Does the Google Maps Android API Utility Cluster Manager have a minimum number of markers before it will create a cluster?

Question

I am using the Google Maps Android API Utility Library to enable clustering in my app. When five or more markers are co-located a cluster is created:

Four or fewer similarly co-located markers won't create a cluster:

Is this by design or am I doing something wrong, because my maps have 2, 3 or 4 markers that clearly overlap, but won't form a cluster?

The code to demonstrate the problem:

Map layout:

<?xml version="1.0" encoding="utf-8"?> <fragment xmlns:android="http://schemas.android.com/apk/res/android"       xmlns:map="http://schemas.android.com/apk/res-auto"       android:id="@+id/map"       android:layout_width="match_parent"       android:layout_height="match_parent"       android:name="com.google.android.gms.maps.SupportMapFragment"/> 

Activity:

    package com.example.android.clusteringminima;      import android.os.Bundle;     import android.support.v4.app.FragmentActivity;      import com.google.android.gms.maps.CameraUpdateFactory;     import com.google.android.gms.maps.GoogleMap;     import com.google.android.gms.maps.SupportMapFragment;     import com.google.android.gms.maps.model.LatLng;     import com.google.maps.android.clustering.ClusterItem;     import com.google.maps.android.clustering.ClusterManager;      public class ClusteringMinimaTest extends FragmentActivity {      private GoogleMap mMap;     private ClusterManager<Place> mClusterManager;      public class Place implements ClusterItem {         private final LatLng mPosition;          public Place(double lat, double lng) {             mPosition = new LatLng(lat, lng);         }          @Override         public LatLng getPosition() {             return mPosition;         }     }      @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.map);         setUpMapIfNeeded();     }      @Override     protected void onResume() {         super.onResume();         setUpMapIfNeeded();     }      private void setUpMapIfNeeded() {         if (mMap != null) {             return;         }         mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();         if (mMap != null) {             mClusterManager = new ClusterManager<Place>(this, mMap);             mMap.setOnCameraChangeListener(mClusterManager);              // Cluster of 4 or 5             mClusterManager.addItem(new Place(51.471524, -0.454280));             mClusterManager.addItem(new Place(51.471311, -0.452257));             mClusterManager.addItem(new Place(51.471510, -0.453514));             mClusterManager.addItem(new Place(51.471710, -0.453714));             // Remove this item to create a group of four             mClusterManager.addItem(new Place(51.471810, -0.453714));              // Cluster of 9 (depending on zoom level)             mClusterManager.addItem(new Place(51.517399, -0.177480));             mClusterManager.addItem(new Place(51.509899, -0.134180));             mClusterManager.addItem(new Place(51.495708, -0.144370));             mClusterManager.addItem(new Place(51.496112, -0.144162));             mClusterManager.addItem(new Place(51.512458, -0.118644));             mClusterManager.addItem(new Place(51.518600, -0.081300));             mClusterManager.addItem(new Place(51.530449, -0.125480));             mClusterManager.addItem(new Place(51.513008, -0.088430));             mClusterManager.addItem(new Place(51.505001, -0.086000));              mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(51.5, -0.35), 9));                 }     } } 

Answer 1

UPDATE (3 years after original answer was posted :D)

As pointed out by @schaenk, DefaultClusterRenderer now has setMinClusterSize(int) method which does the same thing.

ORIGINAL ANSWER

The class responsible for making a decision about clustering/not clustering an item is DefaultClusterRenderer. If you look at DefaultClusterRenderer#shouldRenderAsCluster() method - you will see that it starts clustering only when size of cluster is > MIN_CLUSTER_SIZE. In our case MIN_CLUSTER_SIZE = 4.

Unfortunately you cannot change this constant dynamically, so 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         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));         ........     } }