fix(storage): keep tasks alive when snapshotEvents listeners cancel, and scope Android task registries per engine

.github/workflows/android_unit_tests.yaml

@@ -43,7 +43,7 @@ jobs:
         # Tasks are listed per package rather than using the root testDebugUnitTest
         # task, which would also build the Dart sources of the aggregate test app.
         # Add a task here when a package gains an android/src/test directory.
-        run: cd tests/android && ./gradlew :firebase_crashlytics:testDebugUnitTest :cloud_functions:testDebugUnitTest
+        run: cd tests/android && ./gradlew :firebase_crashlytics:testDebugUnitTest :cloud_functions:testDebugUnitTest :firebase_storage:testDebugUnitTest
       - name: 'Upload test reports'
         if: failure()
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a

packages/firebase_storage/firebase_storage/android/build.gradle

@@ -85,6 +85,11 @@ android {
         implementation platform("com.google.firebase:firebase-bom:${getRootProjectExtOrCoreProperty("FirebaseSDKVersion", firebaseCoreProject)}")
         implementation 'com.google.firebase:firebase-storage'
         implementation 'androidx.annotation:annotation:1.7.0'
+        testImplementation 'junit:junit:4.13.2'
+    }
+
+    testOptions {
+        unitTests.returnDefaultValues = true
     }
 }
 

packages/firebase_storage/firebase_storage/android/src/main/kotlin/io/flutter/plugins/firebase/storage/FlutterFirebaseStoragePlugin.kt

@@ -30,12 +30,17 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
   private var channel: MethodChannel? = null
   private var messenger: BinaryMessenger? = null
 
+  // Per instance, as each engine attaches its own plugin instance and numbers its tasks from 0.
+  private val inProgressTasks = FlutterFirebaseStorageTaskRegistry<FlutterFirebaseStorageTask>()
+  private val eventChannels: MutableMap<String, EventChannel> = HashMap()
+  private val streamHandlers: MutableMap<String, StreamHandler> = HashMap()
+
   override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
     initInstance(binding.binaryMessenger)
   }
 
   override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
-    FlutterFirebaseStorageTask.cancelInProgressTasks()
+    cancelInProgressTasks()
     channel?.setMethodCallHandler(null)
     checkNotNull(messenger)
     FirebaseStorageHostApi.setUp(messenger!!, null)
@@ -51,6 +56,11 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
     this.messenger = messenger
   }
 
+  private fun cancelInProgressTasks() {
+    inProgressTasks.removeAll().forEach { it.destroy() }
+  }
+
+  @Synchronized
   private fun registerEventChannel(
       prefix: String,
       identifier: String,
@@ -64,6 +74,12 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
     return identifier
   }
 
