ApplicationDI.kt

@Singleton
@Component(modules = [
    AndroidInjectionModule::class,
    ApplicationModule::class,
    ActivityModule::class]
)
interface ApplicationComponent {
    @Component.Builder
    interface Builder {
        @BindsInstance
        fun application(application: Application): Builder
        fun build(): ApplicationComponent
    }

    fun inject(app: BaseApplication)
}

@Module
class ApplicationModule {
    @Provides
    @Singleton
    fun providesPetManager(): PetManager {
        return PetManagerImpl()
    }
}

@Module
abstract class ActivityModule {
    @ContributesAndroidInjector(modules = [FragmentBuildersModule::class])
    abstract fun contributesMainActivity(): MainActivity
}

@Module
abstract class FragmentModule {
    @ContributesAndroidInjector
    abstract fun contributesHomeFragment(): HomeFragment
}