Target Android 13 & Make FileOperationService a foreground service

app/build.gradle

@@ -36,7 +36,7 @@ android {
     defaultConfig {
         applicationId "sushi.hardcore.droidfs"
         minSdkVersion 21
-        targetSdkVersion 32
+        targetSdkVersion 33
         versionCode 36
         versionName "2.1.3"
 

app/src/main/AndroidManifest.xml

@@ -4,6 +4,9 @@
     android:installLocation="auto">
 
     <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" tools:ignore="ScopedStorage" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_DATA_SYNC" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
     <uses-permission android:name="android.permission.USE_BIOMETRIC" />
     <uses-permission android:name="android.permission.CAMERA" />
@@ -56,7 +59,7 @@
         <activity android:name=".LogcatActivity"/>
 
         <service android:name=".WiperService" android:exported="false" android:stopWithTask="false"/>
-        <service android:name=".file_operations.FileOperationService" android:exported="false"/>
+        <service android:name=".file_operations.FileOperationService" android:exported="false" android:foregroundServiceType="dataSync"/>
 
         <receiver android:name=".file_operations.NotificationBroadcastReceiver" android:exported="false">
             <intent-filter>

app/src/main/java/sushi/hardcore/droidfs/MainActivity.kt

@@ -132,13 +132,8 @@ class MainActivity : BaseActivity(), VolumeAdapter.Listener {
             }
         }
         startService(Intent(this, WiperService::class.java))
-        Intent(this, FileOperationService::class.java).also {
+        FileOperationService.bind(this) {
-            bindService(it, object : ServiceConnection {
+            fileOperationService = it
-                override fun onServiceConnected(className: ComponentName, service: IBinder) {
-                    fileOperationService = (service as FileOperationService.LocalBinder).getService()
-                }
-                override fun onServiceDisconnected(arg0: ComponentName) {}
-            }, Context.BIND_AUTO_CREATE)
         }
     }
 
@@ -434,9 +429,6 @@ class MainActivity : BaseActivity(), VolumeAdapter.Listener {
         lifecycleScope.launch {
             val result = fileOperationService.copyVolume(srcDocumentFile, dstDocumentFile)
             when (result.taskResult.state) {
-                TaskResult.State.CANCELLED -> {
-                    result.dstRootDirectory?.delete()
-                }
                 TaskResult.State.SUCCESS -> {
                     result.dstRootDirectory?.let {
                         getResultVolume(it)?.let { volume ->
@@ -458,6 +450,7 @@ class MainActivity : BaseActivity(), VolumeAdapter.Listener {
                         .show()
                 }
                 TaskResult.State.ERROR -> result.taskResult.showErrorAlertDialog(this@MainActivity, theme)
+                TaskResult.State.CANCELLED -> {}
             }
         }
     }

app/src/main/java/sushi/hardcore/droidfs/explorers/BaseExplorerActivity.kt

@@ -190,15 +190,9 @@ open class BaseExplorerActivity : BaseActivity(), ExplorerElementAdapter.Listene
         setContentView(R.layout.activity_explorer)
     }
 
-    protected open fun bindFileOperationService(){
+    protected open fun bindFileOperationService() {
-        Intent(this, FileOperationService::class.java).also {
+        FileOperationService.bind(this) {
-            bindService(it, object : ServiceConnection {
+            fileOperationService = it
-                override fun onServiceConnected(className: ComponentName, service: IBinder) {
-                    val binder = service as FileOperationService.LocalBinder
-                    fileOperationService = binder.getService()
-                }
-                override fun onServiceDisconnected(arg0: ComponentName) {}
-            }, Context.BIND_AUTO_CREATE)
         }
     }
 

app/src/main/java/sushi/hardcore/droidfs/file_operations/FileOperationNotification.kt

