Fix #384 - Show clustered markers in exact same location

demo/AndroidManifest.xml

@@ -56,6 +56,7 @@
         <activity android:name=".HeatmapsPlacesDemoActivity"/>
         <activity android:name=".GeoJsonDemoActivity"/>
         <activity android:name=".KmlDemoActivity"/>
+        <activity android:name=".ClusteringSameLocationActivity"/>
 
     </application>
 

demo/res/raw/markers_same_location.json

@@ -0,0 +1,7 @@
+[
+{ "lat" : 51.503186, "lng" : -0.126446, "title" : "Marker 1", "snippet": "Marker 1"},
+{ "lat" : 51.503186, "lng" : -0.126446, "title" : "Marker 2", "snippet" : "Marker 2"},
+{ "lat" : 51.503186, "lng" : -0.126446, "title" : "Marker 3", "snippet": "Marker 3"},
+{ "lat" : 51.503186, "lng" : -0.126446, "title" : "Marker 4", "snippet": "Marker 4" },
+{ "lat" : 51.503186, "lng" : -0.126446, "title" : "Marker 5", "snippet": "Marker 5"}
+]

demo/src/com/google/maps/android/utils/demo/ClusteringSameLocationActivity.java

@@ -0,0 +1,44 @@
+package com.google.maps.android.utils.demo;
+
+import android.util.Log;
+import android.widget.Toast;
+
+import com.google.android.gms.maps.CameraUpdateFactory;
+import com.google.android.gms.maps.model.LatLng;
+import com.google.maps.android.clustering.ClusterManager;
+import com.google.maps.android.utils.demo.model.MyItem;
+
+import org.json.JSONException;
+
+import java.io.InputStream;
+import java.util.List;
+
+public class ClusteringSameLocationActivity extends BaseDemoActivity {
+
+    private ClusterManager<MyItem> mClusterManager;
+
+    @Override
+    protected void startDemo() {
+        getMap().moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(51.503186, -0.126446), 10));
+
+        mClusterManager = new ClusterManager<>(this, getMap());
+
+        getMap().setOnMarkerClickListener(mClusterManager);
+        getMap().setOnCameraMoveListener(mClusterManager);
+
+        try {
+            readItems();
+
+            mClusterManager.cluster();
+        } catch (JSONException e) {
+            Toast.makeText(this, "Problem reading list of markers.", Toast.LENGTH_LONG).show();
+        }
+    }
+
+    private void readItems() throws JSONException {
+        InputStream inputStream = getResources().openRawResource(R.raw.markers_same_location);
+        List<MyItem> items = new MyItemReader().read(inputStream);
+
+        mClusterManager.addItems(items);
+    }
+}

demo/src/com/google/maps/android/utils/demo/MainActivity.java

@@ -38,6 +38,7 @@ protected void onCreate(Bundle savedInstanceState) {
         addDemo("Clustering", ClusteringDemoActivity.class);
         addDemo("Clustering: Custom Look", CustomMarkerClusteringDemoActivity.class);
         addDemo("Clustering: 2K markers", BigClusteringDemoActivity.class);
+        addDemo("Clustering: Markers in same location", ClusteringSameLocationActivity.class);
         addDemo("PolyUtil.decode", PolyDecodeDemoActivity.class);
         addDemo("PolyUtil.simplify", PolySimplifyDemoActivity.class);
         addDemo("IconGenerator", IconGeneratorDemoActivity.class);

demo/src/com/google/maps/android/utils/demo/model/MyItem.java

@@ -47,6 +47,15 @@ public LatLng getPosition() {
     @Override
     public String getSnippet() { return mSnippet; }
 
+    @Override
+    public ClusterItem copy(double lat, double lng) {
+        MyItem item = new MyItem(lat, lng);
+        item.setSnippet(getSnippet());
+        item.setTitle(getTitle());
+
+        return item;
+    }
+
     /**
      * Set the title of the marker
      * @param title string to be set as title

demo/src/com/google/maps/android/utils/demo/model/Person.java

@@ -44,4 +44,9 @@ public String getTitle() {
     public String getSnippet() {
         return null;
     }
+
+    @Override
+    public ClusterItem copy(double lat, double lng) {
+        return new Person(new LatLng(lat, lng), name, profilePhoto);
+    }
 }

library/src/com/google/maps/android/clustering/ClusterItem.java

@@ -37,4 +37,11 @@ public interface ClusterItem {
      * The description of this marker.
      */
     String getSnippet();
+
+    /**
+     * Produces a copy of the same object but setting the given location.
+     *
+     * @return The new object copied.
+     */
+    ClusterItem copy(double lat, double lng);
 }