+  @Synchronized
+  private fun removeEventChannel(identifier: String) {
+    eventChannels.remove(identifier)?.setStreamHandler(null)
+    streamHandlers.remove(identifier)
+  }
+
   @Synchronized
   private fun removeEventListeners() {
     val eventChannelKeys: List<String> = ArrayList(eventChannels.keys)
@@ -284,10 +300,11 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
     val androidMetaData = getMetaDataFromPigeon(settableMetaData)
     val storageTask =
         FlutterFirebaseStorageTask.uploadBytes(
-            handle.toInt(), androidReference, data, androidMetaData)
+            handle.toInt(), androidReference, data, androidMetaData, inProgressTasks)
     try {
       val identifier = UUID.randomUUID().toString().lowercase(Locale.US)
-      val handler = storageTask.startTaskWithMethodChannel(channel!!, identifier)
+      val handler =
+          storageTask.startTaskWithMethodChannel(channel!!, identifier, ::removeEventChannel)
       callback(
           Result.success(
               registerEventChannel(
@@ -311,10 +328,11 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
     val bytes = stringToByteData(data, format.toInt())
     val storageTask =
         FlutterFirebaseStorageTask.uploadBytes(
-            handle.toInt(), androidReference, bytes!!, androidMetaData)
+            handle.toInt(), androidReference, bytes!!, androidMetaData, inProgressTasks)
     try {
       val identifier = UUID.randomUUID().toString().lowercase(Locale.US)
-      val handler = storageTask.startTaskWithMethodChannel(channel!!, identifier)
+      val handler =
+          storageTask.startTaskWithMethodChannel(channel!!, identifier, ::removeEventChannel)
       callback(
           Result.success(
               registerEventChannel(
@@ -338,10 +356,12 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
             handle.toInt(),
             androidReference,
             Uri.fromFile(File(filePath)),
-            settableMetaData?.let { getMetaDataFromPigeon(it) })
+            settableMetaData?.let { getMetaDataFromPigeon(it) },
+            inProgressTasks)
     try {
       val identifier = UUID.randomUUID().toString().lowercase(Locale.US)
-      val handler = storageTask.startTaskWithMethodChannel(channel!!, identifier)
+      val handler =
+          storageTask.startTaskWithMethodChannel(channel!!, identifier, ::removeEventChannel)
       callback(
           Result.success(
               registerEventChannel(
@@ -360,10 +380,12 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
   ) {
     val androidReference = getReferenceFromPigeon(app, reference)
     val storageTask =
-        FlutterFirebaseStorageTask.downloadFile(handle.toInt(), androidReference, File(filePath))
+        FlutterFirebaseStorageTask.downloadFile(
+            handle.toInt(), androidReference, File(filePath), inProgressTasks)
     try {
       val identifier = UUID.randomUUID().toString().lowercase(Locale.US)
-      val handler = storageTask.startTaskWithMethodChannel(channel!!, identifier)
+      val handler =
+          storageTask.startTaskWithMethodChannel(channel!!, identifier, ::removeEventChannel)
       callback(
           Result.success(
               registerEventChannel(
@@ -378,7 +400,7 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
       handle: Long,
       callback: (Result<Map<String, Any>>) -> Unit
   ) {
-    val storageTask = FlutterFirebaseStorageTask.getInProgressTaskForHandle(handle.toInt())
+    val storageTask = inProgressTasks.get(handle.toInt())
     if (storageTask == null) {
       val statusMap = HashMap<String, Any>()
       statusMap["status"] = false
@@ -407,7 +429,7 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
       handle: Long,
       callback: (Result<Map<String, Any>>) -> Unit
   ) {
-    val storageTask = FlutterFirebaseStorageTask.getInProgressTaskForHandle(handle.toInt())
+    val storageTask = inProgressTasks.get(handle.toInt())
     if (storageTask == null) {
       val statusMap = HashMap<String, Any>()
       statusMap["status"] = false
@@ -436,7 +458,7 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
       handle: Long,
       callback: (Result<Map<String, Any>>) -> Unit
   ) {
-    val storageTask = FlutterFirebaseStorageTask.getInProgressTaskForHandle(handle.toInt())
+    val storageTask = inProgressTasks.get(handle.toInt())
     if (storageTask == null) {
       val statusMap = HashMap<String, Any>()
       statusMap["status"] = false
@@ -501,7 +523,7 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
   override fun didReinitializeFirebaseCore(): Task<Void> {
     val taskCompletionSource = TaskCompletionSource<Void>()
     cachedThreadPool.execute {
-      FlutterFirebaseStorageTask.cancelInProgressTasks()
+      cancelInProgressTasks()
       taskCompletionSource.setResult(null)
       removeEventListeners()
     }
@@ -513,9 +535,6 @@ class FlutterFirebaseStoragePlugin : FlutterFirebasePlugin, FlutterPlugin, Fireb
     const val STORAGE_TASK_EVENT_NAME = "taskEvent"
     const val DEFAULT_ERROR_CODE = "firebase_storage"
 
-    val eventChannels: MutableMap<String, EventChannel> = HashMap()
-    val streamHandlers: MutableMap<String, StreamHandler> = HashMap()
-
     fun getExceptionDetails(exception: Exception): Map<String, String> {
       val storageException = FlutterFirebaseStorageException.parserExceptionToFlutter(exception)
       val details: MutableMap<String, String> = HashMap()

packages/firebase_storage/firebase_storage/android/src/main/kotlin/io/flutter/plugins/firebase/storage/FlutterFirebaseStorageTask.kt

@@ -6,7 +6,6 @@
 package io.flutter.plugins.firebase.storage
 
 import android.net.Uri
-import android.util.SparseArray
 import androidx.annotation.NonNull
 import com.google.firebase.storage.FileDownloadTask
 import com.google.firebase.storage.StorageMetadata
@@ -24,7 +23,8 @@ private constructor(
     private val reference: StorageReference,
     private val bytes: ByteArray?,
     private val fileUri: Uri?,
-    private val metadata: StorageMetadata?
+    private val metadata: StorageMetadata?,
+    private val inProgressTasks: FlutterFirebaseStorageTaskRegistry<FlutterFirebaseStorageTask>
 ) {
   private val pauseSyncObject = Object()
   private val resumeSyncObject = Object()
@@ -33,12 +33,13 @@ private constructor(
   private var destroyed: Boolean = false
 
   init {
-    synchronized(inProgressTasks) { inProgressTasks.put(handle, this) }
+    inProgressTasks.put(handle, this)
   }
 
   fun startTaskWithMethodChannel(
       @NonNull channel: MethodChannel,
-      @NonNull identifier: String
+      @NonNull identifier: String,
+      onCancelled: (String) -> Unit
   ): TaskStateChannelStreamHandler {
     storageTask =
         when (type) {
@@ -51,7 +52,8 @@ private constructor(
           FlutterFirebaseStorageTaskType.DOWNLOAD -> reference.getFile(fileUri!!)
         }
 
-    return TaskStateChannelStreamHandler(this, reference.storage, storageTask as Any, identifier)
+    return TaskStateChannelStreamHandler(
+        this, reference.storage, storageTask as Any, identifier, onCancelled)
   }
 
   fun getSnapshot(): Any = storageTask.snapshot
@@ -88,76 +90,68 @@ private constructor(
     if (destroyed) return
     destroyed = true
 
