refactor: session manager lifecycle architecture improvements

android/src/main/kotlin/com/google/maps/flutter/navigation/GoogleMapsNavigationPlugin.kt

@@ -16,6 +16,7 @@
 
 package com.google.maps.flutter.navigation
 
+import android.app.Application
 import androidx.lifecycle.Lifecycle
 import io.flutter.embedding.engine.plugins.FlutterPlugin
 import io.flutter.embedding.engine.plugins.activity.ActivityAware
@@ -69,9 +70,10 @@ class GoogleMapsNavigationPlugin : FlutterPlugin, ActivityAware {
     AutoMapViewApi.setUp(binding.binaryMessenger, autoViewMessageHandler)
     autoViewEventApi = AutoViewEventApi(binding.binaryMessenger)
 
-    // Setup navigation session manager (instance-level, not singleton)
+    // Setup navigation session manager
+    val app = binding.applicationContext as Application
     val navigationSessionEventApi = NavigationSessionEventApi(binding.binaryMessenger)
-    sessionManager = GoogleMapsNavigationSessionManager(navigationSessionEventApi)
+    sessionManager = GoogleMapsNavigationSessionManager(navigationSessionEventApi, app)
 
     // Setup platform view factory and its method channel handlers
     viewEventApi = ViewEventApi(binding.binaryMessenger)

android/src/main/kotlin/com/google/maps/flutter/navigation/GoogleMapsNavigationSessionManager.kt

@@ -17,8 +17,8 @@
 package com.google.maps.flutter.navigation
 
 import android.app.Activity
+import android.app.Application
 import android.location.Location
-import android.util.DisplayMetrics
 import androidx.lifecycle.DefaultLifecycleObserver
 import androidx.lifecycle.LifecycleOwner
 import androidx.lifecycle.Observer
@@ -28,8 +28,6 @@ import com.google.android.libraries.navigation.CustomRoutesOptions
 import com.google.android.libraries.navigation.DisplayOptions
 import com.google.android.libraries.navigation.NavigationApi
 import com.google.android.libraries.navigation.NavigationApi.NavigatorListener
-import com.google.android.libraries.navigation.NavigationUpdatesOptions
-import com.google.android.libraries.navigation.NavigationUpdatesOptions.GeneratedStepImagesType
 import com.google.android.libraries.navigation.Navigator
 import com.google.android.libraries.navigation.Navigator.TaskRemovedBehavior
 import com.google.android.libraries.navigation.RoadSnappedLocationProvider
@@ -52,8 +50,10 @@ interface NavigationReadyListener {
 
 /** This class handles creation of navigation session and other navigation related tasks. */
 class GoogleMapsNavigationSessionManager
-constructor(private val navigationSessionEventApi: NavigationSessionEventApi) :
-  DefaultLifecycleObserver {
+constructor(
+  private val navigationSessionEventApi: NavigationSessionEventApi,
+  private val application: Application,
+) : DefaultLifecycleObserver {
   companion object {
     var navigationReadyListener: NavigationReadyListener? = null
   }
@@ -71,7 +71,7 @@ constructor(private val navigationSessionEventApi: NavigationSessionEventApi) :
     null
   private var speedingListener: SpeedingListener? = null
   private var weakActivity: WeakReference<Activity>? = null
-  private var turnByTurnEventsEnabled: Boolean = false
+  private var navInfoObserver: Observer<NavInfo>? = null
   private var weakLifecycleOwner: WeakReference<LifecycleOwner>? = null
   private var taskRemovedBehavior: @TaskRemovedBehavior Int = 0
 
@@ -221,7 +221,7 @@ constructor(private val navigationSessionEventApi: NavigationSessionEventApi) :
         }
       }
 