@@ -1,5 +0,0 @@
-package sushi.hardcore.droidfs.file_operations
-
-import androidx.core.app.NotificationCompat
-
-class FileOperationNotification(val notificationBuilder: NotificationCompat.Builder, val notificationId: Int)

app/src/main/java/sushi/hardcore/droidfs/file_operations/FileOperationService.kt

@@ -1,65 +1,191 @@
 package sushi.hardcore.droidfs.file_operations
 
+import android.Manifest
+import android.annotation.SuppressLint
+import android.app.Notification
 import android.app.NotificationChannel
 import android.app.NotificationManager
 import android.app.PendingIntent
 import android.app.Service
+import android.content.ComponentName
+import android.content.Context
 import android.content.Intent
+import android.content.ServiceConnection
+import android.content.pm.PackageManager
+import android.content.pm.ServiceInfo
 import android.net.Uri
 import android.os.Binder
 import android.os.Build
 import android.os.Bundle
 import android.os.IBinder
+import android.provider.Settings
+import android.util.Log
+import androidx.activity.result.ActivityResultLauncher
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.core.app.NotificationCompat
 import androidx.core.app.NotificationManagerCompat
+import androidx.core.app.ServiceCompat
+import androidx.core.content.ContextCompat
 import androidx.documentfile.provider.DocumentFile
 import kotlinx.coroutines.CancellationException
-import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Deferred
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.MainScope
 import kotlinx.coroutines.async
 import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import kotlinx.coroutines.yield
+import sushi.hardcore.droidfs.BaseActivity
 import sushi.hardcore.droidfs.Constants
 import sushi.hardcore.droidfs.R
 import sushi.hardcore.droidfs.VolumeManager
 import sushi.hardcore.droidfs.VolumeManagerApp
 import sushi.hardcore.droidfs.explorers.ExplorerElement
 import sushi.hardcore.droidfs.filesystems.EncryptedVolume
+import sushi.hardcore.droidfs.filesystems.Stat
 import sushi.hardcore.droidfs.util.ObjRef
 import sushi.hardcore.droidfs.util.PathUtils
 import sushi.hardcore.droidfs.util.Wiper
+import sushi.hardcore.droidfs.widgets.CustomAlertDialogBuilder
 import java.io.File
 import java.io.FileNotFoundException
+import kotlin.coroutines.resume
+import kotlin.coroutines.suspendCoroutine
 
+/**
+ * Foreground service for file operations.
+ *
+ * Clients **must** bind to it using the [bind] method.
+ *
+ * This implementation is not thread-safe. It must only be called from the main UI thread.
+ */
 class FileOperationService : Service() {
-    companion object {
-        const val NOTIFICATION_CHANNEL_ID = "FileOperations"
-        const val ACTION_CANCEL = "file_operation_cancel"
-    }
-
-    private val binder = LocalBinder()
-    private lateinit var volumeManger: VolumeManager
-    private var serviceScope = MainScope()
-    private lateinit var notificationManager: NotificationManagerCompat
-    private val tasks = HashMap<Int, Job>()
-    private var lastNotificationId = 0
 
     inner class LocalBinder : Binder() {
         fun getService(): FileOperationService = this@FileOperationService
     }
 
-    override fun onBind(p0: Intent?): IBinder {
+    inner class PendingTask<T>(
-        volumeManger = (application as VolumeManagerApp).volumeManager
+        val title: Int,
-        return binder
+        val total: Int?,
+        private val getTask: (Int) -> Deferred<T>,
+        private val onStart: (taskId: Int, job: Deferred<T>) -> Unit,
+    ) {
+        fun start(taskId: Int): Deferred<T> = getTask(taskId).also { onStart(taskId, it) }
     }
 
