marcosero/msmapclustering

A subclass of MKMapView to cluster annotations

MSMapClustering

A subclass of MKMapView to cluster annotations

MSMapClustering lets you to cluster your annotations inside a map view, like Photos.app does with your photos on the map.

The code is freely adaped from an Apple tutorial of WWDC 2010, I've packed it into these classes to make a reusable component for my future works.

Structure

There are three main classes:

• MSMapClustering, a subclass of MKMapView
• MSMapClusteringDelegate, the class delegate that conforms to protocol <MKMapViewDelegate>
• MSAnnotation, a particular class that conforms to protocol <MKAnnotation>

Usage

Include in your project the three classes above and then create your map view and its delegate:

MSMapClustering *mapView = [[MSMapClustering alloc] init];
mapView.delegate = [[MSMapClusteringDelegate alloc] initWithMapView:mapView];

Add/remove annotations using these methods

- (void)addMSAnnotation:(MSAnnotation *)annotation;
- (void)addMSAnnotations:(NSArray *)annotations;

- (void)removeMSAnnotation:(MSAnnotation *)annotation;
- (void)removeAllMSAnnotations;

Implement the delegate's method in the class MSMapClusteringDelegate (obviously!), but pay attention if you want to change methods already inside it.

If you want, you could change marginFactor and bucketSize parameters in MSMapClusteringDelegate.m.

• marginFactor: this value controls the number of off screen annotations are displayed.
  A bigger number means more annotations, less chance of seeing annotations views pop in but decreased performance.
  A smaller number means fewer annotations, more chance of seeing annotations views pop in but better performance.
• bucketSize: adjust this roughly based on the dimensions of your annotations views.
  Bigger numbers more aggressively coalesce annotations (fewer annotations displayed but better performance). Numbers too small result in overlapping annotations views and too many annotations in screen.

Dependencies

MapKit framework is required.

Demo

Play with it and ask me whatever you want.

License

Apache 2.0 http://www.apache.org/licenses/LICENSE-2.0

msmapclustering's Issues

MSMapClustering may require better removeMSAnnotation or removeMSAnnotations methods

Currently, MSMapClustering has addMSAnnotation and addMSAnnotations to force the annotations added to "((MSMapClusteringDelegate *)self.delegate)._allAnnotationsMapView". This is good.

But we don't have good "remove annotation(s)" methods to handle this quickly.

Currently, what I do is writing 2 lines in my main view controller:
(Note: this example is doing "removing all annotations on the map)

[_mapView removeAnnotations:[_mapView annotations]];
[((MSMapClusteringDelegate *)_mapView.delegate)._allAnnotationsMapView removeAnnotations:[((MSMapClusteringDelegate *)_mapView.delegate)._allAnnotationsMapView annotations]];

It is better if we could have 2 methods
removeMSAnnotation
removeMSAnnotations

Retain cycle regarding MSAnnotation.clusterAnnotation

MSAnnotation has a strong reference to its clusterAnnotation which creates a retain cycle (since clusterAnnotation in turn has a strong reference back to its contained annotations). To break this, I declared clusterAnnotation as weak, and now, MSAnnotations are getting released properly.

MSMapClusteringDelegate needs a removeObserver call to balance addObserver

Thanks for the great class.

Suggestion in MSMapClusteringDelegate.m

We need this to balance the "addObserver call. Otherwise, the app would crash when the map view is unloaded.

• (void)dealloc
  {
  [[NSNotificationCenter defaultCenter] removeObserver:self name:@"AnnotationsAdded" object:nil];
  }