@Component(modules = MyAppModule.class)
public abstract class MyAppComponent {
 ......
 //使用SubComponent功能来完成component的组合
 abstract ActComponent plus();
}

@Subcomponent(modules = ActModule.class)
public interface ActComponent {
 void inject(ActActivity act);
}

public class MyApplication extends Application {
 @Override
 public void onCreate() {
  super.onCreate();
  MyAppComponent.getInstance().inject(this);
 }
}

  MyAppComponent.getInstance()
    .plus()
    .inject(this);

 //dagger2
 compile 'com.google.dagger:dagger:2.11'
 compile 'com.google.dagger:dagger-android:2.11'
 compile 'com.google.dagger:dagger-android-support:2.11'
 annotationProcessor 'com.google.dagger:dagger-compiler:2.11'
 annotationProcessor 'com.google.dagger:dagger-android-processor:2.11'

@Component(modules = {AndroidInjectionModule.class})
public interface AppComponent {
 //....
}

@Subcomponent(modules = ...)
public interface ActSubComponent extends AndroidInjector<Lychee3Activity> {
 @Subcomponent.Builder
 public abstract class Builder extends AndroidInjector.Builder<Lychee3Activity> {
 }
}

@Module(subcomponents = {ActSubComponent.class})
public abstract class BuildersModule {
 @Binds
 @IntoMap
 @ActivityKey(Lychee3Activity.class)
 abstract AndroidInjector.Factory<? extends Activity> lychee3Activity(ActSubComponent.Builder builder);
 }

@Component(modules = {AndroidInjectionModule.class,
  BuildersModule.class})
public interface AppComponent {
 //....
}

 @ContributesAndroidInjector
 abstract Lychee2Activity lychee2Activity();

public class MyApplication extends Application implements HasActivityInjector {
 @Inject
 DispatchingAndroidInjector<Activity> dispatchingAndroidInjector;

 @Override
 public void onCreate() {
  super.onCreate();
    DaggerAppComponent.builder().AppContent(this).build().inject(this);//最好结合demo来看，不然AppContent是啥你不知道
 }

 @Override
 public AndroidInjector<Activity> activityInjector() {
  return dispatchingAndroidInjector;
 }
}

public class Lychee2Activity extends AppCompatActivity {
 public void onCreate(Bundle savedInstanceState) {
 AndroidInjection.inject(this);
 super.onCreate(savedInstanceState);
 }
}