library/src/com/google/maps/android/clustering/ClusterManager.java

@@ -27,10 +27,14 @@
 import com.google.maps.android.clustering.algo.Algorithm;
 import com.google.maps.android.clustering.algo.NonHierarchicalDistanceBasedAlgorithm;
 import com.google.maps.android.clustering.algo.PreCachingAlgorithmDecorator;
+import com.google.maps.android.clustering.view.ClusterItemsDistributor;
 import com.google.maps.android.clustering.view.ClusterRenderer;
+import com.google.maps.android.clustering.view.DefaultClusterItemsDistributor;
 import com.google.maps.android.clustering.view.DefaultClusterRenderer;
 
 import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
 import java.util.Set;
 import java.util.concurrent.locks.ReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
@@ -43,6 +47,7 @@
  */
 public class ClusterManager<T extends ClusterItem> implements
         GoogleMap.OnCameraIdleListener,
+        GoogleMap.OnCameraMoveListener,
         GoogleMap.OnMarkerClickListener,
         GoogleMap.OnInfoWindowClickListener {
 
@@ -53,6 +58,7 @@ public class ClusterManager<T extends ClusterItem> implements
     private Algorithm<T> mAlgorithm;
     private final ReadWriteLock mAlgorithmLock = new ReentrantReadWriteLock();
     private ClusterRenderer<T> mRenderer;
+    private ClusterItemsDistributor<T> mClusterItemsDistributor;
 
     private GoogleMap mMap;
     private CameraPosition mPreviousCameraPosition;
@@ -76,7 +82,16 @@ public ClusterManager(Context context, GoogleMap map, MarkerManager markerManage
         mRenderer = new DefaultClusterRenderer<T>(context, map, this);
         mAlgorithm = new PreCachingAlgorithmDecorator<T>(new NonHierarchicalDistanceBasedAlgorithm<T>());
         mClusterTask = new ClusterTask();
+        mClusterItemsDistributor = new DefaultClusterItemsDistributor<>(this);
         mRenderer.onAdd();
+
+        setOnClusterClickListener(new ClusterManager.OnClusterClickListener<T>() {
+
+            @Override
+            public boolean onClusterClick(Cluster<T> cluster) {
+                return handleClusterClick(cluster);
+            }
+        });
     }
 
     public MarkerManager.Collection getMarkerCollection() {
@@ -123,6 +138,10 @@ public void setAnimation(boolean animate) {
         mRenderer.setAnimation(animate);
     }
 
+    public void setClusterItemsDistributor(ClusterItemsDistributor<T> clusterItemsDistributor) {
+        this.mClusterItemsDistributor = clusterItemsDistributor;
+    }
+
     public ClusterRenderer<T> getRenderer() {
         return mRenderer;
     }
@@ -159,6 +178,13 @@ public void addItem(T myItem) {
         }
     }
 
+    public void removeItems(List<T> items) {
+
+        for (T item : items) {
+            removeItem(item);
+        }
+    }
+
     public void removeItem(T item) {
         mAlgorithmLock.writeLock().lock();
         try {
@@ -206,6 +232,15 @@ public void onCameraIdle() {
         cluster();
     }
 
+    @Override
+    public void onCameraMove() {
+
+        // collect markers to the original position if they were relocated
+        if (mMap.getCameraPosition().zoom < mMap.getMaxZoomLevel()) {
+            mClusterItemsDistributor.collect();
+        }
+    }
+
     @Override
     public boolean onMarkerClick(Marker marker) {
         return getMarkerManager().onMarkerClick(marker);
@@ -216,6 +251,49 @@ public void onInfoWindowClick(Marker marker) {
         getMarkerManager().onInfoWindowClick(marker);
     }
 
