Updating image in MKAnnotationView

Question

I am writing an application that displays a thumbnail from a server in the leftCalloutAccessoryView. Before I actually get the image, I display a placemark image. Once the photo is downloaded, a method is called and I want to update that image without removing the original annotation and placing another. I just wan the image to switch from the placeholder to the downloaded thumbnail. Below is the code that does not work, but if someone could let me know if I'm on the right track, that would be great.

MyAnnotationClass *annotation=[[MyAnnotationClass alloc] initWithCoordinate:item.location];
[annotation setItem:item];
if(item.title){
    annotation.name=item.title;
}
else{
    annotation.name=@"no title";
}
[annotation setDescription:[[NSString alloc] initWithFormat:@"Views:%d Likes:%d Comments:%d",item.views,item.likes,item.comments]];
[annotation setImage:[[photo.thumb copyWithDimensions: CGSizeMake(32.0, 32.0)] autorelease]];

MKAnnotationView *av=[__mapView viewForAnnotation:annotation];
UIImageView *imageView=[[UIImageView alloc] initWithImage:annotation.image];
imageView.frame=CGRectMake(0.0, 0.0, 32.0, 32.0);
av.leftCalloutAccessoryView=imageView;
[annotation release];

I have been looking around here for quite sometime, but nothing that I can find will do what I need. Thanks

Answer 1

If the annotation is already on the map and you want to update it, don't create a new one.

Instead, find the annotation you want to update in the map view's annotations array and update its properties. Then call viewForAnnotation: on that existing annotation and update the leftCalloutAccessoryView.

Also, make sure the viewForAnnotation delegate method has logic that sets the leftCalloutAccessoryView to either the placeholder image or the actual image by checking the annotation's properties (and not always the placeholder image).

This other question has some sample code that may help.