improve lifecycle management

app/android/app/src/main/kotlin/eu/weblibre/gecko/MainActivity.kt

@@ -20,18 +20,53 @@
 package eu.weblibre.gecko
 
 import android.content.Context
+import android.os.Bundle
+import android.util.Log
 import io.flutter.embedding.android.FlutterFragmentActivity
 import io.flutter.embedding.engine.FlutterEngine
 import io.flutter.embedding.engine.FlutterEngineCache
+import io.flutter.embedding.engine.FlutterJNI
 import io.flutter.embedding.engine.dart.DartExecutor
 import io.flutter.plugin.common.MethodChannel
 
 class MainActivity: FlutterFragmentActivity() {
+    companion object {
+        private const val TAG = "MainActivity"
+    }
+
     private val TRIM_MEMORY_CHANNEL = "eu.weblibre.flutter_mozilla_components/trim_memory"
     private val ACTIVITY_CHANNEL = "eu.weblibre.gecko/activity"
     private val ENGINE_ID = "engine_id"
     private var trimMemoryChannel: MethodChannel? = null
 
+    private fun engineTag(engine: FlutterEngine?): String {
+        return engine?.let { "0x${System.identityHashCode(it).toString(16)}" } ?: "null"
+    }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        Log.d(TAG, "onCreate: savedInstanceState=${savedInstanceState != null}, " +
+            "cachedEngine=${engineTag(FlutterEngineCache.getInstance().get(ENGINE_ID))}")
+
+        super.onCreate(null)
+    }
+
+    /**
+     * Check whether the FlutterEngine's native JNI layer is still attached.
+     * Note: binaryMessenger.send() does NOT throw when JNI is detached — it just
+     * logs a warning. We must use reflection to access FlutterJNI.isAttachedToJni().
+     */
+    private fun isEngineNativeAlive(engine: FlutterEngine): Boolean {
+        return try {
+            val field = FlutterEngine::class.java.getDeclaredField("flutterJNI")
+            field.isAccessible = true
+            val jni = field.get(engine) as FlutterJNI
+            jni.isAttached
+        } catch (e: Exception) {
+            Log.w(TAG, "Could not check JNI attachment state: ${e.message}")
+            false
+        }
+    }
+
     override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
         super.configureFlutterEngine(flutterEngine)
 
@@ -48,6 +83,31 @@ class MainActivity: FlutterFragmentActivity() {
         }
     }
 
+    override fun onPause() {
+        Log.d(TAG, "onPause")
+        super.onPause()
+    }
+
+    override fun onDestroy() {
+        Log.d(TAG, "onDestroy: isFinishing=$isFinishing, " +
+            "cachedEngine=${engineTag(FlutterEngineCache.getInstance().get(ENGINE_ID))}")
+        super.onDestroy()
+
+        if (!isFinishing) {
+            val cache = FlutterEngineCache.getInstance()
+            val engine = cache.get(ENGINE_ID)
+            if (engine != null) {
+                Log.d(TAG, "onDestroy: system-initiated destroy, clearing stale engine")
+                cache.remove(ENGINE_ID)
+                try {
+                    engine.destroy()
+                } catch (e: Exception) {
+                    Log.w(TAG, "Error destroying engine in onDestroy", e)
+                }
+            }
+        }
+    }
+
     override fun onTrimMemory(level: Int) {
         super.onTrimMemory(level)
         trimMemoryChannel?.invokeMethod("onTrimMemory", level)
@@ -56,13 +116,26 @@ class MainActivity: FlutterFragmentActivity() {
     override fun provideFlutterEngine(context: Context): FlutterEngine {
         val cache = FlutterEngineCache.getInstance()
         val cachedEngine = cache.get(ENGINE_ID)
-        if (cachedEngine != null && cachedEngine.dartExecutor.isExecutingDart) {
-            return cachedEngine
-        }
-
         if (cachedEngine != null) {
+            val isHealthy = try {
+                cachedEngine.dartExecutor.isExecutingDart && isEngineNativeAlive(cachedEngine)
+            } catch (e: Exception) {
+                Log.w(TAG, "Cached engine health check failed", e)
+                false
+            }
+
+            if (isHealthy) {
+                Log.d(TAG, "provideFlutterEngine: reusing cached engine ${engineTag(cachedEngine)}")
+                return cachedEngine
+            }
+
+            Log.w(TAG, "provideFlutterEngine: cached engine ${engineTag(cachedEngine)} is stale, creating fresh")
             cache.remove(ENGINE_ID)
-            cachedEngine.destroy()
+            try {
+                cachedEngine.destroy()
+            } catch (e: Exception) {
+                Log.w(TAG, "Error destroying stale engine", e)
+            }
         }
 
         val flutterEngine = FlutterEngine(context.applicationContext)
@@ -72,6 +145,7 @@ class MainActivity: FlutterFragmentActivity() {
         )
         cache.put(ENGINE_ID, flutterEngine)
 
+        Log.d(TAG, "provideFlutterEngine: created new engine ${engineTag(flutterEngine)}")
         return flutterEngine
     }
 

