ListenableWorker

public abstract class ListenableWorker
extends Object

java.lang.Object
   ↳ androidx.work.ListenableWorker

A class that can perform work asynchronously in WorkManager. For most cases, we recommend using Worker, which offers a simple synchronous API that is executed on a pre-specified background thread.

ListenableWorker classes are instantiated at runtime by the WorkerFactory specified in the Configuration. The startWork() method is called on the main thread.

In case the work is preempted and later restarted for any reason, a new instance of ListenableWorker is created. This means that startWork is called exactly once per ListenableWorker instance. A new ListenableWorker is created if a unit of work needs to be rerun.

A ListenableWorker is given a maximum of ten minutes to finish its execution and return a ListenableWorker.Result. After this time has expired, the worker will be signalled to stop and its ListenableFuture will be cancelled.

Exercise caution when renaming or removing ListenableWorkers from your codebase.

Summary

Nested classes

class ListenableWorker.Result

The result of a ListenableWorker's computation. 

Public constructors

ListenableWorker(Context appContext, WorkerParameters workerParams)

Public methods

final Context getApplicationContext()

Gets the application Context.

ListenableFuture<ForegroundInfo> getForegroundInfoAsync()

Return an instance of ForegroundInfo if the WorkRequest is important to the user.

final UUID getId()

Gets the ID of the WorkRequest that created this Worker.

final Data getInputData()

Gets the input data.

final Network getNetwork()

Gets the Network to use for this Worker.

final int getRunAttemptCount()

Gets the current run attempt count for this work.

final Set<String> getTags()

Gets a Set of tags associated with this Worker's WorkRequest.

final List<String> getTriggeredContentAuthorities()

Gets the list of content authorities that caused this Worker to execute.

final List<Uri> getTriggeredContentUris()

Gets the list of content Uris that caused this Worker to execute.

final boolean isStopped()

Returns true if this Worker has been told to stop.

void onStopped()

This method is invoked when this Worker has been told to stop.

final ListenableFuture<Void> setForegroundAsync(ForegroundInfo foregroundInfo)

This specifies that the WorkRequest is long-running or otherwise important.

ListenableFuture<Void> setProgressAsync(Data data)

Updates ListenableWorker progress.

abstract ListenableFuture<ListenableWorker.Result> startWork()

Override this method to start your actual background processing.

Inherited methods

Public constructors

ListenableWorker

public ListenableWorker (Context appContext, 
                WorkerParameters workerParams)

Parameters
appContext Context: The application Context
workerParams WorkerParameters: Parameters to setup the internal state of this worker

Public methods

getApplicationContext

public final Context getApplicationContext ()

Gets the application Context.

Returns
Context The application Context

getForegroundInfoAsync

public ListenableFuture<ForegroundInfo> getForegroundInfoAsync ()

Return an instance of ForegroundInfo if the WorkRequest is important to the user. In this case, WorkManager provides a signal to the OS that the process should be kept alive while this work is executing.

Prior to Android S, WorkManager manages and runs a foreground service on your behalf to execute the WorkRequest, showing the notification provided in the ForegroundInfo. To update this notification subsequently, the application can use NotificationManager.

Starting in Android S and above, WorkManager manages this WorkRequest using an immediate job.

Returns
ListenableFuture<ForegroundInfo> A ListenableFuture of ForegroundInfo instance if the WorkRequest is marked immediate. For more information look at WorkRequest.Builder.setExpedited(OutOfQuotaPolicy).

getId

public final UUID getId ()

Gets the ID of the WorkRequest that created this Worker.

Returns
UUID The ID of the creating WorkRequest

getInputData

public final Data getInputData ()

Gets the input data. Note that in the case that there are multiple prerequisites for this Worker, the input data has been run through an InputMerger.

Returns
Data The input data for this work

getNetwork

public final Network getNetwork ()

Gets the Network to use for this Worker. This method returns null if there is no network needed for this work request.

Returns
Network The Network specified by the OS to be used with this Worker

getRunAttemptCount

public final int getRunAttemptCount ()

Gets the current run attempt count for this work. Note that for periodic work, this value gets reset between periods.

Returns
int The current run attempt count for this work.

getTags

public final Set<String> getTags ()

Gets a Set of tags associated with this Worker's WorkRequest.

Returns
Set<String> The Set of tags associated with this Worker's WorkRequest

getTriggeredContentAuthorities

public final List<String> getTriggeredContentAuthorities ()

Gets the list of content authorities that caused this Worker to execute. See JobParameters#getTriggeredContentAuthorities() for relevant JobScheduler code.

Returns
List<String> The list of content authorities that caused this Worker to execute

getTriggeredContentUris

public final List<Uri> getTriggeredContentUris ()

Gets the list of content Uris that caused this Worker to execute. See JobParameters#getTriggeredContentUris() for relevant JobScheduler code.

Returns
List<Uri> The list of content Uris that caused this Worker to execute

isStopped

public final boolean isStopped ()

Returns true if this Worker has been told to stop. This could be because of an explicit cancellation signal by the user, or because the system has decided to preempt the task. In these cases, the results of the work will be ignored by WorkManager and it is safe to stop the computation. WorkManager will retry the work at a later time if necessary.

Returns
boolean true if the work operation has been interrupted

onStopped

public void onStopped ()

This method is invoked when this Worker has been told to stop. At this point, the ListenableFuture returned by the instance of startWork() is also cancelled. This could happen due to an explicit cancellation signal by the user, or because the system has decided to preempt the task. In these cases, the results of the work will be ignored by WorkManager. All processing in this method should be lightweight - there are no contractual guarantees about which thread will invoke this call, so this should not be a long-running or blocking operation.

setForegroundAsync

public final ListenableFuture<Void> setForegroundAsync (ForegroundInfo foregroundInfo)

This specifies that the WorkRequest is long-running or otherwise important. In this case, WorkManager provides a signal to the OS that the process should be kept alive if possible while this work is executing.

Calls to setForegroundAsync *must* complete before a ListenableWorker signals completion by returning a ListenableWorker.Result.

Under the hood, WorkManager manages and runs a foreground service on your behalf to execute this WorkRequest, showing the notification provided in ForegroundInfo.

Calling setForegroundAsync will fail with an IllegalStateException when the process is subject to foreground service restrictions. Consider using WorkRequest.Builder.setExpedited(OutOfQuotaPolicy) and getForegroundInfoAsync() instead.

Parameters
foregroundInfo ForegroundInfo: The ForegroundInfo
Returns
ListenableFuture<Void> A ListenableFuture which resolves after the ListenableWorker transitions to running in the context of a foreground Service.

setProgressAsync

public ListenableFuture<Void> setProgressAsync (Data data)

Updates ListenableWorker progress.

Parameters
data Data: The progress Data
Returns
ListenableFuture<Void> A ListenableFuture which resolves after progress is persisted. Cancelling this future is a no-op.

startWork

public abstract ListenableFuture<ListenableWorker.Result> startWork ()

Override this method to start your actual background processing. This method is called on the main thread.

A ListenableWorker has a well defined execution window to to finish its execution and return a ListenableWorker.Result. After this time has expired, the worker will be signalled to stop and its ListenableFuture will be cancelled.

The future will also be cancelled if this worker is stopped for any reason (see onStopped()).

Returns
ListenableFuture<ListenableWorker.Result> A ListenableFuture with the ListenableWorker.Result of the computation. If you cancel this Future, WorkManager will treat this unit of work as failed.