feat: implementation of diff

.gitignore

@@ -11,4 +11,4 @@ project.properties
 .DS_Store
 .java-version
 secrets.properties
-.kotlin
+.kotlin

demo/build.gradle.kts

@@ -64,6 +64,7 @@ dependencies {
     implementation(libs.kotlin.stdlib.jdk8)
     implementation(libs.kotlinx.coroutines.android)
     implementation(libs.kotlinx.coroutines.core)
+    implementation(libs.material)
 
     testImplementation(libs.junit)
     testImplementation(libs.truth)

demo/src/main/AndroidManifest.xml

@@ -91,6 +91,9 @@
         <activity
             android:name=".CustomAdvancedMarkerClusteringDemoActivity"
             android:exported="true" />
+        <activity
+            android:name=".ClusteringDiffDemoActivity"
+            android:exported="true" />
         <activity
             android:name=".ZoomClusteringDemoActivity"
             android:exported="true" />

demo/src/main/java/com/google/maps/android/utils/demo/ClusteringDiffDemoActivity.java

@@ -0,0 +1,297 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.maps.android.utils.demo;
+
+import android.annotation.SuppressLint;
+import android.graphics.Bitmap;
+import android.graphics.drawable.Drawable;
+import android.util.Log;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ImageView;
+import android.widget.Toast;
+
+import androidx.annotation.NonNull;
+import androidx.core.content.res.ResourcesCompat;
+
+import com.google.android.gms.maps.CameraUpdateFactory;
+import com.google.android.gms.maps.GoogleMap;
+import com.google.android.gms.maps.model.BitmapDescriptor;
+import com.google.android.gms.maps.model.BitmapDescriptorFactory;
+import com.google.android.gms.maps.model.LatLng;
+import com.google.android.gms.maps.model.LatLngBounds;
+import com.google.android.gms.maps.model.Marker;
+import com.google.android.gms.maps.model.MarkerOptions;
+import com.google.maps.android.clustering.Cluster;
+import com.google.maps.android.clustering.ClusterItem;
+import com.google.maps.android.clustering.ClusterManager;
+import com.google.maps.android.clustering.view.ClusterRendererMultipleItems;
+import com.google.maps.android.ui.IconGenerator;
+import com.google.maps.android.utils.demo.model.Person;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Demonstrates how to apply a diff to the current Cluster
+ */
+public class ClusteringDiffDemoActivity extends BaseDemoActivity implements ClusterManager.OnClusterClickListener<Person>, ClusterManager.OnClusterInfoWindowClickListener<Person>, ClusterManager.OnClusterItemClickListener<Person>, ClusterManager.OnClusterItemInfoWindowClickListener<Person> {
+    private ClusterManager<Person> mClusterManager;
+    private Person itemtoUpdate = new Person(ENFIELD, "Teach", R.drawable.teacher);
+
+    private static final LatLng ENFIELD = new LatLng(51.6524, -0.0838);
+    private static final LatLng ILFORD = new LatLng(51.5590, -0.0815);
+
+    private static final LatLng LONDON = new LatLng(51.5074, -0.1278);
+    LatLng midpoint = getMidpoint();
+    private int currentLocationIndex = 0;
+
+    protected int getLayoutId() {
+        return R.layout.map_with_floating_button;
+    }
+
+    @Override
+    public void onMapReady(@NonNull GoogleMap map) {
+        super.onMapReady(map);
+        findViewById(R.id.fab_rotate_location).setOnClickListener(v -> rotateLocation());
+        getMap().animateCamera(CameraUpdateFactory.newLatLngZoom(midpoint, 12));
+    }
+
+
+    private LatLng getMidpoint() {
+        double latitude = (ClusteringDiffDemoActivity.ENFIELD.latitude + ClusteringDiffDemoActivity.ILFORD.latitude + ClusteringDiffDemoActivity.LONDON.latitude) / 3;
+        double longitude = (ClusteringDiffDemoActivity.ENFIELD.longitude + ClusteringDiffDemoActivity.ILFORD.longitude + ClusteringDiffDemoActivity.LONDON.longitude) / 3;
+        return new LatLng(latitude, longitude);
+    }
+
+    /**
+     * Draws profile photos inside markers (using IconGenerator).
+     * When there are multiple people in the cluster, draw multiple photos (using MultiDrawable).
+     */
+    @SuppressLint("InflateParams")
+    private class PersonRenderer extends ClusterRendererMultipleItems<Person> {
+        private final IconGenerator mIconGenerator = new IconGenerator(getApplicationContext());
+        private final IconGenerator mClusterIconGenerator = new IconGenerator(getApplicationContext());
+        private final ImageView mImageView;
+        private final ImageView mClusterImageView;
+        private final int mDimension;
+
+        public PersonRenderer() {
+            super(getApplicationContext(), getMap(), mClusterManager);
+
+            View multiProfile = getLayoutInflater().inflate(R.layout.multi_profile, null);
+            mClusterIconGenerator.setContentView(multiProfile);
+            mClusterImageView = multiProfile.findViewById(R.id.image);
+
+            mImageView = new ImageView(getApplicationContext());
+            mDimension = (int) getResources().getDimension(R.dimen.custom_profile_image);
+            mImageView.setLayoutParams(new ViewGroup.LayoutParams(mDimension, mDimension));
+            int padding = (int) getResources().getDimension(R.dimen.custom_profile_padding);
+            mImageView.setPadding(padding, padding, padding, padding);
+            mIconGenerator.setContentView(mImageView);
+        }
+
+        @Override
+        protected void onBeforeClusterItemRendered(@NonNull Person person, @NonNull MarkerOptions markerOptions) {
+            // Draw a single person - show their profile photo and set the info window to show their name
+            markerOptions
+                    .icon(getItemIcon(person))
+                    .title(person.name);
+        }
+
+        @Override
+        protected void onClusterItemUpdated(@NonNull Person person, @NonNull Marker marker) {
+            // Same implementation as onBeforeClusterItemRendered() (to update cached markers)
+            marker.setIcon(getItemIcon(person));
+            marker.setTitle(person.name);
+        }
+
+        /**
+         * Get a descriptor for a single person (i.e., a marker outside a cluster) from their
+         * profile photo to be used for a marker icon
+         *
+         * @param person person to return an BitmapDescriptor for
+         * @return the person's profile photo as a BitmapDescriptor
+         */
+        private BitmapDescriptor getItemIcon(Person person) {
+            mImageView.setImageResource(person.profilePhoto);
+            Bitmap icon = mIconGenerator.makeIcon();
+            return BitmapDescriptorFactory.fromBitmap(icon);