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/GeckoPlatformView.kt

@@ -18,13 +18,15 @@ import io.flutter.plugin.platform.PlatformView
 import io.flutter.plugin.platform.PlatformViewFactory
 
 class GeckoViewFactory(
-    private val activity: Activity,
+    private val activityProvider: () -> Activity?,
     private val containerId: Int,
     private val flutterEvents: GeckoStateEvents
     ) : PlatformViewFactory(
     StandardMessageCodec.INSTANCE) {
     override fun create(context: Context?, id: Int, args: Any?): PlatformView {
-        return NativeFragmentView(this.activity, this.containerId, this.flutterEvents)
+        val activity = activityProvider()
+            ?: throw IllegalStateException("No activity available when creating GeckoView platform view")
+        return NativeFragmentView(activity, this.containerId, this.flutterEvents)
     }
 }
 

packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/api/GeckoBrowserApiImpl.kt

@@ -134,26 +134,27 @@ class GeckoBrowserApiImpl : GeckoBrowserApi {
         _flutterPluginBinding = flutterPluginBinding
         _flutterEvents = GeckoStateEvents(_flutterPluginBinding.binaryMessenger)
 
+        // Register platform view factory once per engine binding.
+        // The factory resolves the current activity lazily via activityProvider,
+        // so it always uses the latest activity after recreation/config changes.
+        _flutterPluginBinding.platformViewRegistry.registerViewFactory(
+            "eu.weblibre/gecko", GeckoViewFactory(
+                activityProvider = { this.activity },
+                FRAGMENT_CONTAINER_ID,
+                _flutterEvents
+            )
+        )
+        isPlatformViewRegistered = true
+
         isGeckoInitialized = false
     }
 
     fun attachActivity(activity: Activity) {
         this.activity = activity
-
-        _flutterPluginBinding.platformViewRegistry.registerViewFactory(
-            "eu.weblibre/gecko", GeckoViewFactory(
-                activity,
-                FRAGMENT_CONTAINER_ID,
-                _flutterEvents
-            )
-        )
-
-        isPlatformViewRegistered = true
     }
 
     fun detachActivity() {
         this.activity = null
-        isPlatformViewRegistered = false
     }
 
     override fun getGeckoVersion(): String {

packages/flutter_tor/android/src/main/kotlin/eu/weblibre/flutter_tor/PluggableTransportManager.kt

@@ -10,8 +10,14 @@ import java.io.File
 /**
  * Manages pluggable transports via IPtProxy
  * Supports: obfs4, snowflake, meek, webtunnel
+ *
+ * IMPORTANT: This is a process-level singleton. The IPtProxy.Controller (Go object bound
+ * via gomobile) uses reference tracking that breaks if multiple Controller instances are
+ * created in the same process. By keeping a single PluggableTransportManager (and thus a
+ * single lazy Controller), we avoid "trackGoRef called with Java refnum" crashes when
+ * TorService is destroyed and recreated.
  */
-class PluggableTransportManager(private val context: Context) {
+class PluggableTransportManager private constructor(private val context: Context) {
 
     companion object {
         private const val TAG = "PTManager"
@@ -23,6 +29,17 @@ class PluggableTransportManager(private val context: Context) {
         private val SNOWFLAKE_FRONTS = listOf("foursquare.com", "github.githubassets.com")
         private val SNOWFLAKE_AMP_FRONTS = listOf("www.google.com")
         private const val SNOWFLAKE_ICE_SERVERS = "stun:stun.l.google.com:19302,stun:stun.antisip.com:3478,stun:stun.bluesip.net:3478,stun:stun.dus.net:3478,stun:stun.epygi.com:3478,stun:stun.sonetel.com:3478,stun:stun.uls.co.za:3478,stun:stun.voipgate.com:3478,stun:stun.voys.nl:3478"
+
+        @Volatile
+        private var instance: PluggableTransportManager? = null
+
+        fun getInstance(context: Context): PluggableTransportManager {
+            return instance ?: synchronized(this) {
+                instance ?: PluggableTransportManager(context.applicationContext).also {
+                    instance = it
+                }
+            }
+        }
     }
 
     private val stateDir = File(context.cacheDir, "iptproxy")

packages/flutter_tor/android/src/main/kotlin/eu/weblibre/flutter_tor/TorManager.kt

@@ -35,7 +35,7 @@ class TorManager(
     private var controlConnection: TorControlConnection? = null
     private var torService: TorService? = null
 
-    val pluggableTransportManager = PluggableTransportManager(context)
+    val pluggableTransportManager = PluggableTransportManager.getInstance(context)
     private val geoIpManager = GeoIpManager(context)
 
     private val scope = CoroutineScope(Dispatchers.IO + SupervisorJob())

packages/flutter_tor/android/src/main/kotlin/eu/weblibre/flutter_tor/TorService.kt

@@ -199,9 +199,20 @@ class TorService : Service() {
         super.onDestroy()
         Log.d(TAG, "Service destroyed")
 
-        scope.launch {
-            torManager?.destroy()
-        }
+        // Stop pluggable transports synchronously to release Go references.
+        // Previously this was scope.launch { torManager?.destroy() } followed by
+        // scope.cancel(), which meant the cleanup coroutine was immediately cancelled
+        // and never ran — causing "trackGoRef called with Java refnum" crashes when
+        // TorService was recreated and tried to create a new IPtProxy.Controller.
+        //
+        // Note: We only stop transports here. The PluggableTransportManager singleton
+        // and its Controller persist across service restarts by design.
+        // Full TorManager.destroy() is not called because it would deadlock
+        // (cleanup() uses runBlocking(Dispatchers.Main) while onDestroy runs on Main).
+        torManager?.pluggableTransportManager?.stopAll()
+
+        torManager = null
+        logHandler = null
         scope.cancel()
     }
 }