ADClusterMapView is a drop-in subclass of MKMapView that displays and animates clusters of annotations. This is very useful in cases where you have to display many annotations on the map. Concept and implementation were described on Applidium's website.

1. Add the content of the ADClusterMapView folder to your iOS project
2. Link against the MapKit and CoreLocation frameworks if you don't already
3. Turn your MKMapView instance into a subclass of ADClusterMapView
4. Set your annotations by calling setAnnotations:. Do not use addAnnotation: or addAnnotations: as they are not supported yet.

If you are not using ARC in your project, add the -fobjc-arc flag to the files of the library in the Build Phases > Compile Sources section in Xcode.

In the mapView:viewForAnnotation: and mapView:viewForClusterAnnotation: implementations of your map view's delegate, you are given an instance of ADClusterAnnotation. You can call [annotation originalAnnotations] to retrieve your original id<MKAnnotation> instances and customize your MKAnnotationView instance like you would do with Map Kit. This is especially useful in the case of a leaf annotation, whose originalAnnotations array obviously contains one and only one object.

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation {
    MyAnnotationView * pinView = (MyAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:@"ADClusterableAnnotation"];
    if (!pinView) {
        pinView = [[[MyAnnotationView alloc] initWithAnnotation:annotation
                                                reuseIdentifier:@"ADClusterableAnnotation"]
                   autorelease];
    }
    MyModel * model = [annotation originalAnnotations][0];
    pinView.image = model.image;
    return pinView;
}

We provide you with a few optional methods that you may want to add to your ADClusterMapViewDelegate implementation:

- (NSInteger)numberOfClustersInMapView:(ADClusterMapView *)mapView; // default: 32

- (MKAnnotationView *)mapView:(ADClusterMapView *)mapView viewForClusterAnnotation:(id <MKAnnotation>)annotation; // default: same as returned by mapView:viewForAnnotation:

- (NSString *)clusterTitleForMapView:(ADClusterMapView *)mapView; // default : @"%d elements"

- (BOOL)shouldShowSubtitleForClusterAnnotationsInMapView:(ADClusterMapView *)mapView; // default: YES

- (double)clusterDiscriminationPowerForMapView:(ADClusterMapView *)mapView; // This parameter emphasize the discrimination of annotations which are far away from the center of mass. default: 1.0 (no discrimination applied)

- (void)clusterAnimationDidStopForMapView:(ADClusterMapView *)mapView;

There are a couple of improvements that could be done. Feel free to send us pull requests if you want to contribute!

• Add support for annotations addition and removal.
• Add support for multiple independant trees
• More?