Dagger 2.11 - A binding with matching key exists in component

Question

I have a small scenario where I have this following structure where I'm trying to inject fragment manager in baseActivity Fragment but for some reason I'm running out of luck:(

@Singleton
@Component(modules = { AppModule.class,
        ActivityModule.class,
        AndroidSupportInjectionModule.class })
public interface AppComponent extends AndroidInjector<App> {

    @Override
    void inject(App application);

    @Component.Builder interface Builder {

        @BindsInstance
        AppComponent.Builder application(App application);

        AppComponent build();
    }
}

ActivityModule.class

@PerActivity
@ContributesAndroidInjector(modules = BaseActivityModule.class)
abstract BaseActivity baseActivity();

BaseActivityModule.class

static final String ACTIVITY_FRAGMENT_MANAGER = "ACTIVITY_FRAGMENT_MANAGER";

@PerActivity
@Named(ACTIVITY_FRAGMENT_MANAGER)
@Provides
static FragmentManager activityFragmentManager(BaseActivity activity) {
    return activity.getSupportFragmentManager();
}

BaseAcitivity.class

public abstract class BaseActivity extends DaggerAppCompatActivity {

    @Named(ACTIVITY_FRAGMENT_MANAGER)
    @Inject
    FragmentManager fragmentManager;
}

So even though i'm providing my fragment manager in BaseActivityModule.class dagger is throwing this following error. I even tried with just Activity instead of BaseActivity as my input parameter in BaseActivityModule. Even then I land up in this same issue. Not sure what exactly I'm screwing up. So any help is appreciated. Thanks in advance:)

Error:(17, 8) error: [dagger.android.AndroidInjector.inject(T)] @javax.inject.Named("ACTIVITY_FRAGMENT_MANAGER") android.support.v4.app.FragmentManager cannot be provided without an @Provides- or @Produces-annotated method.
@javax.inject.Named("ACTIVITY_FRAGMENT_MANAGER") android.support.v4.app.FragmentManager is injected at
com.abc.views.base.BaseActivity.fragmentManager
com.abc.views.def.ABCActivity is injected at
dagger.android.AndroidInjector.inject(arg0)
A binding with matching key exists in component: om.abc.views.base.BaseActivity_BaseActivity.BaseActivitySubcomponent

Answer 1

"A binding with matching key exists in component" means that you have bound a dependency somewhere in your entire object graph but it cannot be reached from the subcomponent where it needs to be injected. Here is the javadoc :

Utility code that looks for bindings matching a key in all subcomponents in a binding graph so that a user is advised that a binding exists elsewhere when it is not found in the current subgraph. If a binding matching a key exists in a sub- or sibling component, that is often what the user actually wants to use.

For instance, assume you have two Activities, ActivityA and ActivityB . You generate subcomponents with @ContributesAndroidInjector and bind Foo in the ActivityA module but not the ActivityB module. If you request injection for Foo in ActivityB with @Inject Foo foo you will get that error message.

Forming subcomponents using @ContributesAndroidInjector on a base class like BaseActivity is probably not a good approach here. Like in the comment from David Medenjak , the subcomponent for the base class will be ignored and the subcomponent for the concrete class will perform injection on ABCActivity .

For now, you can fix your error by binding FragmentManager in the subcomponent for ABCActivity :

@PerActivity
@ContributesAndroidInjector(modules = BaseActivityModule.class)
abstract ABCActivity ABCActivity();

Answer 2

Did you try provide without static ?

@Module(includes = {ViewModelModule.class})
public class AppModule {

@Provides
public PrefManager providePrefManager(Application app) {
    return PrefManager.getInstance(app);
}