnnotationView is being created but its image property (the image of the annotation itself -- not the callout button's) is not set. This makes the whole annotation invisible.
For issue 1, set the button's frame to some appropriate value. For example:
UIImage *directionIcon = [UIImage imageNamed:#"IconDirections"];
directionButton.frame =
CGRectMake(0, 0, directionIcon.size.width, directionIcon.size.height);
For issue 2, set the annotation view's image (or create an MKPinAnnotationView instead):
annotationView.image = [UIImage imageNamed:#"SomeIcon"];
Additionally, you should handle view re-use correctly by updating the annotation property.
Complete example:
- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
{
MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:#"String"];
if(!annotationView) {
annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:#"String"];
annotationView.image = [UIImage imageNamed:#"SomeIcon"];
UIButton *directionButton = [UIButton buttonWithType:UIButtonTypeCustom];
UIImage *directionIcon = [UIImage imageNamed:#"IconDirections"];
directionButton.frame =
CGRectMake(0, 0, directionIcon.size.width, directionIcon.size.height);
[directionButton setImage:directionIcon forState:UIControlStateNormal];
annotationView.rightCalloutAccessoryView = directionButton;
annotationView.enabled = YES;
annotationView.canShowCallout = YES;
}
else {
//update annotation to current if re-using a view
annotationView.annotation = annotation;
}
return annotationView;
}

Answer 2

In order for the callout to be shown, the annotation must be selected. To do this programmatically, call:
[mapView selectAnnotation:annotation animated:YES];
where annotation is the specific MKAnnotation for which you want a callout displayed.
You'll almost certainly want to put this in - (void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)views.
There are a few caveats to consider, so here are two other posts that have some great answers and relevant discussions:
How to trigger MKAnnotationView's callout view without touching the pin?
Wanted: How to reliably, consistently select an MKMapView annotation