Support for long-running workers

WorkManager 2.3.0-alpha02 adds first-class support for long running workers. In such cases, WorkManager can provide a signal to the OS that the process should be kept alive if possible while this work is executing. These Workers can run longer than 10 minutes. Example use-cases for this new feature include bulk uploads or downloads (that cannot be chunked), crunching on an ML model locally, or a task that's important to the user of the app.

Under the hood, WorkManager manages and runs a foreground service on your behalf to execute the WorkRequest, while also showing a configurable notification.

ListenableWorker now supports the setForegroundAsync() API, and CoroutineWorker supports a suspending setForeground() API. These APIs allow developers to specify that this WorkRequest is important (from a user perspective) or long-running.

Starting with 2.3.0-alpha03, WorkManager also allows you to create a PendingIntent, which can be used to cancel workers without having to register a new Android component using the createCancelPendingIntent() API. This approach is especially useful when used with the setForegroundAsync() or setForeground() APIs, which can be used to add a notification action to cancel the Worker.

Creating and managing long-running workers

You'll use a slightly different approach depending on whether you are coding in Kotlin or Java.

Java

Developers using a ListenableWorker or a Worker can call the setForegroundAsync() API, which returns a ListenableFuture<Void>. You can also call setForegroundAsync(), to update an ongoing Notification.

Here is a simple example of a long running worker that downloads a file. This Worker keeps track of progress to update an ongoing Notification which shows the download progress.

public class DownloadWorker extends Worker {
    private static final String KEY_INPUT_URL = "KEY_INPUT_URL";
    private static final String KEY_OUTPUT_FILE_NAME = "KEY_OUTPUT_FILE_NAME";

    private NotificationManager notificationManager;

    public DownloadWorker(
        @NonNull Context context,
        @NonNull WorkerParameters parameters) {
            super(context, parameters);
            notificationManager = (NotificationManager)
                context.getSystemService(NOTIFICATION_SERVICE);
    }

    @NonNull
    @Override
    public Result doWork() {
        Data inputData = getInputData();
        String inputUrl = inputData.getString(KEY_INPUT_URL);
        String outputFile = inputData.getString(KEY_OUTPUT_FILE_NAME);
        // Mark the Worker as important
        String progress = "Starting Download";
        setForegroundAsync(createForegroundInfo(progress));
        download(inputUrl, outputFile);
        return Result.success();
    }

    private void download(String inputUrl, String outputFile) {
        // Downloads a file and updates bytes read
        // Calls setForegroundInfoAsync() periodically when it needs to update
       // the ongoing Notification
    }

    @NonNull
    private ForegroundInfo createForegroundInfo(@NonNull String progress) {
        // Build a notification using bytesRead and contentLength

        Context context = getApplicationContext();
        String id = context.getString(R.string.notification_channel_id);
        String title = context.getString(R.string.notification_title);
        String cancel = context.getString(R.string.cancel_download);
        // This PendingIntent can be used to cancel the worker
        PendingIntent intent = WorkManager.getInstance(context)
                .createCancelPendingIntent(getId());

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            createChannel();
        }

        Notification notification = new NotificationCompat.Builder(context, id)
                .setContentTitle(title)
                .setTicker(title)
                .setSmallIcon(R.drawable.ic_work_notification)
                .setOngoing(true)
                // Add the cancel action to the notification which can
                // be used to cancel the worker
                .addAction(android.R.drawable.ic_delete, cancel, intent)
                .build();

        return new ForegroundInfo(notification);
    }

    @RequiresApi(Build.VERSION_CODES.O)
    private void createChannel() {
        // Create a Notification channel
    }
}

Kotlin

Kotlin developers should use CoroutineWorker. Instead of using setForegroundAsync(), you can use the suspending version of that method, setForeground().

class DownloadWorker(context: Context, parameters: WorkerParameters) :
    CoroutineWorker(context, parameters) {

    private val notificationManager =
        context.getSystemService(Context.NOTIFICATION_SERVICE) as
                NotificationManager

    override suspend fun doWork(): Result {
        val inputUrl = inputData.getString(KEY_INPUT_URL)
                       ?: return Result.failure()
        val outputFile = inputData.getString(KEY_OUTPUT_FILE_NAME)
                       ?: return Result.failure()
        // Mark the Worker as important
        val progress = "Starting Download"
        setForeground(createForegroundInfo(progress))
        download(inputUrl, outputFile)
        return Result.success()
    }

    private fun download(inputUrl: String, outputFile: String) {
        // Downloads a file and updates bytes read
        // Calls setForegroundInfo() periodically when it needs to update
        // the ongoing Notification
    }
    // Creates an instance of ForegroundInfo which can be used to update the
    // ongoing notification.
    private fun createForegroundInfo(progress: String): ForegroundInfo {
        val id = applicationContext.getString(R.string.notification_channel_id)
        val title = applicationContext.getString(R.string.notification_title)
        val cancel = applicationContext.getString(R.string.cancel_download)
        // This PendingIntent can be used to cancel the worker
        val intent = WorkManager.getInstance(applicationContext)
                .createCancelPendingIntent(getId())

        // Create a Notification channel if necessary
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            createChannel()
        }

        val notification = NotificationCompat.Builder(applicationContext, id)
            .setContentTitle(title)
            .setTicker(title)
            .setContentText(progress)
            .setSmallIcon(R.drawable.ic_work_notification)
            .setOngoing(true)
            // Add the cancel action to the notification which can
            // be used to cancel the worker
            .addAction(android.R.drawable.ic_delete, cancel, intent)
            .build()

        return ForegroundInfo(notification)
    }

    @RequiresApi(Build.VERSION_CODES.O)
    private fun createChannel() {
        // Create a Notification channel
    }

    companion object {
        const val KEY_INPUT_URL = "KEY_INPUT_URL"
        const val KEY_OUTPUT_FILE_NAME = "KEY_OUTPUT_FILE_NAME"
    }
}