如何在Android中使用Dagger 2从应用组件中获取object？

@Module
public class AppModule {
    private final Application application;

    public AppModule(Application application) {
        this.application = application;
    }

    @Provides
    @Singleton
    Application provideApplication() {
        return application;
    }

    @Provides
    @Singleton
    SomeService provideSomeService() {
        return new SomeServiceImpl();
    }
}

@Singleton
@Component(modules = {AppModule.class})
public interface AppComponent {
    void inject(MainActivity mainActivity);
}

public class MyApplication extends Application {
    private AppComponent appComponent;

    @Override
    public void onCreate() {
        super.onCreate();
        appComponent = DaggerAppComponent.builder()
                .appModule(new AppModule(this))
                .build();
    }

    public AppComponent getAppComponent() {
        return appComponent;
    }
}

public class MainActivity extends AppCompatActivity {
    @Inject
    SomeService someService;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ((MyApplication) getApplication()).getAppComponent().inject(this);

        // 现在可以使用 someService 对象了
        someService.doSomething();
    }
}