Android 中的 Dagger 2 和组件依赖

Question

Activity

@PerActivity
@Component(modules = [ActivityModule::class])
interface ActivityComponent

Application

@Singleton
@Component(modules = [
    HttpModule::class,
    ApplicationModule::class
])
interface AppComponent

Activity Specific

@Component(
        modules = [LandingModule::class],
        dependencies = [AppComponent::class, ActivityComponent::class]
)
@ActivityContext
interface LandingComponent {
    fun inject(activity: MainActivity)
}

Apply

   override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        DaggerLandingComponent.builder().build().inject(this)
   }

The error I'm getting is that AppComponent has a singleton scope cannot depend on scoped components:

What's the proper solution in this case?

Answer 1

One common way to address this is to add a plus method to your parent component. So ActivityComponent is technically AppComponent + ActivityComponent and LandingComponent is AppComponent + ActivityComponent + LandingComponent .

@Singleton
@Component(modules = [
    HttpModule::class,
    ApplicationModule::class
])
interface AppComponent {
    ActivityComponent plus(module: ActivityModule)
}

@PerActivity
@Subcomponent(modules = [ActivityModule::class])
interface ActivityComponent {
    LandingComponent plus(module: LandingModule)
}

@ActivityContext
@Subcomponent(modules = [LandingModule::class])
interface LandingComponent {
    fun inject(activity: MainActivity)
}

Apply

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    AppComponent.builder().build().plus(ActivityModule()).plus(LandingModule())
}