-    NavigationApi.getNavigator(getActivity(), listener)
+    NavigationApi.getNavigator(application, listener)
   }
 
   private fun convertNavigatorErrorToFlutterError(
@@ -264,34 +264,29 @@ constructor(private val navigationSessionEventApi: NavigationSessionEventApi) :
     return if (roadSnappedLocationProvider != null) {
       roadSnappedLocationProvider
     } else {
-      val application = getActivity().application
-      if (application != null) {
-        roadSnappedLocationProvider = NavigationApi.getRoadSnappedLocationProvider(application)
-        roadSnappedLocationProvider
-      } else {
-        throw FlutterError(
-          "roadSnappedLocationProviderUnavailable",
-          "Could not get the road snapped location provider, activity not set.",
-        )
-      }
+      roadSnappedLocationProvider = NavigationApi.getRoadSnappedLocationProvider(application)
+      roadSnappedLocationProvider
     }
   }
 
   /** Stops navigation and cleans up internal state of the navigator when it's no longer needed. */
-  fun cleanup() {
-    val navigator = getNavigator()
-    navigator.stopGuidance()
-    navigator.clearDestinations()
-    navigator.simulator.unsetUserLocation()
+  fun cleanup(resetSession: Boolean = true) {
     unregisterListeners()
 
-    // As unregisterListeners() is removing all listeners, we need to re-register them when
-    // navigator is re-initialized. This is done in createNavigationSession() method.
-    GoogleMapsNavigatorHolder.setNavigator(null)
-    navigationReadyListener?.onNavigationReady(false)
+    if (resetSession) {
+      val navigator = getNavigator()
+      navigator.stopGuidance()
+      navigator.clearDestinations()
+      navigator.simulator.unsetUserLocation()
+
+      // As unregisterListeners() is removing all listeners, we need to re-register them when
+      // navigator is re-initialized. This is done in createNavigationSession() method.
+      GoogleMapsNavigatorHolder.reset()
+      navigationReadyListener?.onNavigationReady(false)
+    }
   }
 
-  private fun unregisterListeners() {
+  internal fun unregisterListeners() {
     val navigator = GoogleMapsNavigatorHolder.getNavigator()
     if (navigator != null) {
       if (remainingTimeOrDistanceChangedListener != null) {
@@ -324,7 +319,7 @@ constructor(private val navigationSessionEventApi: NavigationSessionEventApi) :
     if (roadSnappedLocationListener != null) {
       disableRoadSnappedLocationUpdates()
     }
-    if (turnByTurnEventsEnabled) {
+    if (navInfoObserver != null) {
       disableTurnByTurnNavigationEvents()
     }
   }
@@ -557,7 +552,7 @@ constructor(private val navigationSessionEventApi: NavigationSessionEventApi) :
    * @return true if the terms have been accepted by the user, and false otherwise.
    */
   fun areTermsAccepted(): Boolean {
-    return NavigationApi.areTermsAccepted(getActivity().application)
+    return NavigationApi.areTermsAccepted(application)
   }
 
   /**
@@ -566,7 +561,7 @@ constructor(private val navigationSessionEventApi: NavigationSessionEventApi) :
    */
   fun resetTermsAccepted() {
     try {
-      NavigationApi.resetTermsAccepted(getActivity().application)
+      NavigationApi.resetTermsAccepted(application)
     } catch (error: IllegalStateException) {
       throw FlutterError(
         "termsResetNotAllowed",
@@ -690,63 +685,36 @@ constructor(private val navigationSessionEventApi: NavigationSessionEventApi) :
 
   @Throws(FlutterError::class)
   fun enableTurnByTurnNavigationEvents(numNextStepsToPreview: Int) {
-    val lifeCycleOwner: LifecycleOwner? = weakLifecycleOwner?.get()
-    if (!turnByTurnEventsEnabled && lifeCycleOwner != null) {
-
-      /// DisplayMetrics is required to be set for turn-by-turn updates.
-      /// But not used as image generation is disabled.
-      val displayMetrics = DisplayMetrics()
-      displayMetrics.density = 2.0f
-
-      // Configure options for navigation updates.
-      val options =
-        NavigationUpdatesOptions.builder()
-          .setNumNextStepsToPreview(numNextStepsToPreview)
-          .setGeneratedStepImagesType(GeneratedStepImagesType.NONE)
-          .setDisplayMetrics(displayMetrics)
-          .build()
-
-      // Attempt to register the service for navigation updates.
+    if (navInfoObserver == null) {
+      // Register the service centrally (if not already registered)
       val success =
-        getNavigator()
-          .registerServiceForNavUpdates(
-            getActivity().packageName,
-            GoogleMapsNavigationNavUpdatesService::class.java.name,
-            options,
-          )
+        GoogleMapsNavigatorHolder.registerTurnByTurnService(application, numNextStepsToPreview)
 
