Dagger 2: How to use injection with a Fragment

Sasha Shpota :

I'm using AndroidInjection.inject(this) to inject components into an activity.

AndroidInjection also has an overloaded method that takes android.app.Fragment as a parameter. But my fragments extend android.support.v4.app.Fragment and there is no corresponding method.

Question: How to use injection if a fragment extends android.support.v4.app.Fragment?

dantes_21 :

For support library fragments you need to use support injection. Here some example:

@Singleton
@Component(modules = {
        AndroidSupportInjectionModule.class, // Important
        ActivityModule.class,
        FragmentModule.class
})

public interface AppComponent extends AndroidInjector<App> {

    void inject(App app);

    @Component.Builder
    interface Builder {
        @BindsInstance
        Builder application(Application application);
        AppComponent build();
    }
}

Application, you can use DaggerApplication or simple HasSomeIjection if you need for example Multidex implementation:

public class App extends MultiDexApplication implements
    HasActivityInjector,
    HasFragmentInjector {

    @Inject DispatchingAndroidInjector<Activity> activityInjector;
    @Inject DispatchingAndroidInjector<Fragment> fragmentInjector;
    private AppComponent mComponent;

    @Override
    public void onCreate() {
        mComponent = DaggerAppComponent.builder().application(this).build();
        mComponent.inject(this);
    }

    // Dependency Injection
    @Override
    public DispatchingAndroidInjector<Activity> activityInjector() {
        return activityInjector;
    }

    @Override
    public DispatchingAndroidInjector<Fragment> fragmentInjector() {
        return fragmentInjector;
    }
}

Next module:

@Module
public abstract class FragmentModule {
    @ContributesAndroidInjector
    abstract ContactsFragment bindContactsFragment();
}

Activity module:

@Module
public abstract class ActivityModule {
    @ContributesAndroidInjector
    abstract ContactsActivity bindContactsActivity();
}

And fragment:

import com.some.ContactsPresenter;
import dagger.android.support.DaggerFragment;

public class ContactsFragment extends DaggerFragment {

    @Inject
    ContactsPresenter mContactsPresenter;

    // .....
}

If you don't want use the DaggerFragment, you can open its implementation and copied to your fragment with necessary changes. The main feature here is using AndroidSupportInjectionModule. Hope this will help you