How to inject WorkManager?

[Monabr]

Hello.

I can't find how to inject WorkManager after searching the documentation.

Could you please tell me how to do this and update the documentation?

[evant]

You'll want to use a https://developer.android.com/reference/androidx/work/WorkerFactory to return your injected instances. Same pattern as what's suggested for fragments in the doc.

[Monabr]

@evant Could you please provide a more detailed explanation of how to do this using the kotlin-inject library? Unfortunately, I couldn't figure it out no matter how hard I tried.

[AdriaBosch]

Hi, I just migrated an Android project from Hilt to kotlin-inject. This is a summary of the code I used to inject WorkManager

@Inject
class MyWorker(
    @Assisted
    private val appContext: Context,
    @Assisted
    private val params: WorkerParameters,
    // Other dependencies
) : CoroutineWorker(appContext, params) {
	
	override suspend fun doWork() {}
}


interface WorkManagerComponent {

    @Provides
    @IntoMap
    fun provideMyWorkerEntry(
        workerCreator: (context: Context, params: WorkerParameters) -> MyWorker,
    ): Pair<KClass<out ListenableWorker>, (Context, WorkerParameters) -> MyWorker> {
        return Pair(MyWorker::class, workerCreator)
    }

   // other workers

    val MyWorkerFactory.provide: WorkerFactory
        @Provides get() = this

    @Singleton
    @Provides
    fun provideWorkManager(context: Context): WorkManager {
        return WorkManager.getInstance(context)
    }
}


@Inject
class MyWorkerFactory(
    private val workersMap: Map<KClass<out ListenableWorker>, (Context, WorkerParameters) -> ListenableWorker>
) : WorkerFactory() {

	override fun createWorker(
	    appContext: Context,
	    workerClassName: String,
	    workerParameters: WorkerParameters
	): ListenableWorker? {
            val entry = workersMap.entries.find {
                Class.forName(workerClassName).isAssignableFrom(it.key.java)
            }
            val workerCreator = entry?.value ?: return null
            return workerCreator(appContext, workerParameters)
	}
}

Then provide WorkerFactory to your application class:

class MyApplication : Application(), Configuration.Provider {

	private lateinit var workerFactory: WorkerFactory

	override fun onCreate() {
		super.onCreate()

		// create your application component

		workerFactory = appComponent.workerFactory
	}

	override fun getWorkManagerConfiguration(): Configuration {
		return Configuration.Builder()
			.setWorkerFactory(workerFactory)
			.build()
	}
}

And don't forget to disable WorkManager initialization from your Manifest.

I hope it helps.

[julius-b]

Thank you so much @AdriaBosch, just a little note though. For me it wouldn't compile until I changed

    @Provides
    @IntoMap
    fun provideMyWorkerEntry(
        workerCreator: (context: Context, params: WorkerParameters) -> MyWorker,
    ): Pair<KClass<out ListenableWorker>, (Context, WorkerParameters) -> MyWorker> {
        return Pair(MyWorker::class, workerCreator)
    }

into

    @Provides
    @IntoMap
    fun provideMyWorkerEntry(
        workerCreator: (context: Context, params: WorkerParameters) -> MyWorker,
    ): Pair<KClass<out ListenableWorker>, (Context, WorkerParameters) -> **ListenableWorker**> {
        return Pair(MyWorker::class, workerCreator)
    }

Even though MyWorker implements ListenableWorker, I had to be the exact same for me to prevent this exception:

[ksp] Cannot find an @Inject constructor or provider for: Map<kotlin.reflect.KClass<out androidx.work.ListenableWorker>, kotlin.Function2<android.content.Context, androidx.work.WorkerParameters, androidx.work.ListenableWorker>>