-    synchronized(inProgressTasks) {
-      if (storageTask.isInProgress || storageTask.isPaused) {
-        storageTask.cancel()
-      }
-      inProgressTasks.remove(handle)
+    if (storageTask.isInProgress || storageTask.isPaused) {
+      storageTask.cancel()
     }
+    inProgressTasks.remove(handle, this)
 
     synchronized(cancelSyncObject) { cancelSyncObject.notifyAll() }
     synchronized(pauseSyncObject) { pauseSyncObject.notifyAll() }
     synchronized(resumeSyncObject) { resumeSyncObject.notifyAll() }
   }
 
   companion object {
-    val inProgressTasks: SparseArray<FlutterFirebaseStorageTask> = SparseArray()
-
-    @JvmStatic
-    fun getInProgressTaskForHandle(handle: Int): FlutterFirebaseStorageTask? {
-      synchronized(inProgressTasks) {
-        return inProgressTasks.get(handle)
-      }
-    }
-
-    @JvmStatic
-    fun cancelInProgressTasks() {
-      synchronized(inProgressTasks) {
-        val tasks = ArrayList<FlutterFirebaseStorageTask>(inProgressTasks.size())
-        for (i in 0 until inProgressTasks.size()) {
-          val task: FlutterFirebaseStorageTask? = inProgressTasks.valueAt(i)
-          task?.let { tasks.add(it) }
-        }
-        inProgressTasks.clear()
-        tasks.forEach { it.destroy() }
-      }
-    }
-
     @JvmStatic
     fun uploadBytes(
         handle: Int,
         reference: StorageReference,
         data: ByteArray,
-        metadata: StorageMetadata?
+        metadata: StorageMetadata?,
+        inProgressTasks: FlutterFirebaseStorageTaskRegistry<FlutterFirebaseStorageTask>
     ): FlutterFirebaseStorageTask {
       return FlutterFirebaseStorageTask(
-          FlutterFirebaseStorageTaskType.BYTES, handle, reference, data, null, metadata)
+          FlutterFirebaseStorageTaskType.BYTES,
+          handle,
+          reference,
+          data,
+          null,
+          metadata,
+          inProgressTasks)
     }
 
     @JvmStatic
     fun uploadFile(
         handle: Int,
         reference: StorageReference,
         fileUri: Uri,
-        metadata: StorageMetadata?
+        metadata: StorageMetadata?,
+        inProgressTasks: FlutterFirebaseStorageTaskRegistry<FlutterFirebaseStorageTask>
     ): FlutterFirebaseStorageTask {
       return FlutterFirebaseStorageTask(
-          FlutterFirebaseStorageTaskType.FILE, handle, reference, null, fileUri, metadata)
+          FlutterFirebaseStorageTaskType.FILE,
+          handle,
+          reference,
+          null,
+          fileUri,
+          metadata,
+          inProgressTasks)
     }
 
     @JvmStatic
     fun downloadFile(
         handle: Int,
         reference: StorageReference,
-        file: File
+        file: File,
+        inProgressTasks: FlutterFirebaseStorageTaskRegistry<FlutterFirebaseStorageTask>
     ): FlutterFirebaseStorageTask {
       return FlutterFirebaseStorageTask(
           FlutterFirebaseStorageTaskType.DOWNLOAD,
           handle,
           reference,
           null,
           Uri.fromFile(file),
-          null)
+          null,
+          inProgressTasks)
     }
 
     @JvmStatic

packages/firebase_storage/firebase_storage/android/src/main/kotlin/io/flutter/plugins/firebase/storage/FlutterFirebaseStorageTaskRegistry.kt

@@ -0,0 +1,35 @@
+// Copyright 2026, the Chromium project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+package io.flutter.plugins.firebase.storage
+
+/**
+ * The in-progress tasks of one plugin instance, keyed by their Dart handle.
+ *
+ * Handles come from a per-isolate counter, so each Flutter engine needs its own registry: with a
+ * shared one, engines overwrite each other's tasks, and detaching one engine cancels them all.
+ */
+internal class FlutterFirebaseStorageTaskRegistry<T : Any> {
+  private val tasks = HashMap<Int, T>()
+
+  @Synchronized
+  fun put(handle: Int, task: T) {
+    tasks[handle] = task
+  }
+
+  @Synchronized fun get(handle: Int): T? = tasks[handle]
+
+  /** Removes [task], unless [handle] now belongs to another task. */
+  @Synchronized
+  fun remove(handle: Int, task: T) {
+    if (tasks[handle] === task) tasks.remove(handle)
+  }
+
+  /** Removes and returns all tasks. */
+  @Synchronized
+  fun removeAll(): List<T> {
+    val all = ArrayList(tasks.values)
+    tasks.clear()
+    return all
+  }
+}