-    private fun showNotification(message: Int, total: Int?): FileOperationNotification {
+    companion object {
-        ++lastNotificationId
+        const val TAG = "FileOperationService"
-        if (!::notificationManager.isInitialized){
+        const val NOTIFICATION_CHANNEL_ID = "FileOperations"
+        const val ACTION_CANCEL = "file_operation_cancel"
+
+        /**
+         * Bind to the service.
+         *
+         * Registers an [ActivityResultLauncher] in the provided activity to request notification permission. Consequently, the activity must not yet be started.
+         *
+         * The activity must stay running while calling the service's methods.
+         *
+         * If multiple activities bind simultaneously, only the latest one will be used by the service.
+         */
+        fun bind(activity: BaseActivity, onBound: (FileOperationService) -> Unit) {
+            var service: FileOperationService? = null
+            val launcher = activity.registerForActivityResult(ActivityResultContracts.RequestPermission()) { granted ->
+                if (granted) {
+                    service!!.processPendingTask()
+                } else {
+                    CustomAlertDialogBuilder(activity, activity.theme)
+                        .setTitle(R.string.warning)
+                        .setMessage(R.string.notification_denied_msg)
+                        .setPositiveButton(R.string.settings) { _, _ ->
+                            activity.startActivity(
+                                Intent(
+                                    Settings.ACTION_APPLICATION_DETAILS_SETTINGS,
+                                    Uri.fromParts("package", activity.packageName, null)
+                                )
+                            )
+                        }
+                        .setNegativeButton(R.string.later, null)
+                        .setOnDismissListener { service!!.processPendingTask() }
+                        .show()
+                }
+            }
+            activity.bindService(Intent(activity, FileOperationService::class.java), object : ServiceConnection {
+                override fun onServiceConnected(className: ComponentName, binder: IBinder) {
+                    onBound((binder as FileOperationService.LocalBinder).getService().also {
+                        it.notificationPermissionLauncher = launcher
+                        service = it
+                    })
+                }
+                override fun onServiceDisconnected(arg0: ComponentName) {}
+            }, Context.BIND_AUTO_CREATE)
+        }
+    }
+
+    private var isStarted = false
+    private val binder = LocalBinder()
+    private lateinit var volumeManger: VolumeManager
+    private var serviceScope = MainScope()
+    private lateinit var notificationPermissionLauncher: ActivityResultLauncher<String>
+    private var askForNotificationPermission = true
+    private lateinit var notificationManager: NotificationManagerCompat
+    private val notifications = HashMap<Int, NotificationCompat.Builder>()
+    private var foregroundNotificationId = -1
+    private val tasks = HashMap<Int, Job>()
+    private var newTaskId = 1
+    private var pendingTask: PendingTask<*>? = null
+
+    override fun onCreate() {
+        volumeManger = (application as VolumeManagerApp).volumeManager
+    }
+
+    override fun onBind(p0: Intent?): IBinder = binder
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        startPendingTask { id, notification ->
+            // on service start, the pending task is the foreground task
+            setForeground(id, notification)
+        }
+        isStarted = true
+        return START_NOT_STICKY
+    }
+
+    override fun onDestroy() {
+        isStarted = false
+    }
+
+    private fun processPendingTask() {
+        if (isStarted) {
+            startPendingTask { id, notification ->
+                if (foregroundNotificationId == -1) {
+                    // service started but not in foreground yet
+                    setForeground(id, notification)
+                } else {
+                    // already running in foreground, just add a new notification
+                    notificationManager.notify(id, notification)
+                }
+            }
+        } else {
+            ContextCompat.startForegroundService(
+                this,
+                Intent(this, FileOperationService::class.java)
+            )
+        }
+    }
+
+    /**
+     * Start the pending task and create an associated notification.
+     */
+    private fun startPendingTask(showNotification: (id: Int, Notification) -> Unit) {
+        val task = pendingTask
+        pendingTask = null
+        if (task == null) {
+            Log.w(TAG, "Started without pending task")
+            return
+        }
+        if (!::notificationManager.isInitialized) {
             notificationManager = NotificationManagerCompat.from(this)
         }
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
@@ -72,8 +198,7 @@ class FileOperationService : Service() {
             )
         }
         val notificationBuilder = NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID)
-        notificationBuilder
+            .setContentTitle(getString(task.title))
-                .setContentTitle(getString(message))
             .setSmallIcon(R.drawable.ic_notification)
             .setOngoing(true)
             .addAction(NotificationCompat.Action(
@@ -81,78 +206,165 @@ class FileOperationService : Service() {
                 getString(R.string.cancel),
                 PendingIntent.getBroadcast(
                     this,
-                        0,
+                    newTaskId,
                     Intent(this, NotificationBroadcastReceiver::class.java).apply {
-                            val bundle = Bundle()
+                        putExtra("bundle", Bundle().apply {
-                            bundle.putBinder("binder", LocalBinder())
+                            putBinder("binder", LocalBinder())
-                            bundle.putInt("notificationId", lastNotificationId)
+                            putInt("taskId", newTaskId)
-                            putExtra("bundle", bundle)
+                        })
                         action = ACTION_CANCEL
                     },
-                        PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
+                    PendingIntent.FLAG_IMMUTABLE
                 )
             ))
-        if (total != null) {
+        if (task.total != null) {
             notificationBuilder
-                .setContentText("0/$total")
+                .setContentText("0/${task.total}")
-                .setProgress(total, 0, false)
+                .setProgress(task.total, 0, false)
         } else {
             notificationBuilder
                 .setContentText(getString(R.string.discovering_files))
                 .setProgress(0, 0, true)
         }
-        notificationManager.notify(lastNotificationId, notificationBuilder.build())
+        showNotification(newTaskId, notificationBuilder.build())
-        return FileOperationNotification(notificationBuilder, lastNotificationId)
+        notifications[newTaskId] = notificationBuilder
+        tasks[newTaskId] = task.start(newTaskId)
+        newTaskId++
     }
 
