Android Dagger 2 suggest change

Component setup for Application and Activity injection

A basic AppComponent that depends on a single AppModule to provide application-wide singleton objects.

@Singleton
@Component(modules = AppModule.class)
public interface AppComponent {

    void inject(App app);

    Context provideContext();

    Gson provideGson();
}

A module to use together with the AppComponent which will provide its singleton objects, e.g. an instance of Gson to reuse throughout the whole application.

@Module
public class AppModule {

    private final Application mApplication;

    public AppModule(Application application) {
        mApplication = application;
    }

    @Singleton
    @Provides
    Gson provideGson() {
        return new Gson();
    }

    @Singleton
    @Provides
    Context provideContext() {
        return mApplication;
    }
}

A subclassed application to setup dagger and the singleton component.

public class App extends Application {

    @Inject
    AppComponent mAppComponent;

    @Override
    public void onCreate() {
        super.onCreate();

        DaggerAppComponent.builder().appModule(new AppModule(this)).build().inject(this);
    }

    public AppComponent getAppComponent() {
        return mAppComponent;
    }
}

Now an activity scoped component that depends on the AppComponent to gain access to the singleton objects.

@ActivityScope
@Component(dependencies = AppComponent.class, modules = ActivityModule.class)
public interface MainActivityComponent {

    void inject(MainActivity activity);
}

And a reusable ActivityModule that will provide basic dependencies, like a FragmentManager

@Module
public class ActivityModule {

    private final AppCompatActivity mActivity;

    public ActivityModule(AppCompatActivity activity) {
        mActivity = activity;
    }

    @ActivityScope
    public AppCompatActivity provideActivity() {
        return mActivity;
    }
@ActivityScope
public FragmentManager provideFragmentManager(AppCompatActivity activity) {
    return activity.getSupportFragmentManager();
}
}

Putting everything together we’re set up and can inject our activity and be sure to use the same Gson throughout out app!

public class MainActivity extends AppCompatActivity {

    @Inject
    Gson mGson;

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

        DaggerMainActivityComponent.builder()
                .appComponent(((App)getApplication()).getAppComponent())
                .activityModule(new ActivityModule(this))
                .build().inject(this);
    }
}

Feedback about page:

Feedback:
Optional: your email if you want me to get back to you:



Table Of Contents