Binding Activity to the LifecycleOwner with Dagger

Question

I'm creating a lifecycle aware class (that will be injected in the activity). It takes two params - event bus and lifecycle owner. In that case can I bind activity to the lifecycleowner?

My lifecycle aware class:

class Bus @Inject constructor(
        private val eventBus: EventBus,
        private val lifecycleOwner: LifecycleOwner) : LifecycleObserver { ... }

The binding in my module:

@Binds
abstract fun bindLifecycle(activity: SampleActivity): LifecycleOwner

And then I'm injecting the Bus in ActivityX as usual:

@Inject
lateinit var bus: Bus

I'm getting the following error: ActivityX cannot be provided without an @Inject constructor or an @Provides-annotated method.

So my question: is my approach correct OR it's not possible, since activities DON'T support constructor injection?

Answer 1

@Binds annotation "ties" a dependency that is already provided by Dagger to some other type.

By using:

@Inject
lateinit var bus: Bus

you're not making SampleActivity a Dagger dependency (so it is not provided by Dagger ). It only uses dependencies provided by Dagger so it cannot be used with @Binds annotation.

You should have an ActivityModule that can expose a LifecycleOwner as a dependency:

@Module
class ActivityModule(private val activity: AppCompatActivity) {

    @Provides
    fun provideLifecycleOwner(): LifecycleOwner {
        return activity
    }
}

( remember that the class that will use a LifecycleOwner must share the scope with the component that uses ActivityModule )