fix: android skip posting hash response after detached from engine

mobile/android/app/src/main/kotlin/app/alextran/immich/MainActivity.kt

@@ -9,6 +9,7 @@ import app.alextran.immich.background.BackgroundWorkerFgHostApi
 import app.alextran.immich.background.BackgroundWorkerLockApi
 import app.alextran.immich.connectivity.ConnectivityApi
 import app.alextran.immich.connectivity.ConnectivityApiImpl
+import app.alextran.immich.core.ImmichPlugin
 import app.alextran.immich.images.ThumbnailApi
 import app.alextran.immich.images.ThumbnailsImpl
 import app.alextran.immich.sync.NativeSyncApi
@@ -42,6 +43,14 @@ class MainActivity : FlutterFragmentActivity() {
       flutterEngine.plugins.add(BackgroundServicePlugin())
       flutterEngine.plugins.add(HttpSSLOptionsPlugin())
       flutterEngine.plugins.add(backgroundEngineLockImpl)
+      flutterEngine.plugins.add(nativeSyncApiImpl)
+    }
+
+    fun cancelPlugins(flutterEngine: FlutterEngine) {
+      val nativeApi =
+        flutterEngine.plugins.get(NativeSyncApiImpl26::class.java) as ImmichPlugin?
+          ?: flutterEngine.plugins.get(NativeSyncApiImpl30::class.java) as ImmichPlugin?
+      nativeApi?.detachFromEngine()
     }
   }
 }

mobile/android/app/src/main/kotlin/app/alextran/immich/background/BackgroundEngineLock.kt

@@ -2,12 +2,13 @@ package app.alextran.immich.background
 
 import android.content.Context
 import android.util.Log
+import app.alextran.immich.core.ImmichPlugin
 import io.flutter.embedding.engine.plugins.FlutterPlugin
 import java.util.concurrent.atomic.AtomicInteger
 
 private const val TAG = "BackgroundEngineLock"
 
-class BackgroundEngineLock(context: Context) : BackgroundWorkerLockApi, FlutterPlugin {
+class BackgroundEngineLock(context: Context) : BackgroundWorkerLockApi, ImmichPlugin() {
   private val ctx: Context = context.applicationContext
 
   companion object {
@@ -41,12 +42,14 @@ class BackgroundEngineLock(context: Context) : BackgroundWorkerLockApi, FlutterP
   }
 
   override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+    super.onAttachedToEngine(binding)
     checkAndEnforceBackgroundLock(binding.applicationContext)
     engineCount.incrementAndGet()
     Log.i(TAG, "Flutter engine attached. Attached Engines count: $engineCount")
   }
 
   override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+    super.onDetachedFromEngine(binding)
     engineCount.decrementAndGet()
     Log.i(TAG, "Flutter engine detached. Attached Engines count: $engineCount")
   }

mobile/android/app/src/main/kotlin/app/alextran/immich/background/BackgroundWorker.kt

@@ -190,6 +190,9 @@ class BackgroundWorker(context: Context, params: WorkerParameters) :
   private fun complete(success: Result) {
     Log.d(TAG, "About to complete BackupWorker with result: $success")
     isComplete = true
+    if (engine != null) {
+      MainActivity.cancelPlugins(engine!!)
+    }
     engine?.destroy()
     engine = null
     flutterApi = null

mobile/android/app/src/main/kotlin/app/alextran/immich/core/ImmichPlugin.kt

@@ -0,0 +1,29 @@
+package app.alextran.immich.core
+
+import androidx.annotation.CallSuper
+import io.flutter.embedding.engine.plugins.FlutterPlugin
+
+abstract class ImmichPlugin : FlutterPlugin {
+  private var detached: Boolean = false;
+
+  @CallSuper
+  override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+    detached = false;
+  }
+
+  fun detachFromEngine() {
+    detached = true
+  }
+
+  @CallSuper
+  override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+    detachFromEngine()
+  }
+
+  fun <T> completeWhenActive(callback: (T) -> Unit, value: T) {
+    if (detached) {
+      return;
+    }
+    callback(value);
+  }
+}

mobile/android/app/src/main/kotlin/app/alextran/immich/sync/MessagesImplBase.kt

@@ -7,6 +7,7 @@ import android.database.Cursor
 import android.provider.MediaStore
 import android.util.Base64
 import androidx.core.database.getStringOrNull
+import app.alextran.immich.core.ImmichPlugin
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
@@ -27,7 +28,7 @@ sealed class AssetResult {
 }
 
 @SuppressLint("InlinedApi")
-open class NativeSyncApiImplBase(context: Context) {
+open class NativeSyncApiImplBase(context: Context) : ImmichPlugin() {
   private val ctx: Context = context.applicationContext
 
   private var hashTask: Job? = null
@@ -237,7 +238,7 @@ open class NativeSyncApiImplBase(context: Context) {
     callback: (Result<List<HashResult>>) -> Unit
   ) {
     if (assetIds.isEmpty()) {
-      callback(Result.success(emptyList()))
+      completeWhenActive(callback, Result.success(emptyList()))
       return
     }
 
@@ -253,10 +254,10 @@ open class NativeSyncApiImplBase(context: Context) {
           }
         }.awaitAll()
 
-        callback(Result.success(results))
+        completeWhenActive(callback, Result.success(results))
       } catch (e: CancellationException) {
-        callback(
-          Result.failure(
+        completeWhenActive(
+          callback, Result.failure(
             FlutterError(
               HASHING_CANCELLED_CODE,
               "Hashing operation was cancelled",
@@ -265,7 +266,7 @@ open class NativeSyncApiImplBase(context: Context) {
           )
         )
       } catch (e: Exception) {
-        callback(Result.failure(e))
+        completeWhenActive(callback, Result.failure(e))
       }
     }
   }