WorkContinuation

public abstract class WorkContinuation
extends Object

java.lang.Object
   ↳ androidx.work.WorkContinuation


A class that allows you to chain together OneTimeWorkRequests. WorkContinuations allow the user to create arbitrary acyclic graphs of work dependencies. You can add dependent work to a WorkContinuation by invoking then(OneTimeWorkRequest) or its variants. This returns a new WorkContinuation.

To construct more complex graphs, combine(List) or its variants can be used to return a WorkContinuation with the input WorkContinuations as prerequisites. To create a graph like this:

     A       C
     |       |
     B       D
     |       |
     +-------+
         |
         E    
you would write the following:
 WorkContinuation left = workManager.beginWith(A).then(B);
  WorkContinuation right = workManager.beginWith(C).then(D);
  WorkContinuation final = WorkContinuation.combine(Arrays.asList(left, right)).then(E);
  final.enqueue();
Not that enqueuing a WorkContinuation enqueues all previously-unenqueued prerequisites. You must call enqueue() to inform WorkManager to actually enqueue the work graph. As usual, enqueues are asynchronous - you can observe or block on the returned Operation if you need to be informed about its completion.

Because of the fluent nature of this class, its existence should be invisible in most cases.

Summary

Public constructors

WorkContinuation()

Public methods

static WorkContinuation combine(List<WorkContinuation> continuations)

Combines multiple WorkContinuations as prerequisites for a new WorkContinuation to allow for complex chaining.

abstract Operation enqueue()

Enqueues the instance of WorkContinuation on the background thread.

abstract ListenableFuture<List<WorkInfo>> getWorkInfos()

Returns a ListenableFuture of a List of WorkInfos that provides information about the status of each OneTimeWorkRequest in this WorkContinuation, as well as their prerequisites.

abstract LiveData<List<WorkInfo>> getWorkInfosLiveData()

Returns a LiveData list of WorkInfos that provide information about the status of each OneTimeWorkRequest in this WorkContinuation, as well as their prerequisites.

final WorkContinuation then(OneTimeWorkRequest work)

Adds new OneTimeWorkRequest items that depend on the successful completion of all previously added OneTimeWorkRequests.

abstract WorkContinuation then(List<OneTimeWorkRequest> work)

Adds new OneTimeWorkRequest items that depend on the successful completion of all previously added OneTimeWorkRequests.

Inherited methods

Public constructors

WorkContinuation

public WorkContinuation ()

Public methods

combine

public static WorkContinuation combine (List<WorkContinuation> continuations)

Combines multiple WorkContinuations as prerequisites for a new WorkContinuation to allow for complex chaining. For example, to create a graph like this:

     A       C
     |       |
     B       D
     |       |
     +-------+
         |
         E    
you would write the following:
 WorkContinuation left = workManager.beginWith(A).then(B);
  WorkContinuation right = workManager.beginWith(C).then(D);
  WorkContinuation final = WorkContinuation.combine(Arrays.asList(left, right)).then(E);
  final.enqueue();

Parameters
continuations List: One or more WorkContinuations that are prerequisites for the return value

Returns
WorkContinuation A WorkContinuation that allows further chaining

enqueue

public abstract Operation enqueue ()

Enqueues the instance of WorkContinuation on the background thread.

Returns
Operation An Operation that can be used to determine when the enqueue has completed

getWorkInfos

public abstract ListenableFuture<List<WorkInfo>> getWorkInfos ()

Returns a ListenableFuture of a List of WorkInfos that provides information about the status of each OneTimeWorkRequest in this WorkContinuation, as well as their prerequisites.

Returns
ListenableFuture<List<WorkInfo>> A ListenableFuture of a List of WorkInfos

getWorkInfosLiveData

public abstract LiveData<List<WorkInfo>> getWorkInfosLiveData ()

Returns a LiveData list of WorkInfos that provide information about the status of each OneTimeWorkRequest in this WorkContinuation, as well as their prerequisites. If the state or outputs of any of the work changes, any attached Observers will trigger.

Returns
LiveData<List<WorkInfo>> A LiveData containing a list of WorkInfos; you must use LiveData.observe(LifecycleOwner, Observer) to receive updates

then

public final WorkContinuation then (OneTimeWorkRequest work)

Adds new OneTimeWorkRequest items that depend on the successful completion of all previously added OneTimeWorkRequests.

Parameters
work OneTimeWorkRequest: One or more OneTimeWorkRequests to add as dependents

Returns
WorkContinuation A WorkContinuation that allows for further chaining of dependent OneTimeWorkRequests

then

public abstract WorkContinuation then (List<OneTimeWorkRequest> work)

Adds new OneTimeWorkRequest items that depend on the successful completion of all previously added OneTimeWorkRequests.

Parameters
work List: One or more OneTimeWorkRequest to add as dependents

Returns
WorkContinuation A WorkContinuation that allows for further chaining of dependent OneTimeWorkRequests