+        }
+
+        @Override
+        protected void onBeforeClusterRendered(@NonNull Cluster<Person> cluster, @NonNull MarkerOptions markerOptions) {
+            // Draw multiple people.
+            // Note: this method runs on the UI thread. Don't spend too much time in here (like in this example).
+            markerOptions.icon(getClusterIcon(cluster));
+        }
+
+        @Override
+        protected void onClusterUpdated(@NonNull Cluster<Person> cluster, @NonNull Marker marker) {
+            // Same implementation as onBeforeClusterRendered() (to update cached markers)
+            marker.setIcon(getClusterIcon(cluster));
+        }
+
+        /**
+         * Get a descriptor for multiple people (a cluster) to be used for a marker icon. Note: this
+         * method runs on the UI thread. Don't spend too much time in here (like in this example).
+         *
+         * @param cluster cluster to draw a BitmapDescriptor for
+         * @return a BitmapDescriptor representing a cluster
+         */
+        private BitmapDescriptor getClusterIcon(Cluster<Person> cluster) {
+            List<Drawable> profilePhotos = new ArrayList<>(Math.min(4, cluster.getSize()));
+            int width = mDimension;
+            int height = mDimension;
+
+            for (Person p : cluster.getItems()) {
+                // Draw 4 at most.
+                if (profilePhotos.size() == 4) break;
+                Drawable drawable = ResourcesCompat.getDrawable(getBaseContext().getResources(), p.profilePhoto, null);
+                if (drawable != null) {
+                    drawable.setBounds(0, 0, width, height);
+                }
+                profilePhotos.add(drawable);
+            }
+            MultiDrawable multiDrawable = new MultiDrawable(profilePhotos);
+            multiDrawable.setBounds(0, 0, width, height);
+
+            mClusterImageView.setImageDrawable(multiDrawable);
+            Bitmap icon = mClusterIconGenerator.makeIcon(String.valueOf(cluster.getSize()));
+            return BitmapDescriptorFactory.fromBitmap(icon);
+        }
+
+        @Override
+        protected boolean shouldRenderAsCluster(@NonNull Cluster<Person> cluster) {
+            return cluster.getSize() >= 2;
+        }
+    }
+
+
+    @Override
+    public boolean onClusterClick(Cluster<Person> cluster) {
+        // Show a toast with some info when the cluster is clicked.
+        String firstName = cluster.getItems().iterator().next().name;
+        Toast.makeText(this, cluster.getSize() + " (including " + firstName + ")", Toast.LENGTH_SHORT).show();
+
+        // Zoom in the cluster. Need to create LatLngBounds and including all the cluster items
+        // inside of bounds, then animate to center of the bounds.
+
+        // Create the builder to collect all essential cluster items for the bounds.
+        LatLngBounds.Builder builder = LatLngBounds.builder();
+        for (ClusterItem item : cluster.getItems()) {
+            builder.include(item.getPosition());
+        }
+        // Get the LatLngBounds
+        final LatLngBounds bounds = builder.build();
+
+        // Animate camera to the bounds
+        try {
+            getMap().animateCamera(CameraUpdateFactory.newLatLngBounds(bounds, 100));
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+
+        return true;
+    }
+
+    @Override
+    public void onClusterInfoWindowClick(Cluster<Person> cluster) {
+        // Does nothing, but you could go to a list of the users.
+    }
+
+    @Override
+    public boolean onClusterItemClick(Person item) {
+        // Does nothing, but you could go into the user's profile page, for example.
+        return false;
+    }
+
+    @Override
+    public void onClusterItemInfoWindowClick(Person item) {
+        // Does nothing, but you could go into the user's profile page, for example.
+    }
+
+    @Override
+    protected void startDemo(boolean isRestore) {
+        if (!isRestore) {
+            getMap().moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(51.503186, -0.126446), 6));
+        }
+
+        mClusterManager = new ClusterManager<>(this, getMap());
+        mClusterManager.setRenderer(new PersonRenderer());
+        getMap().setOnCameraIdleListener(mClusterManager);
+        getMap().setOnMarkerClickListener(mClusterManager);
+        getMap().setOnInfoWindowClickListener(mClusterManager);
+        mClusterManager.setOnClusterClickListener(this);
+        mClusterManager.setOnClusterInfoWindowClickListener(this);
+        mClusterManager.setOnClusterItemClickListener(this);
+        mClusterManager.setOnClusterItemInfoWindowClickListener(this);
+
+        addItems();
+        mClusterManager.cluster();
+    }
+
+    private void addItems() {
+        // Marker in Enfield
+        mClusterManager.addItem(new Person(ENFIELD, "John", R.drawable.john));
+
+        // Marker in the center of London
+        itemtoUpdate = new Person(LONDON, "Teach", R.drawable.teacher);
+        mClusterManager.addItem(itemtoUpdate);
+    }
+
+    private void rotateLocation() {
+        // Update the current index to cycle through locations (0 = Enfield, 1 = Olford, 2 = London)
+        currentLocationIndex = (currentLocationIndex + 1) % 3;
+
+
+        LatLng newLocation = switch (currentLocationIndex) {
+            case 0 -> ENFIELD;
+            case 1 -> ILFORD;
+            default -> LONDON;
+        };
+
+        String cityName = getCityName(newLocation);
+
+        Log.d("ClusterTest", "Item rotated to: " + newLocation.toString() + ", City: " + cityName);
+
+        if (itemtoUpdate != null) {
+            itemtoUpdate = new Person(newLocation, "Teach", R.drawable.teacher);
+            mClusterManager.updateItem(itemtoUpdate); // Update the marker
+            mClusterManager.cluster();
+        }
+    }
+
+    // Method to map LatLng to city name
+    private String getCityName(LatLng location) {
+        if (areLocationsEqual(location, ENFIELD)) {
+            return "Enfield";
+        } else if (areLocationsEqual(location, ILFORD)) {
+            return "Ilford";
+        } else if (areLocationsEqual(location, LONDON)) {
+            return "London";
+        } else {
+            return "Unknown City"; // Default case if location is not recognized
+        }
+    }
+
+    // Method to compare LatLng objects with a tolerance
+    private boolean areLocationsEqual(LatLng loc1, LatLng loc2) {
+        return Math.abs(loc1.latitude - loc2.latitude) < 1E-5 &&
+                Math.abs(loc1.longitude - loc2.longitude) < 1E-5;
+    }
+}