-    private fun updateNotificationProgress(notification: FileOperationNotification, progress: Int, total: Int){
+    private fun setForeground(id: Int, notification: Notification) {
-        notification.notificationBuilder
+        ServiceCompat.startForeground(this, id, notification,
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
+                ServiceInfo.FOREGROUND_SERVICE_TYPE_DATA_SYNC
+            } else {
+                0
+            }
+        )
+        foregroundNotificationId = id
+    }
+
+    private fun updateNotificationProgress(taskId: Int, progress: Int, total: Int) {
+        val notificationBuilder = notifications[taskId] ?: return
+        notificationBuilder
                 .setProgress(total, progress, false)
                 .setContentText("$progress/$total")
-        notificationManager.notify(notification.notificationId, notification.notificationBuilder.build())
+        notificationManager.notify(taskId, notificationBuilder.build())
     }
 
-    private fun cancelNotification(notification: FileOperationNotification){
+    fun cancelOperation(taskId: Int) {
-        notificationManager.cancel(notification.notificationId)
+        tasks[taskId]?.cancel()
-    }
-
-    fun cancelOperation(notificationId: Int){
-        tasks[notificationId]?.cancel()
     }
 
     private fun getEncryptedVolume(volumeId: Int): EncryptedVolume {
         return volumeManger.getVolume(volumeId) ?: throw IllegalArgumentException("Invalid volumeId: $volumeId")
     }
 
-    private suspend fun <T> waitForTask(notification: FileOperationNotification, task: Deferred<T>): TaskResult<out T> {
+    /**
-        tasks[notification.notificationId] = task
+     *  Wait on a task, returning the appropriate [TaskResult].
+     *
+     *  This method also performs cleanup and foreground state management so it must be always used.
+     */
+    private suspend fun <T> waitForTask(
+        taskId: Int,
+        task: Deferred<T>,
+        onCancelled: (suspend () -> Unit)?,
+    ): TaskResult<out T> {
         return coroutineScope {
             withContext(serviceScope.coroutineContext) {
                 try {
                     TaskResult.completed(task.await())
                 } catch (e: CancellationException) {
+                    onCancelled?.invoke()
                     TaskResult.cancelled()
                 } catch (e: Throwable) {
                     e.printStackTrace()
                     TaskResult.error(e.localizedMessage)
                 } finally {
-                    cancelNotification(notification)
+                    notificationManager.cancel(taskId)
+                    notifications.remove(taskId)
+                    tasks.remove(taskId)
+                    if (tasks.size == 0) {
+                        // last task finished, remove from foreground state but don't stop the service
+                        ServiceCompat.stopForeground(this@FileOperationService, ServiceCompat.STOP_FOREGROUND_REMOVE)
+                        foregroundNotificationId = -1
+                    } else if (taskId == foregroundNotificationId) {
+                        // foreground task finished, falling back to the next one
+                        val entry = notifications.entries.first()
+                        setForeground(entry.key, entry.value.build())
+                    }
                 }
             }
         }
     }
 
