A: 5 - AppModule.java

AppModule.java

@Module(includes = AndroidInjectionModule.class,
        subcomponents = MainActivitySubcomponent.class)
abstract class AppModule {

    // TODO (ContributesAndroidInjector) remove this in favor of @ContributesAndroidInjector
    @Binds
    @IntoMap
    @ActivityKey(MainActivity.class)
    abstract AndroidInjector.Factory<? extends Activity>
    mainActivityInjectorFactory(MainActivitySubcomponent.Builder builder);
}