+    public boolean itemsInSameLocation(Cluster<T> cluster) {
+        Collection<T> items = cluster.getItems();
+
+        if (items.size() < 2) {
+            return false;
+        }
+
+        Iterator<T> iterator = items.iterator();
+        T item = iterator.next();
+
+        double longitude = item.getPosition().longitude;
+        double latitude = item.getPosition().latitude;
+
+        while (iterator.hasNext()) {
+            T t = iterator.next();
+
+            if (Double.compare(longitude, t.getPosition().longitude) != 0 && Double.compare(latitude, t.getPosition().latitude) != 0) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    public boolean handleClusterClick(Cluster<T> cluster) {
+        float maxZoomLevel = mMap.getMaxZoomLevel();
+        float currentZoomLevel = mMap.getCameraPosition().zoom;
+
+        // only show markers if users is in the max zoom level
+        if (currentZoomLevel != maxZoomLevel) {
+            return false;
+        }
+
+        if (!itemsInSameLocation(cluster)) {
+            return false;
+        }
+
+        // relocate the markers as defined in the distributor
+        mClusterItemsDistributor.distribute(cluster);
+
+        return true;
+    }
+
     /**
      * Runs the clustering algorithm in a background thread, then re-paints when results come back.
      */

library/src/com/google/maps/android/clustering/view/ClusterItemsDistributor.java

@@ -0,0 +1,20 @@
+package com.google.maps.android.clustering.view;
+
+import com.google.maps.android.clustering.Cluster;
+import com.google.maps.android.clustering.ClusterItem;
+
+/**
+ * It distributes the items in a cluster.
+ */
+public interface ClusterItemsDistributor<T extends ClusterItem> {
+
+    /**
+     * Proceed with the distribution of the items in a cluster.
+     */
+    void distribute(Cluster<T> cluster);
+
+    /**
+     * Proceed to collect the items back to their previous state.
+     */
+    void collect();
+}

library/src/com/google/maps/android/clustering/view/DefaultClusterItemsDistributor.java

@@ -0,0 +1,72 @@
+package com.google.maps.android.clustering.view;
+
+import com.google.maps.android.clustering.Cluster;
+import com.google.maps.android.clustering.ClusterItem;
+import com.google.maps.android.clustering.ClusterManager;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * The default distributor of items included in a cluster. It distributes the items around the original lat/lng in a given radius.
+ *
+ * @param <T> Cluster item type.
+ */
+public class DefaultClusterItemsDistributor<T extends ClusterItem> implements ClusterItemsDistributor<T> {
+
+    private static final double DEFAULT_RADIUS = 0.00003;
+
+    private static final String DEFAULT_DELETE_LIST = "itemsDeleted";
+
+    private static final String DEFAULT_ADDED_LIST = "itemsAdded";
+
+    private double mDistributionRadius;
+
+    private ClusterManager<T> mClusterManager;
+
+    private Map<String, List<T>> mItemsCache;
+
+    public DefaultClusterItemsDistributor(ClusterManager<T> clusterManager) {
+        this(clusterManager, DEFAULT_RADIUS);
+    }
+
+    public DefaultClusterItemsDistributor(ClusterManager<T> clusterManager, double distributionRadius) {
+        mClusterManager = clusterManager;
+        mDistributionRadius = distributionRadius;
+        mItemsCache = new HashMap<>();
+        mItemsCache.put(DEFAULT_ADDED_LIST, new ArrayList<T>());
+        mItemsCache.put(DEFAULT_DELETE_LIST, new ArrayList<T>());
+    }
+
+    @Override
+    public void distribute(Cluster<T> cluster) {
+        // relocate the markers around the original markers position
+        int counter = 0;
+        float rotateFactor = (360 / cluster.getItems().size());
+
+        for (T item : cluster.getItems()) {
+            double lat = item.getPosition().latitude + (mDistributionRadius * Math.cos(++counter * rotateFactor));
+            double lng = item.getPosition().longitude + (mDistributionRadius * Math.sin(counter * rotateFactor));
+            T copy = (T) item.copy(lat, lng);
+
+            mClusterManager.removeItem(item);
+            mClusterManager.addItem(copy);
+            mClusterManager.cluster();
+
+            mItemsCache.get(DEFAULT_ADDED_LIST).add(copy);
+            mItemsCache.get(DEFAULT_DELETE_LIST).add(item);
+        }
+    }
+
+    public void collect() {
+        // collect the items
+        mClusterManager.removeItems(mItemsCache.get(DEFAULT_ADDED_LIST));
+        mClusterManager.addItems(mItemsCache.get(DEFAULT_DELETE_LIST));
+        mClusterManager.cluster();
+
+        mItemsCache.get(DEFAULT_ADDED_LIST).clear();
+        mItemsCache.get(DEFAULT_DELETE_LIST).clear();
+    }
+}

library/tests/src/com/google/maps/android/clustering/QuadItemTest.java

@@ -44,6 +44,11 @@ public String getTitle() {
         public String getSnippet() {
             return null;
         }
+
+        @Override
+        public TestingItem copy(double lat, double lng) {
+            return new TestingItem(lat, lng);
+        }
     }
 
     public void setUp() {