Trasferimento di dati avviato dall'utente

If you need to perform a data transfer that may take a long time, you can create a JobScheduler job and identify it as a user-initiated data transfer (UIDT) job. UIDT jobs are intended for longer-duration data transfers that are initiated by the device user, such as downloading a file from a remote server. UIDT jobs were introduced with Android 14 (API level 34).

User-initiated data transfer jobs are started by the user. These jobs require a notification, start immediately, and may be able to run for an extended period of time as system conditions allow. You can run several user-initiated data transfer jobs concurrently.

User initiated jobs must be scheduled while the application is visible to the user (or in one of the allowed conditions). After all constraints are met, user initiated jobs can be executed by the OS, subject to system health restrictions. The system may also use the provided estimated payload size to determine how long the job executes.

Pianificare i job di trasferimento di dati avviati dall'utente

Per eseguire un job di trasferimento di dati avviato dall'utente:

  1. Assicurati che la tua app abbia dichiarato JobService e le autorizzazioni associate nel manifest:

    <service android:name="com.example.app.CustomTransferService"
        android:permission="android.permission.BIND_JOB_SERVICE"
        android:exported="false">
        ...
</service>

    Inoltre, definisci una sottoclasse concreta di JobService per il trasferimento dei dati:

    Kotlin

    class CustomTransferService : JobService() {
  ...
}

    Java

    class CustomTransferService extends JobService() {

    ....

}

  2. Dichiara l'autorizzazione RUN_USER_INITIATED_JOBS nel manifest:

    <manifest ...>
    <uses-permission android:name="android.permission.RUN_USER_INITIATED_JOBS" />
    <application ...>
        ...
    </application>
</manifest>

  3. Chiama il metodo setUserInitiated() durante la creazione di un oggetto JobInfo. (Questo metodo è disponibile a partire da Android 14.) Ti consigliamo inoltre di fornire una stima delle dimensioni del payload chiamando il numero setEstimatedNetworkBytes() durante la creazione del lavoro.

    Kotlin

    val networkRequestBuilder = NetworkRequest.Builder()
        // Add or remove capabilities based on your requirements.
        // For example, this code specifies that the job won't run
        // unless there's a connection to the internet (not just a local
        // network), and the connection doesn't charge per-byte.
        .addCapability(NET_CAPABILITY_INTERNET)
        .addCapability(NET_CAPABILITY_NOT_METERED)
        .build()

val jobInfo = JobInfo.Builder(jobId,
              ComponentName(mContext, CustomTransferService::class.java))
        // ...
        .setUserInitiated(true)
        .setRequiredNetwork(networkRequestBuilder)
        // Provide your estimate of the network traffic here
        .setEstimatedNetworkBytes(1024 * 1024 * 1024)
        // ...
        .build()

    Java

    NetworkRequest networkRequest = new NetworkRequest.Builder()
    // Add or remove capabilities based on your requirements.
    // For example, this code specifies that the job won't run
    // unless there's a connection to the internet (not just a local
    // network), and the connection doesn't charge per-byte.
    .addCapability(NET_CAPABILITY_INTERNET)
    .addCapability(NET_CAPABILITY_NOT_METERED)
    .build();

JobInfo jobInfo = JobInfo.Builder(jobId,
        new ComponentName(mContext, CustomTransferService.class))
    // ...
    .setUserInitiated(true)
    .setRequiredNetwork(networkRequest)
    // Provide your estimate of the network traffic here
    .setEstimatedNetworkBytes(1024 * 1024 * 1024)
    // ...
    .build();

  4. Mentre il job è in esecuzione, chiama setNotification() sull'oggetto JobService. Chiamata setNotification() informa l'utente che il job è in esecuzione, sia in Gestione attività sia nell'area di notifica della barra di stato.

    Al termine dell'esecuzione, chiama jobFinished() per segnalare al sistema che il job è completato o che deve essere riprogrammato.

