I am trying to implement a UI in a fragment, where user can make all sorts of updates and I need send it over to backend when user EXITS the screen. (Batch update)
I am using MVVM pattern, where network calls are performed from viewmodel . Now, viewModelScope.launch won't work here, since as soon as user exits, the coroutine is canceled by onCleared().
For now, I added GlobalScope and it works but I have also come across this and this question
Are there any other alternatives to accomplish this with Coroutines?
Coroutines are mostly recommended for work that should start immediately and is scoped to the lifecycle of a Fragment, Activity, ViewModel or any other object with a lifecycle. Since the rest of the coroutine builders are tied to scopes, they wont accomplish what you are trying to do, since the user might leave your app at any given time.
A better approach would be using WorkManager with CoroutineWorker, which isn't tied to your UIs or App lifespan and still takes the advantages of working with Coroutines. With WorkManager, your work could be enqueued when the user leaves your designated screen and will be guaranteed to run once the constraints you specify are fulfilled (for example having internet connection). I recommend you to check Android's Guide to background processing if you are still making up your mind on which solution to use.
To use WorkManager you have to subclass one of the available Worker classes:
ListenableWorker
Worker
RxWorker
CoroutineWorker
I want to run the job every 2 hours. Some of the answers mentioned should be use Listenable Worker. I am confusing this which one suits to this scenario. Please help me on this.
WorkManager has some extensive documentation on how to use it that also includes a migration guide covering the move from Firebase JobDispatcher.
In the documentation you can find a section that explain the different threading behaviour of the different Worker classes.
In your particular case, it really depends if what you want to execute periodically is synchronous or not.
If what you want to run is synchronous: use a Worker
If what you want to run asynchround: use a CoroutineWorker if you're using Kotlin, otherwise you've to use a ListenableWorker.
Which is fastest Kotlin Coroutines or Work Manager API to fetch images and videos from an Android phone. Or any other Methods ?
Coroutines are designed to provide a lightweight asynchronous programming framework. You can use Coroutines to start async job which is bounded to the local lifecycle scope of some part of your app. For example, if you want to call a REST API when the user clicks the "login" button. In this case, you don't really care if this result was complete (for example the user can go back and the task will cancel). If you need to be sure the task will complete then the WorkManager would be a better choice (e.g. it would be suitable for a long-running upload task which would be better to perform in the background).
If you'd like to see more about the practical use of coroutines for async jobs on Android I can recommend my article:
https://www.netguru.com/codestories/android-coroutines-%EF%B8%8Fin-2020
I wonder why should I bother with rx or coroutines when there is brilliant solution as WorkManager. But for almost all tutorials they use coroutines so may be WorkManager has disadvantages ?
The scope of both is different. WorkManager is to schedule deferrable (for any later time) or immediately.
tasks asynchronously.
As documentation says
The WorkManager API makes it easy to specify deferrable, asynchronous
tasks and when they should run. These APIs let you create a task and
hand it off to WorkManager to run immediately or at an appropriate
time.
On the other hand, coroutines are designed to compute a given task only immediately and asynchronously.
Also
Internally, coroutines and WorkManager work differently. Work manager heavily depends on Android system components like Services, Alarm manager, etc to schedule the work whereas coroutines schedule the work on Worker Threads and also is a language feature unlike WorkManager (API). So it is safe to say that coroutines do not go beyond your application. On the other hand, WorkManager can even execute the given tasks when your application is not active. for instance, background services.
Also as Marko answered, using coroutines will lead to better code readability and quality due to their fundamental design.
I would also like to include ANKO, Its a great library that provides a helpful API around coroutines for Android.
Background tasks fall into one of the following main categories:
Immediate
Deferred
Exact
To categorize a task, answer the following questions:
Does the task need to complete while the user is interacting with the application?
If so, this task should be categorized for immediate execution. If
not, proceed to the second question.
Does the task need to run at an exact time?
If you do need to run a task at an exact time, categorize the task as
exact.
Most tasks don't need to be run at an exact time. Tasks generally allow for slight variations in when they run that are based on conditions such as network availability and remaining battery. Tasks that don't need to be run at an exact time should be categorized as deferred.
Use Kotlin Coroutine when a task needs to execute immediately and if the task will end when the user leaves a certain scope or finishes an interaction.
Use WorkManager when a task needs to execute immediately and need continued processing, even if the user puts the application in the background or the device restarts
Use AlarmManager when a task that needs to be executed at an exact point in time
For more details, visit this link
If your goal is writing clean code without explicitly constructed callbacks you pass to background tasks, then you'll find that coroutines are the only option.
Using coroutines by no means precludes using WorkManager or any other tool for background operations of your choosing. You can adapt the coroutines to any API that provides callbacks as a means to continue the execution with the results of background operations.
From official Documentation:
It is important to note that coroutines is a concurrency framework, whereas WorkManager is a library for persistent work.
WorkManager:
Support for both asynchronous one-off and periodic tasks
Support for constraints such as network conditions, storage space, and charging status
Chaining of complex work requests, including running work in parallel
Output from one work request used as input for the next
Handles API level compatibility back to API level 14(see note)
Works with or without Google Play services
Follows system health best practices
LiveData support to easily display work request state in UI
Waits proper time to run.
Coroutines:
Clean code, works under the hood in a different way. Run immediately.
So depending on your requirements choose the better option.
Has others replied, WorkManager solves a different problem than Kotlin's corountines or a reactive library like RxJava.
WorkManager is now available as beta and additional documentation is produced that hopefully makes this clear.
One of these documents is the blog post I worte with some colleagues: Introducing WorkManager, where you can read:
A common confusion about WorkManager is that it’s for tasks that needs to be run in a “background” thread but don’t need to survive process death. This is not the case. There are other solutions for this use case like Kotlin’s coroutines, ThreadPools, or libraries like RxJava. You can find more information about this use case in the guide to background processing.
I've used JobScheduler for a while now. A typical example would be:
JobScheduler triggers the onStartJob() method. This kicks off some sort of task that might include several other background processes (getting device position, making a network call, etc). I then use an interface to call back to the JobService once the task is complete or if it fails.
However, with WorkManager it seems like there is basically no way to run work asynchronously. I know WorkManager will run Workers in a separate thread but it seems like a single worker must run synchronously? If so I'll have to rework a lot of the logic in my app it seems unless I'm missing something.
Say I had a weather app and it would use the JobScheduler to run a JobService that did the following:
onStartJob() --> get device position --> make API request for local weather data -> write to database -> call jobFinished()
With WorkManager, is the intended implementation of something like this to chain multiple workers together? And if so, how do you pass data from one Worker to another? Again, seems like it would be a massive undertaking for any slightly complex app to migrate to the WorkManager API.
I think what you are looking for is a ListenableWorker. It has exactly that interface. Rather than you having to call jobFinished() in the end, we do the work for you when you resolve the ListenableFuture.
https://developer.android.com/reference/androidx/work/ListenableWorker.html#startWork() is analogous to onStartJob in your case.