Performing Simple Work

Having a Worker is part of the puzzle. We still need to tell WorkManager to actually use that class to do our work.

If we want to perform the work once — perhaps in response to user input — we can create a OneTimeWorkRequest object to describe that work, then enqueue() it with WorkManager:

OneTimeWorkRequest downloadWork=
  new OneTimeWorkRequest.Builder(DownloadWorker.class)
    .build();

WorkManager.getInstance().enqueue(downloadWork);

We create a OneTimeWorkRequest via its associated Builder, which takes the Java Class object for our Worker subclass its constructor. We build() the Builder and pass the OneTimeWorkRequest to enqueue() on the WorkManager singleton, which we get by calling getInstance() on WorkManager.

After this code executes, at some point in time, an instance of DownloadWorker will be created and doWork() will be called. Exactly when that will be is indeterminate. In this particular case, probably it will be called fairly quickly, with doWork() being executed on a thread in a WorkManager-managed thread pool. However, it is entirely possible that the user leaves our app and our process is terminated before this work can begin. If so, JobScheduler, Firebase JobDispatcher, or AlarmManager will arrange to get that work done later.