Dagger 2 “Dagger” prefix component not able to compile? auto generated class

Question

Im trying to use Dagger 2 on android. I previously had it working and i had an appModule injecting dependencies into specific classes in the app. My Issue is that iam getting th

Answer 1

I was having a similar issue with Dagger 2. I had an AppComponent and an ActivityComponent (being a subcomponent). And as soon as I would add a new inject() function in the AppComponent, I would get the above errors.

There was more errors besides the 'cannot find symbol' error but they were very vague and I couldn't debug my issues. After digging and researching stackoverflow and different tutorials, I realized I was using Dagger incorrectly. Specifically the way my AppComponent and ActivityComponent was setup.

I was under the assumption that I could inject my 'Activity' or 'Fragment' with both my AppComponent and ActivityComponent. This turned out to be wrong, at least I found out that it wasn't the right way of using Dagger.

My Solution:

AppComponent

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

    void inject(MyApp application);
    void inject(ContextHelper contextHelper);

    // for exports
    MyApp application();
    PrefsHelper prefsHelper();
}

App Module

@Module
public class AppModule {

    private final MyApp application;

    public AppModule(MyApp application) {

        this.application = application;
    }

    @Provides @Singleton
    public MyApp application() {

        return this.application;
    }

    @Provides @Singleton
    public PrefsHelper providePrefsHelper() {

        PrefsHelper prefsHelper = new PrefsHelper(application);
        return prefsHelper;
    }
}

ActivityComponent

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

    void inject(MainActivity activity);
    void inject(OtherActivity activity);
    void inject(SomeFragment fragment);
}

ActivityModule

@Module
public class ActivityModule {

    private final MyActivity activity;

    public ActivityModule(MyActivity activity) {

        this.activity = activity;
    }

    @Provides @ActivityScope
    public ContextHelper provideContextHelper(MyApp application) {

        // My ContextHelper depends on certain things from AppModule 
        // So I call appComponent.inject(contextHelper)

        AppComponent appComponent = application.getAppComponent();
        ContextHelper contextHelper = new ContextHelper(activity);
        appComponent.inject(contextHelper);
        return contextHelper;
    }
}

Application

public class MyApp extends Application {

    private AppComponent appComponent;

    @Override
    public void onCreate() {

        super.onCreate();
        initializeDepInj();
    }

    private void initializeDepInj() {

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

    public LockAppComponent getAppComponent() {

        return appComponent;
    }
}

Activity

public class MainActivity extends AppCompatActivity {

    // I get it from ActivityModule
    @Inject
    ContextHelper contextHelper;

    // I get it from AppModule
    @Inject
    PrefsHelper prefsHelper;

    ActivityComponent component;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setupInjection();
    }

    protected void setupInjection() {

        MyApp application = (MyApp) getApplication();
        component = DaggerActivityComponent.builder()
                .appComponent(application.getAppComponent())
                .activityModule(new ActivityModule(this))
                .build();
        component.inject(this);

        // I was also doing the following snippet
        // but it's not the correct way since the ActivityComponent depends
        // on AppComponent and therefore ActivityComponent is the only 
        // component that I should inject() with and I'll still get classes
        // that are provided by the AppComponent/AppModule

        // application.getAppComponent().inject(this); // this is unneccessary
    }

    public ContextHelper getContextHelper() {

        return contextHelper;
    }
}

I don't know if it directly resolves your issue but it should at least shed some light on how to use Dagger properly.

Hope it helps.