    Kotlin

    class CustomTransferService: JobService() {
    private val scope = CoroutineScope(Dispatchers.IO)

    @RequiresApi(Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
    override fun onStartJob(params: JobParameters): Boolean {
        val notification = Notification.Builder(applicationContext,
                              NOTIFICATION_CHANNEL_ID)
            .setContentTitle("My user-initiated data transfer job")
            .setSmallIcon(android.R.mipmap.myicon)
            .setContentText("Job is running")
            .build()

        setNotification(params, notification.id, notification,
                JobService.JOB_END_NOTIFICATION_POLICY_DETACH)
        // Execute the work associated with this job asynchronously.
        scope.launch {
            doDownload(params)
        }
        return true
    }

    private suspend fun doDownload(params: JobParameters) {
        // Run the relevant async download task, then call
        // jobFinished once the task is completed.
        jobFinished(params, false)
    }

    // Called when the system stops the job.
    override fun onStopJob(params: JobParameters?): Boolean {
        // Asynchronously record job-related data, such as the
        // stop reason.
        return true // or return false if job should end entirely
    }
}

    Java

    class CustomTransferService extends JobService{
    @RequiresApi(Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
    @Override
    public boolean onStartJob(JobParameters params) {
        Notification notification = Notification.Builder(getBaseContext(),
                                        NOTIFICATION_CHANNEL_ID)
                .setContentTitle("My user-initiated data transfer job")
                .setSmallIcon(android.R.mipmap.myicon)
                .setContentText("Job is running")
                .build();

        setNotification(params, notification.id, notification,
                          JobService.JOB_END_NOTIFICATION_POLICY_DETACH)
        // Execute the work associated with this job asynchronously.
        new Thread(() -> doDownload(params)).start();
        return true;
    }

    private void doDownload(JobParameters params) {
        // Run the relevant async download task, then call
        // jobFinished once the task is completed.
        jobFinished(params, false);
    }

    // Called when the system stops the job.
    @Override
    public boolean onStopJob(JobParameters params) {
        // Asynchronously record job-related data, such as the
        // stop reason.
        return true; // or return false if job should end entirely
    }
}

  5. Aggiorna periodicamente la notifica per tenere informato l'utente sullo stato e sull'avanzamento del job. Se non riesci a determinare le dimensioni del trasferimento prima di pianificare il job o devi aggiornare le dimensioni stimate del trasferimento, utilizza la nuova API updateEstimatedNetworkBytes() per aggiornare le dimensioni del trasferimento dopo che sono state determinate.

Consigli

Per eseguire in modo efficace i job UIDT:

  1. Definisci chiaramente i vincoli di rete e di esecuzione del job per specificare quando deve essere eseguito.

  2. Esegui l'attività in modo asincrono in onStartJob(); ad esempio, puoi farlo utilizzando una coroutine. Se non esegui l'attività in modo asincrono, il lavoro viene eseguito sul thread principale e potrebbe bloccarlo, causando un errore ANR.

  3. Per evitare di eseguire il job più a lungo del necessario, chiama jobFinished() al termine del trasferimento, indipendentemente dal fatto che vada a buon fine o meno. In questo modo, il job non viene eseguito più a lungo del necessario. Per scoprire perché un job è stato interrotto, implementa il metodo di callback onStopJob() e chiama JobParameters.getStopReason().

Compatibilità con le versioni precedenti

Al momento non esiste una libreria Jetpack che supporti i job UIDT. Per questo motivo, ti consigliamo di proteggere la modifica con codice che verifichi che stai utilizzando Android 14 o versioni successive. Nelle versioni precedenti di Android, puoi utilizzare l'implementazione del servizio in primo piano di WorkManager come approccio di riserva.

Ecco un esempio di codice che verifica la versione di sistema appropriata:

Kotlin

fun beginTask() {
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.UPSIDE_DOWN_CAKE) {
        scheduleDownloadFGSWorker(context)
    } else {
        scheduleDownloadUIDTJob(context)
    }
}

private fun scheduleDownloadUIDTJob(context: Context) {
    // build jobInfo
    val jobScheduler: JobScheduler =
        context.getSystemService(Context.JOB_SCHEDULER_SERVICE) as JobScheduler
    jobScheduler.schedule(jobInfo)
}

private fun scheduleDownloadFGSWorker(context: Context) {
    val myWorkRequest = OneTimeWorkRequest.from(DownloadWorker::class.java)
    WorkManager.getInstance(context).enqueue(myWorkRequest)
}