-      if (success) {
-        val navInfoObserver: Observer<NavInfo> = Observer { navInfo ->
-          navigationSessionEventApi.onNavInfo(Convert.convertNavInfo(navInfo)) {}
-        }
-        GoogleMapsNavigationNavUpdatesService.navInfoLiveData.observe(
-          lifeCycleOwner,
-          navInfoObserver,
-        )
-        turnByTurnEventsEnabled = true
-      } else {
+      if (!success) {
         throw FlutterError(
           "turnByTurnServiceError",
           "Error while registering turn-by-turn updates service.",
         )
       }
+
+      // Create observer for this session manager
+      navInfoObserver = Observer { navInfo ->
+        navigationSessionEventApi.onNavInfo(Convert.convertNavInfo(navInfo)) {}
+      }
+
+      // Add observer using observeForever (works without lifecycle owner)
+      GoogleMapsNavigatorHolder.addNavInfoObserver(navInfoObserver!!)
     }
   }
 
   @Throws(FlutterError::class)
   fun disableTurnByTurnNavigationEvents() {
-    val lifeCycleOwner: LifecycleOwner? = weakLifecycleOwner?.get()
-    if (turnByTurnEventsEnabled && lifeCycleOwner != null) {
-      GoogleMapsNavigationNavUpdatesService.navInfoLiveData.removeObservers(lifeCycleOwner)
-      val success = getNavigator().unregisterServiceForNavUpdates()
-      if (success) {
-        turnByTurnEventsEnabled = false
-      } else {
-        throw FlutterError(
-          "turnByTurnServiceError",
-          "Error while unregistering turn-by-turn updates service.",
-        )
-      }
+    if (navInfoObserver != null) {
+      GoogleMapsNavigatorHolder.removeNavInfoObserver(navInfoObserver!!)
+      navInfoObserver = null
+
+      // Note: Service will only be unregistered when all observers are removed
+      GoogleMapsNavigatorHolder.unregisterTurnByTurnService()
     }
   }
 

android/src/main/kotlin/com/google/maps/flutter/navigation/GoogleMapsNavigationSessionMessageHandler.kt

@@ -37,8 +37,8 @@ class GoogleMapsNavigationSessionMessageHandler(
       GoogleNavigatorInitializationState.INITIALIZED
   }
 
-  override fun cleanup() {
-    sessionManager.cleanup()
+  override fun cleanup(resetSession: Boolean) {
+    sessionManager.cleanup(resetSession)
   }
 
   override fun showTermsAndConditionsDialog(

android/src/main/kotlin/com/google/maps/flutter/navigation/GoogleMapsNavigatorHolder.kt

@@ -1,6 +1,28 @@
+/*
+ * 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
+ *
+ *     https://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.flutter.navigation
 
+import android.app.Application
+import android.util.DisplayMetrics
+import androidx.lifecycle.Observer
+import com.google.android.libraries.mapsplatform.turnbyturn.model.NavInfo
 import com.google.android.libraries.navigation.NavigationApi
+import com.google.android.libraries.navigation.NavigationUpdatesOptions
+import com.google.android.libraries.navigation.NavigationUpdatesOptions.GeneratedStepImagesType
 import com.google.android.libraries.navigation.Navigator
 