-    private suspend fun <T> volumeTask(
+    /**
-        volumeId: Int,
+     * Create and run a new task until completion.
-        notification: FileOperationNotification,
+     *
-        task: suspend (encryptedVolume: EncryptedVolume) -> T
+     * Handles notification permission request, service startup and notification management.
+     *
+     * Overrides [pendingTask] without checking! (safe if user is not insanely fast)
+     */
+    private suspend fun <T> newTask(
+        title: Int,
+        total: Int?,
+        getTask: (taskId: Int) -> Deferred<T>,
+        onCancelled: (suspend () -> Unit)?,
     ): TaskResult<out T> {
-        return waitForTask(
+        val startedTask = suspendCoroutine { continuation ->
-            notification,
+            val task = PendingTask(title, total, getTask) { taskId, job ->
-            volumeManger.getCoroutineScope(volumeId).async {
+                continuation.resume(Pair(taskId, job))
-                task(getEncryptedVolume(volumeId))
             }
-        )
+            pendingTask = task
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+                if (
+                    ContextCompat.checkSelfPermission(
+                        this,
+                        Manifest.permission.POST_NOTIFICATIONS
+                    ) != PackageManager.PERMISSION_GRANTED
+                    && askForNotificationPermission
+                ) {
+                    notificationPermissionLauncher.launch(Manifest.permission.POST_NOTIFICATIONS)
+                    askForNotificationPermission = false // only ask once per service instance
+                    return@suspendCoroutine
+                }
+            }
+            processPendingTask()
+        }
+        return waitForTask(startedTask.first, startedTask.second, onCancelled)
+    }
+
+    private suspend fun <T> volumeTask(
+        title: Int,
+        total: Int?,
+        volumeId: Int,
+        task: suspend (taskId: Int, encryptedVolume: EncryptedVolume) -> T
+    ): TaskResult<out T> {
+        return newTask(title, total, { taskId ->
+            volumeManger.getCoroutineScope(volumeId).async {
+                task(taskId, getEncryptedVolume(volumeId))
+            }
+        }, null)
+    }
+
+    private suspend fun <T> globalTask(
+        title: Int,
+        total: Int?,
+        task: suspend (taskId: Int) -> T,
+        onCancelled: (suspend () -> Unit)? = null,
+    ): TaskResult<out T> {
+        return newTask(title, total, { taskId ->
+            serviceScope.async(Dispatchers.IO) {
+                task(taskId)
+            }
+        }, if (onCancelled == null) {
+            null
+        } else {
+            {
+                serviceScope.launch(Dispatchers.IO) {
+                    onCancelled()
+                }
+            }
+        })
     }
 
     private suspend fun copyFile(
@@ -196,9 +408,8 @@ class FileOperationService : Service() {
         items: List<OperationFile>,
         srcVolumeId: Int = volumeId,
     ): TaskResult<out String?> {
-        val notification = showNotification(R.string.file_op_copy_msg, items.size)
         val srcEncryptedVolume = getEncryptedVolume(srcVolumeId)
-        return volumeTask(volumeId, notification) { encryptedVolume ->
+        return volumeTask(R.string.file_op_copy_msg, items.size, volumeId) { taskId, encryptedVolume ->
             var failedItem: String? = null
             for (i in items.indices) {
                 yield()
@@ -212,7 +423,7 @@ class FileOperationService : Service() {
                     failedItem = items[i].srcPath
                 }
                 if (failedItem == null) {
-                    updateNotificationProgress(notification, i+1, items.size)
+                    updateNotificationProgress(taskId, i+1, items.size)
                 } else {
                     break
                 }
@@ -222,8 +433,7 @@ class FileOperationService : Service() {
     }
 