Java

public void beginTask() {
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.UPSIDE_DOWN_CAKE) {
        scheduleDownloadFGSWorker(context);
    } else {
        scheduleDownloadUIDTJob(context);
    }
}

private void scheduleDownloadUIDTJob(Context context) {
    // build jobInfo
    JobScheduler jobScheduler =
            (JobScheduler) context.getSystemService(Context.JOB_SCHEDULER_SERVICE);
    jobScheduler.schedule(jobInfo);
}

private void scheduleDownloadFGSWorker(Context context) {
    OneTimeWorkRequest myWorkRequest = OneTimeWorkRequest.from(DownloadWorker.class);
    WorkManager.getInstance(context).enqueue(myWorkRequest)
}

Arresta i job UIDT

Both the user and the system can stop user-initiated transfer jobs.

Dall'utente, da Task Manager

The user can stop a user-initiated data transfer job that appears in the Task Manager.

At the moment that the user presses Stop, the system does the following:

  • Terminates your app's process immediately, including all other jobs or foreground services running.
  • Doesn't call onStopJob() for any running jobs.
  • Prevents user-visible jobs from being rescheduled.

For these reasons, it's recommended to provide controls in the notification posted for the job to allow gracefully stopping and rescheduling the job.

Note that, under special circumstances, the Stop button doesn't appear next to the job in the Task Manager, or the job isn't shown in the Task Manager at all.

Dal sistema

Unlike regular jobs, user-initiated data transfer jobs are unaffected by App Standby Buckets quotas. However, the system still stops the job if any of the following conditions occur:

  • A developer-defined constraint is no longer met.
  • The system determines that the job has run for longer than necessary to complete the data transfer task.
  • The system needs to prioritize system health and stop jobs due to increased thermal state.
  • The app process is killed due to low device memory.

When the job is stopped by the system for reasons other than low device memory, the system calls onStopJob(), and the system retries the job at a time that the system deems to be optimal. Make sure that your app can persist the data transfer state even if onStopJob() isn't called, and that your app can restore this state when onStartJob() is called again.

Condizioni consentite per la pianificazione dei job di trasferimento di dati avviati dall'utente

Apps can only start a user-initiated data transfer job if the app is in the visible window, or if certain conditions are met:

  • If an app can launch activities from the background, it can also launch user-initiated data transfer jobs from the background.
  • If an app has an activity in the back stack of an existing task on the Recents screen, that alone doesn't allow a user-initiated data transfer job to run.

If the job is scheduled to run at a time when the necessary conditions are not met, the job fails and returns a RESULT_FAILURE error code.

Vincoli consentiti per i processi di trasferimento di dati avviati dall'utente

To support jobs running at optimal points, Android offers the ability to assign constraints to each job type. These constraints are available as of Android 13.

Note: The following table only compares the constraints that vary between each job type. See JobScheduler developer page or work constraints for all constraints.

The following table shows the different job types that support a given job constraint, as well as the set of job constraints that WorkManager supports. Use the search bar before the table to filter the table by the name of a job constraint method.

These are the constraints allowed with user-initiated data transfer jobs:

  • setBackoffCriteria(JobInfo.BACKOFF_POLICY_EXPONENTIAL)
  • setClipData()
  • setEstimatedNetworkBytes()
  • setMinimumNetworkChunkBytes()
  • setPersisted()
  • setNamespace()
  • setRequiredNetwork()
  • setRequiredNetworkType()
  • setRequiresBatteryNotLow()
  • setRequiresCharging()
  • setRequiresStorageNotLow()

Test

Nell'elenco che segue vengono mostrati alcuni passaggi per testare manualmente i job dell'app:

  • Per ottenere l'ID job, recupera il valore definito al momento della creazione del job.

  • Per eseguire immediatamente un job o per riprovare un job interrotto, esegui questo comando: in una finestra del terminale:

    adb shell cmd jobscheduler run -f APP_PACKAGE_NAME JOB_ID

  • Per simulare il sistema che forza l'arresto di un job (a causa dell'integrità del sistema o condizioni fuori quota), esegui questo comando in una finestra del terminale:

    adb shell cmd jobscheduler timeout TEST_APP_PACKAGE TEST_JOB_ID

Vedi anche

Risorse aggiuntive

Per ulteriori informazioni sui trasferimenti di dati avviati dall'utente, consulta le seguenti risorse aggiuntive: