[google_maps_flutter] Add ability to perform Google Maps SDK warmup

packages/google_maps_flutter/google_maps_flutter_android/android/src/main/java/io/flutter/plugins/googlemaps/GoogleMapInitializer.java

@@ -5,16 +5,19 @@
 package io.flutter.plugins.googlemaps;
 
 import android.content.Context;
+import android.util.Log;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 import com.google.android.gms.maps.MapsInitializer;
+import com.google.android.gms.maps.MapView;
 import com.google.android.gms.maps.OnMapsSdkInitializedCallback;
 import io.flutter.plugin.common.BinaryMessenger;
 
 /** GoogleMaps initializer used to initialize the Google Maps SDK with preferred settings. */
 final class GoogleMapInitializer
     implements OnMapsSdkInitializedCallback, Messages.MapsInitializerApi {
+  private static final String TAG = "GoogleMapInitializer";
   private final Context context;
   private static Messages.Result<Messages.PlatformRendererType> initializationResult;
   private boolean rendererInitialized = false;
@@ -41,6 +44,29 @@ public void initializeWithPreferredRenderer(
     }
   }
 
+  @Override
+  public void warmup(@NonNull Messages.VoidResult result) {
+      Log.i(TAG, "Google Maps warmup started.");
+      try {
+        // This creates a fake map view in order to trigger the SDK's
+        // initialization. For context, see
+        // https://github.com/flutter/flutter/issues/28493#issuecomment-2919150669.
+        MapView mv = new MapView(context);
+        mv.onCreate(null);
+        mv.onPause();
+        mv.onDestroy();
+        Log.i(TAG, "Maps warmup complete.");
+        result.success();
+      } catch (Exception e) {
+        result.error(
+          new Messages.FlutterError(
+              "Could not warm up",
+              e.toString(),
+              null));
+      }
+  }
+
+
   /**
    * Initializes map renderer to with preferred renderer type.
    *