     suspend fun moveElements(volumeId: Int, toMove: List<OperationFile>, toClean: List<String>): TaskResult<out String?> {
-        val notification = showNotification(R.string.file_op_move_msg, toMove.size)
+        return volumeTask(R.string.file_op_move_msg, toMove.size, volumeId) { taskId, encryptedVolume ->
-        return volumeTask(volumeId, notification) { encryptedVolume ->
             val total = toMove.size+toClean.size
             var failedItem: String? = null
             for ((i, item) in toMove.withIndex()) {
@@ -231,7 +441,7 @@ class FileOperationService : Service() {
                     failedItem = item.srcPath
                     break
                 } else {
-                    updateNotificationProgress(notification, i+1, total)
+                    updateNotificationProgress(taskId, i+1, total)
                 }
             }
             if (failedItem == null) {
@@ -240,7 +450,7 @@ class FileOperationService : Service() {
                         failedItem = folderPath
                         break
                     } else {
-                        updateNotificationProgress(notification, toMove.size+i+1, total)
+                        updateNotificationProgress(taskId, toMove.size+i+1, total)
                     }
                 }
             }
@@ -252,7 +462,7 @@ class FileOperationService : Service() {
         encryptedVolume: EncryptedVolume,
         dstPaths: List<String>,
         uris: List<Uri>,
-        notification: FileOperationNotification,
+        taskId: Int,
     ): String? {
         var failedIndex = -1
         for (i in dstPaths.indices) {
@@ -265,7 +475,7 @@ class FileOperationService : Service() {
                 failedIndex = i
             }
             if (failedIndex == -1) {
-                updateNotificationProgress(notification, i+1, dstPaths.size)
+                updateNotificationProgress(taskId, i+1, dstPaths.size)
             } else {
                 return uris[failedIndex].toString()
             }
@@ -274,9 +484,8 @@ class FileOperationService : Service() {
     }
 
     suspend fun importFilesFromUris(volumeId: Int, dstPaths: List<String>, uris: List<Uri>): TaskResult<out String?> {
-        val notification = showNotification(R.string.file_op_import_msg, dstPaths.size)
+        return volumeTask(R.string.file_op_import_msg, dstPaths.size, volumeId) { taskId, encryptedVolume ->
-        return volumeTask(volumeId, notification) { encryptedVolume ->
+            importFilesFromUris(encryptedVolume, dstPaths, uris, taskId)
-            importFilesFromUris(encryptedVolume, dstPaths, uris, notification)
         }
     }
 
@@ -284,8 +493,6 @@ class FileOperationService : Service() {
      * Map the content of an unencrypted directory to prepare its import
      *
      * Contents of dstFiles and srcUris, at the same index, will match each other
-     *
-     * @return false if cancelled early, true otherwise.
      */
     private suspend fun recursiveMapDirectoryForImport(
         rootSrcDir: DocumentFile,
@@ -316,36 +523,35 @@ class FileOperationService : Service() {
         rootDstPath: String,
         rootSrcDir: DocumentFile,
     ): ImportDirectoryResult {
-        val notification = showNotification(R.string.file_op_import_msg, null)
         val srcUris = arrayListOf<Uri>()
-        return ImportDirectoryResult(volumeTask(volumeId, notification) { encryptedVolume ->
+        return ImportDirectoryResult(volumeTask(R.string.file_op_import_msg, null, volumeId) { taskId, encryptedVolume ->
             var failedItem: String? = null
             val dstFiles = arrayListOf<String>()
             val dstDirs = arrayListOf<String>()
             recursiveMapDirectoryForImport(rootSrcDir, rootDstPath, dstFiles, srcUris, dstDirs)
             // create destination folders so the new files can use them
             for (dir in dstDirs) {
-                if (!encryptedVolume.mkdir(dir)) {
+                // if directory creation fails, check if it was already present
+                if (!encryptedVolume.mkdir(dir) && encryptedVolume.getAttr(dir)?.type != Stat.S_IFDIR) {
                     failedItem = dir
                     break
                 }
             }
             if (failedItem == null) {
-                failedItem = importFilesFromUris(encryptedVolume, dstFiles, srcUris, notification)
+                failedItem = importFilesFromUris(encryptedVolume, dstFiles, srcUris, taskId)
             }
             failedItem
         }, srcUris)
     }
 
