Android: Google Maps Clustermanager behaves weirdly. The cluster icon does not go away sometimes on full zoom. Why?

Question

I wrote the following method to display my markers (clustered). However, some of the clusters work fine - i.e. when I zoom in, the blue cluster icon (that says 10+ for ex) goes away and reveals the individual markers. However, some times, when I zoom in fully, the blue cluster marker is still displayed on full zoom ALONG with one of the individual markers. Why is this happening?

private void displayCluster(List<MyItem> items) {

      mClusterManager = new ClusterManager<MyItem>(this, googleMap);
      mClusterManager.setRenderer(new MyRender(getApplicationContext(),googleMap,mClusterManager));

      googleMap.setOnCameraChangeListener(mClusterManager);
      googleMap.setOnMarkerClickListener(mClusterManager);

       for (MyItem item : items) {
           mClusterManager.addItem(item);
       }
   }

Answer 1

DefaultClusterRenderer decides whether the markers should be clustered or not.This class contains DefaultClusterRenderer#shouldRenderAsCluster() method - in which the clustering starts only when size of cluster is > MIN_CLUSTER_SIZE. Default value of MIN_CLUSTER_SIZE is 4.

You need to extend DefaultClusterRenderer class and override shouldRenderAsCluster() method to provide your own logic:

class CustomRenderer<T extends ClusterItem> extends DefaultClusterRenderer<T>
{
    public CustomRenderer(Context context, GoogleMap map, ClusterManager<T> clusterManager) {
        super(context, map, clusterManager);            
    }

    @Override
    protected boolean shouldRenderAsCluster(Cluster<T> cluster) {
        //start clustering if at least 2 items overlap
        //Change your logic here
        return cluster.getSize() > 1;
    }
}

private void setUpMapIfNeeded() {
    if (mMap != null) {
        return;
    }
    mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();
    if (mMap != null) {
        mClusterManager = new ClusterManager<Place>(this, mMap);
        mClusterManager.setRenderer(new CustomRenderer<Place>(this, mMap, mClusterManager));
        ........
    }
}