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

@@ -47,6 +47,7 @@ protected void onCreate(Bundle savedInstanceState) {
         addDemo("Clustering", ClusteringDemoActivity.class);
         addDemo("Advanced Markers Clustering Example", CustomAdvancedMarkerClusteringDemoActivity.class);
         addDemo("Clustering: Custom Look", CustomMarkerClusteringDemoActivity.class);
+        addDemo("Clustering: Diff", ClusteringDiffDemoActivity.class);
         addDemo("Clustering: 2K markers", BigClusteringDemoActivity.class);
         addDemo("Clustering: 20K only visible markers", VisibleClusteringDemoActivity.class);
         addDemo("Clustering: ViewModel", ClusteringViewModelDemoActivity.class);

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

@@ -22,6 +22,9 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
+import java.util.Objects;
+
+
 public class Person implements ClusterItem {
     public final String name;
     public final int profilePhoto;
@@ -54,4 +57,18 @@ public String getSnippet() {
     public Float getZIndex() {
         return null;
     }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(name);
+    }
+
+    // If we use the diff() operation, we need to implement an equals operation, to determine what
+    // makes each ClusterItem unique (which is probably not the position)
+    @Override
+    public boolean equals(@Nullable Object obj) {
+        if (obj != null && getClass() != obj.getClass()) return false;
+        Person myObj = (Person) obj;
+        return this.name.equals(myObj.name);
+    }
 }