     suspend fun wipeUris(uris: List<Uri>, rootFile: DocumentFile? = null): TaskResult<out String?> {
-        val notification = showNotification(R.string.file_op_wiping_msg, uris.size)
+        return globalTask(R.string.file_op_wiping_msg, uris.size, { taskId ->
-        val task = serviceScope.async(Dispatchers.IO) {
             var errorMsg: String? = null
             for (i in uris.indices) {
                 yield()
                 errorMsg = Wiper.wipe(this@FileOperationService, uris[i])
                 if (errorMsg == null) {
-                    updateNotificationProgress(notification, i+1, uris.size)
+                    updateNotificationProgress(taskId, i+1, uris.size)
                 } else {
                     break
                 }
@@ -354,8 +560,7 @@ class FileOperationService : Service() {
                 rootFile?.delete()
             }
             errorMsg
-        }
+        })
-        return waitForTask(notification, task)
     }
 
     private fun exportFileInto(encryptedVolume: EncryptedVolume, srcPath: String, treeDocumentFile: DocumentFile): Boolean {
@@ -391,8 +596,7 @@ class FileOperationService : Service() {
     }
 
     suspend fun exportFiles(volumeId: Int, items: List<ExplorerElement>, uri: Uri): TaskResult<out String?> {
-        val notification = showNotification(R.string.file_op_export_msg, items.size)
+        return volumeTask(R.string.file_op_export_msg, items.size, volumeId) { taskId, encryptedVolume ->
-        return volumeTask(volumeId, notification) { encryptedVolume ->
             val treeDocumentFile = DocumentFile.fromTreeUri(this@FileOperationService, uri)!!
             var failedItem: String? = null
             for (i in items.indices) {
@@ -407,7 +611,7 @@ class FileOperationService : Service() {
                     }
                 }
                 if (failedItem == null) {
-                    updateNotificationProgress(notification, i+1, items.size)
+                    updateNotificationProgress(taskId, i+1, items.size)
                 } else {
                     break
                 }
@@ -436,8 +640,7 @@ class FileOperationService : Service() {
     }
 
     suspend fun removeElements(volumeId: Int, items: List<ExplorerElement>): String? {
-        val notification = showNotification(R.string.file_op_delete_msg, items.size)
+        return volumeTask(R.string.file_op_delete_msg, items.size, volumeId) { taskId, encryptedVolume ->
-        return volumeTask(volumeId, notification) { encryptedVolume ->
             var failedItem: String? = null
             for ((i, element) in items.withIndex()) {
                 yield()
@@ -447,7 +650,7 @@ class FileOperationService : Service() {
                     failedItem = element.fullPath
                 }
                 if (failedItem == null) {
-                    updateNotificationProgress(notification, i + 1, items.size)
+                    updateNotificationProgress(taskId, i + 1, items.size)
                 } else {
                     break
                 }
@@ -456,13 +659,13 @@ class FileOperationService : Service() {
         }.failedItem // treat cancellation as success
     }
 
