Chaining Work in WorkManager
Introduction
WorkManager is a powerful library in Android for managing deferrable, guaranteed background work. One of its key features is the ability to chain work sequences, where tasks are executed in a specified order. This ensures that one task completes before the next one starts. In this tutorial, we will explore how to chain work using WorkManager.
Setting Up WorkManager
Before we dive into chaining work, let's set up the necessary dependencies for WorkManager in your Android project.
dependencies {
implementation "androidx.work:work-runtime-ktx:2.7.1"
}
Creating Work Requests
To chain work, you first need to create individual WorkRequest objects for each task. Below is an example of creating simple work requests.
class FirstWorker(appContext: Context, workerParams: WorkerParameters) : Worker(appContext, workerParams) {
override fun doWork(): Result {
// Do the work here
return Result.success()
}
}
class SecondWorker(appContext: Context, workerParams: WorkerParameters) : Worker(appContext, workerParams) {
override fun doWork(): Result {
// Do the work here
return Result.success()
}
}
Chaining Work
Once you have your work requests, you can chain them together using the WorkManager. Here's how you can do it:
val firstWorkRequest = OneTimeWorkRequestBuilder<FirstWorker>().build()
val secondWorkRequest = OneTimeWorkRequestBuilder<SecondWorker>().build()
WorkManager.getInstance(applicationContext)
.beginWith(firstWorkRequest)
.then(secondWorkRequest)
.enqueue()
In this example, firstWorkRequest will execute first, and once it completes successfully, secondWorkRequest will start.
Chaining Multiple Work Requests
You can also chain multiple work requests together. Below is an example of chaining three work requests:
val firstWorkRequest = OneTimeWorkRequestBuilder<FirstWorker>().build()
val secondWorkRequest = OneTimeWorkRequestBuilder<SecondWorker>().build()
val thirdWorkRequest = OneTimeWorkRequestBuilder<ThirdWorker>().build()
WorkManager.getInstance(applicationContext)
.beginWith(firstWorkRequest)
.then(secondWorkRequest)
.then(thirdWorkRequest)
.enqueue()
Handling Work Results
When chaining work, it is important to handle the results of each work request. You can pass data between work requests using Data objects. Here's an example:
class FirstWorker(appContext: Context, workerParams: WorkerParameters) : Worker(appContext, workerParams) {
override fun doWork(): Result {
// Do the work here
val outputData = Data.Builder()
.putString("key", "value")
.build()
return Result.success(outputData)
}
}
class SecondWorker(appContext: Context, workerParams: WorkerParameters) : Worker(appContext, workerParams) {
override fun doWork(): Result {
val inputData = inputData
val value = inputData.getString("key")
// Do the work here with the value
return Result.success()
}
}
Combining Parallel Chains
Sometimes you may want to run multiple chains in parallel and wait for all of them to complete before starting another task. WorkManager supports this as well:
val firstWorkRequest = OneTimeWorkRequestBuilder<FirstWorker>().build()
val secondWorkRequest = OneTimeWorkRequestBuilder<SecondWorker>().build()
val thirdWorkRequest = OneTimeWorkRequestBuilder<ThirdWorker>().build()
val fourthWorkRequest = OneTimeWorkRequestBuilder<FourthWorker>().build()
val parallelWorks = mutableListOf<WorkRequest>(firstWorkRequest, secondWorkRequest)
WorkManager.getInstance(applicationContext)
.beginWith(parallelWorks)
.then(thirdWorkRequest)
.then(fourthWorkRequest)
.enqueue()
In this example, firstWorkRequest and secondWorkRequest will run in parallel. Once both complete, thirdWorkRequest and then fourthWorkRequest will run sequentially.
Conclusion
Chaining work in WorkManager allows you to create complex sequences of background tasks that need to be executed in a specific order. This ensures that each task completes successfully before the next one starts, providing a robust solution for handling deferrable background work in Android applications.