feat: Transit Layer Demo & Quality Improvements (#1653)

* feat: update to maps 20.0.0 and add usage attribution

* feat: add transit layer demo

* feat(demo): modernize MainActivity with Compose and fix UI issues

- Replace legacy MainActivity.java/xml with Compose-based MainActivity.kt
- Enforce edge-to-edge support with `enableEdgeToEdge()` and Scaffold
- Organize libs.versions.toml into categorized sections
- Add TransitLayerDemoActivity to demonstrate transit layer usage
- Fix spinner text contrast in ClusterAlgorithmsDemoActivity
- Add material-icons-core dependency to resolve compilation error

* feat(demo): modernize MainActivity with Compose and fix UI issues

- Replace legacy MainActivity.java/xml with Compose-based MainActivity.kt
- Enforce edge-to-edge support with `enableEdgeToEdge()` and Scaffold
- Organize libs.versions.toml into categorized sections
- Add TransitLayerDemoActivity to demonstrate transit layer usage
- Fix spinner text contrast in ClusterAlgorithmsDemoActivity
- Add material-icons-core dependency to resolve compilation error

* Refactor: Extract strings, clean resources, modernize Demo UI

- Updated MainActivity to Compose with Accordion UI
- Extracted hardcoded strings to strings.xml
- Removed unused resources (colors, dimens, raw files)
- Fixed lint warnings for hardcoded text and unused resources
- Updated Demo models to use resource IDs

* Fix: Add missing copyright headers (2026 Google LLC)

* Fix: Update XML copyright headers to match repo style

* Delete demo_transit_layer_material.png

Author: dkhawk

build.gradle.kts

@@ -35,6 +35,13 @@ tasks.register<Delete>("clean") {
     delete(layout.buildDirectory)
 }
 
+tasks.register<Exec>("installAndLaunch") {
+    description = "Installs and launches the demo app."
+    group = "install"
+    dependsOn(":demo:installDebug")
+    commandLine("adb", "shell", "am", "start", "-n", "com.google.maps.android.utils.demo/.MainActivity")
+}
+
 allprojects {
     group = "com.google.maps.android"
     // {x-release-please-start-version}

demo/build.gradle.kts

@@ -20,6 +20,7 @@ plugins {
     id("com.android.application")
     id("com.google.android.libraries.mapsplatform.secrets-gradle-plugin")
     id("kotlin-android")
+    alias(libs.plugins.compose.compiler)
 }
 
 android {
@@ -48,6 +49,7 @@ android {
 
     buildFeatures {
         viewBinding = true
+        compose = true
     }
 
     kotlin {
@@ -76,6 +78,15 @@ dependencies {
 
     testImplementation(libs.junit)
     testImplementation(libs.truth)
+
+    implementation(platform(libs.compose.bom))
+    implementation(libs.activity.compose)
+    implementation(libs.ui)
+    implementation(libs.ui.graphics)
+    implementation(libs.ui.tooling.preview)
+    implementation(libs.material3)
+    implementation(libs.material.icons.core)
+    debugImplementation(libs.ui.tooling)
     // [END_EXCLUDE]
 }
 // [END maps_android_utils_install_snippet]

demo/src/main/AndroidManifest.xml

@@ -134,6 +134,9 @@
         <activity
             android:name=".ClusterAlgorithmsDemoActivity"
             android:exported="true" />
+        <activity
+            android:name=".TransitLayerDemoActivity"
+            android:exported="true" />
 
     </application>
 

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

@@ -43,7 +43,7 @@ protected void startDemo(boolean isRestore) {
         try {
             readItems();
         } catch (JSONException e) {
-            Toast.makeText(this, "Problem reading list of markers.", Toast.LENGTH_LONG).show();
+            Toast.makeText(this, getString(R.string.error_reading_markers), Toast.LENGTH_LONG).show();
         }
     }
 

demo/src/main/java/com/google/maps/android/utils/demo/ClusterAlgorithmsDemoActivity.kt

@@ -64,9 +64,9 @@ class ClusterAlgorithmsDemoActivity : BaseDemoActivity() {
     private fun setupSpinner() {
         val spinner: Spinner = findViewById(R.id.algorithm_spinner)
         val adapter = ArrayAdapter.createFromResource(
-            this, R.array.clustering_algorithms, android.R.layout.simple_spinner_item
+            this, R.array.clustering_algorithms, R.layout.text_view_spinner_item
         )
-        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
+        adapter.setDropDownViewResource(R.layout.text_view_spinner_dropdown_item)
         spinner.adapter = adapter
         spinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
             override fun onItemSelected(

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

@@ -103,7 +103,8 @@ private LatLng getMidpoint() {
     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();
+        Toast.makeText(this, getString(R.string.cluster_info_fmt, cluster.getSize(), 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.

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

@@ -58,10 +58,10 @@ public class CustomAdvancedMarkerClusteringDemoActivity extends BaseDemoActivity
     public void onMapsSdkInitialized(@NonNull MapsInitializer.Renderer renderer) {
         switch (renderer) {
             case LATEST:
-                Log.d("MapsDemo", "The latest version of the renderer is used.");
+                Log.d("MapsDemo", getString(R.string.renderer_latest));
                 break;
             case LEGACY:
-                Log.d("MapsDemo", "The legacy version of the renderer is used.");
+                Log.d("MapsDemo", getString(R.string.renderer_legacy));
                 break;
             default:
                 break;
@@ -100,7 +100,7 @@ private PinConfig.Builder getPinConfig(Person person) {
         @SuppressLint("SetTextI18n")
         private View addTextAsMarker(int size) {
             TextView textView = new TextView(getApplicationContext());
-            textView.setText("I am a cluster of size " + size);
+            textView.setText(getString(R.string.cluster_text_fmt, size));
             textView.setBackgroundColor(Color.BLACK);
             textView.setTextColor(Color.YELLOW);
             return textView;
@@ -130,7 +130,8 @@ protected boolean shouldRenderAsCluster(@NonNull Cluster<Person> cluster) {
     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();
+        Toast.makeText(this, getString(R.string.cluster_info_fmt, cluster.getSize(), 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.

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

@@ -57,28 +57,28 @@ protected void startDemo(boolean isRestore) {
         mMarkerB = getMap().addMarker(new MarkerOptions().position(new LatLng(-33.8291, 151.248)).draggable(true));
         mPolyline = getMap().addPolyline(new PolylineOptions().geodesic(true));
 
-        Toast.makeText(this, "Drag the markers!", Toast.LENGTH_LONG).show();
+        Toast.makeText(this, getString(R.string.drag_the_markers), Toast.LENGTH_LONG).show();
         showDistance();
     }
 
     @SuppressLint("SetTextI18n")
     private void showDistance() {
         double distance = SphericalUtil.computeDistanceBetween(mMarkerA.getPosition(), mMarkerB.getPosition());
-        mTextView.setText("The markers are " + formatNumber(distance) + " apart.");
+        mTextView.setText(getString(R.string.distance_format, formatNumber(distance)));
     }
 
     private void updatePolyline() {
         mPolyline.setPoints(Arrays.asList(mMarkerA.getPosition(), mMarkerB.getPosition()));
     }
 
     private String formatNumber(double distance) {
-        String unit = "m";
+        String unit = getString(R.string.unit_m);
         if (distance < 1) {
             distance *= 1000;
-            unit = "mm";
+            unit = getString(R.string.unit_mm);
         } else if (distance > 1000) {
             distance /= 1000;
-            unit = "km";
+            unit = getString(R.string.unit_km);
         }
 
         return String.format("%4.3f%s", distance, unit);