-    private suspend fun recursiveCountChildElements(rootDirectory: DocumentFile, scope: CoroutineScope): Int {
+    private suspend fun recursiveCountChildElements(rootDirectory: DocumentFile): Int {
         yield()
         val children = rootDirectory.listFiles()
         var count = children.size
         for (child in children) {
             if (child.isDirectory) {
-                count += recursiveCountChildElements(child, scope)
+                count += recursiveCountChildElements(child)
             }
         }
         return count
@@ -472,9 +675,8 @@ class FileOperationService : Service() {
         src: DocumentFile,
         dst: DocumentFile,
         dstRootDirectory: ObjRef<DocumentFile?>?,
-        notification: FileOperationNotification,
+        taskId: Int,
         total: Int,
-        scope: CoroutineScope,
         progress: ObjRef<Int> = ObjRef(0)
     ): DocumentFile? {
         val dstDir = dst.createDirectory(src.name ?: return src) ?: return src
@@ -491,10 +693,10 @@ class FileOperationService : Service() {
                 inputStream.close()
                 if (written != child.length()) return child
             } else {
-                recursiveCopyVolume(child, dstDir, null, notification, total, scope, progress)?.let { return it }
+                recursiveCopyVolume(child, dstDir, null, taskId, total, progress)?.let { return it }
             }
             progress.value++
-            updateNotificationProgress(notification, progress.value, total)
+            updateNotificationProgress(taskId, progress.value, total)
         }
         return null
     }
@@ -502,13 +704,14 @@ class FileOperationService : Service() {
     class CopyVolumeResult(val taskResult: TaskResult<out DocumentFile?>, val dstRootDirectory: DocumentFile?)
 
     suspend fun copyVolume(src: DocumentFile, dst: DocumentFile): CopyVolumeResult {
-        val notification = showNotification(R.string.copy_volume_notification, null)
         val dstRootDirectory = ObjRef<DocumentFile?>(null)
-        val task = serviceScope.async(Dispatchers.IO) {
+        val result = globalTask(R.string.copy_volume_notification, null, { taskId ->
-            val total = recursiveCountChildElements(src, this)
+            val total = recursiveCountChildElements(src)
-            updateNotificationProgress(notification, 0, total)
+            updateNotificationProgress(taskId, 0, total)
-            recursiveCopyVolume(src, dst, dstRootDirectory, notification, total, this)
+            recursiveCopyVolume(src, dst, dstRootDirectory, taskId, total)
-        }
+        }, {
-        return CopyVolumeResult(waitForTask(notification, task), dstRootDirectory.value)
+            dstRootDirectory.value?.delete()
+        })
+        return CopyVolumeResult(result, dstRootDirectory.value)
     }
 }

app/src/main/java/sushi/hardcore/droidfs/file_operations/NotificationBroadcastReceiver.kt

@@ -6,13 +6,11 @@ import android.content.Intent
 
 class NotificationBroadcastReceiver: BroadcastReceiver() {
     override fun onReceive(context: Context, intent: Intent) {
-        if (intent.action == FileOperationService.ACTION_CANCEL){
+        if (intent.action == FileOperationService.ACTION_CANCEL) {
             intent.getBundleExtra("bundle")?.let { bundle ->
-                (bundle.getBinder("binder") as FileOperationService.LocalBinder?)?.let { binder ->
+                // TODO: use peekService instead?
-                    val notificationId = bundle.getInt("notificationId")
+                val binder = (bundle.getBinder("binder") as FileOperationService.LocalBinder?)
-                    val service = binder.getService()
+                binder?.getService()?.cancelOperation(bundle.getInt("taskId"))
-                    service.cancelOperation(notificationId)
-                }
             }
         }
     }

app/src/main/res/values/strings.xml

@@ -279,4 +279,6 @@
     <string name="debug">Debug</string>
     <string name="logcat_title">DroidFS Logcat</string>
     <string name="logcat_saved">Logcat saved</string>
+    <string name="later">Later</string>
+    <string name="notification_denied_msg">Notification permission has been denied. Background file operations won\'t be visible. You can change this in the app\'s permission settings.</string>
 </resources>