 /**
@@ -18,6 +40,10 @@ object GoogleMapsNavigatorHolder {
   private var initializationState = GoogleNavigatorInitializationState.NOT_INITIALIZED
   private val initializationCallbacks = mutableListOf<NavigationApi.NavigatorListener>()
 
+  // Turn-by-turn navigation service management
+  private var turnByTurnServiceRegistered = false
+  private val navInfoObservers = mutableListOf<Observer<NavInfo>>()
+
   @Synchronized fun getNavigator(): Navigator? = navigator
 
   @Synchronized
@@ -51,8 +77,79 @@ object GoogleMapsNavigatorHolder {
     return callbacks
   }
 
+  @Synchronized
+  fun registerTurnByTurnService(application: Application, numNextStepsToPreview: Int): Boolean {
+    val nav = navigator ?: return false
+
+    if (!turnByTurnServiceRegistered) {
+      // DisplayMetrics is required to be set for turn-by-turn updates.
+      // But not used as image generation is disabled.
+      val displayMetrics = DisplayMetrics()
+      displayMetrics.density = 2.0f
+
+      val options =
+        NavigationUpdatesOptions.builder()
+          .setNumNextStepsToPreview(numNextStepsToPreview)
+          .setGeneratedStepImagesType(GeneratedStepImagesType.NONE)
+          .setDisplayMetrics(displayMetrics)
+          .build()
+
+      val success =
+        nav.registerServiceForNavUpdates(
+          application.packageName,
+          GoogleMapsNavigationNavUpdatesService::class.java.name,
+          options,
+        )
+
+      if (success) {
+        turnByTurnServiceRegistered = true
+      }
+      return success
+    }
+    return true // Already registered
+  }
+
+  @Synchronized
+  fun addNavInfoObserver(observer: Observer<NavInfo>) {
+    if (!navInfoObservers.contains(observer)) {
+      navInfoObservers.add(observer)
+      GoogleMapsNavigationNavUpdatesService.navInfoLiveData.observeForever(observer)
+    }
+  }
+
+  @Synchronized
+  fun removeNavInfoObserver(observer: Observer<NavInfo>) {
+    if (navInfoObservers.remove(observer)) {
+      GoogleMapsNavigationNavUpdatesService.navInfoLiveData.removeObserver(observer)
+    }
+  }
+
+  @Synchronized
+  fun unregisterTurnByTurnService(): Boolean {
+    val nav = navigator ?: return false
+
+    if (turnByTurnServiceRegistered && navInfoObservers.isEmpty()) {
+      val success = nav.unregisterServiceForNavUpdates()
+      if (success) {
+        turnByTurnServiceRegistered = false
+      }
+      return success
+    }
+    return true
+  }
+
   @Synchronized
   fun reset() {
+    // Clean up turn-by-turn service
+    if (turnByTurnServiceRegistered) {
+      for (observer in navInfoObservers.toList()) {
+        GoogleMapsNavigationNavUpdatesService.navInfoLiveData.removeObserver(observer)
+      }
+      navInfoObservers.clear()
+      navigator?.unregisterServiceForNavUpdates()
+      turnByTurnServiceRegistered = false
+    }
+
     navigator = null
     initializationState = GoogleNavigatorInitializationState.NOT_INITIALIZED
     initializationCallbacks.clear()

android/src/main/kotlin/com/google/maps/flutter/navigation/messages.g.kt

@@ -5702,7 +5702,7 @@ interface NavigationSessionApi {
 
   fun isInitialized(): Boolean
 
-  fun cleanup()
+  fun cleanup(resetSession: Boolean)
 
   fun showTermsAndConditionsDialog(
     title: String,
@@ -5862,10 +5862,12 @@ interface NavigationSessionApi {
             codec,
           )
         if (api != null) {
-          channel.setMessageHandler { _, reply ->
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val resetSessionArg = args[0] as Boolean
             val wrapped: List<Any?> =
               try {
-                api.cleanup()
+                api.cleanup(resetSessionArg)
                 listOf(null)
               } catch (exception: Throwable) {
                 MessagesPigeonUtils.wrapError(exception)