A: 3 - ui/common/BaseFragment.java

BaseFragment.java

public abstract class BaseFragment extends Fragment implements HasFragmentInjector {

    @Inject
    protected Context activityContext;

    // Note that this should not be used within a child fragment.
    @Inject
    @Named(BaseFragmentModule.CHILD_FRAGMENT_MANAGER)
    protected FragmentManager childFragmentManager;

    @Inject
    DispatchingAndroidInjector<Fragment> childFragmentInjector;

    @SuppressWarnings("deprecation")
    @Override
    public void onAttach(Activity activity) {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
            // Perform injection here for versions before M as onAttach(*Context*) did not yet exist
            // This fixes DaggerFragment issue: https://github.com/google/dagger/issues/777
            AndroidInjection.inject(this);
        }
        super.onAttach(activity);
    }

    @Override
    public void onAttach(Context context) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            // Perform injection here for M (API 23) due to deprecation of onAttach(*Activity*)
            AndroidInjection.inject(this);
        }
        super.onAttach(context);
    }

    @Override
    public final AndroidInjector<Fragment> fragmentInjector() {
        return childFragmentInjector;
    }

    protected final void addChildFragment(@IdRes int containerViewId, Fragment fragment) {
        childFragmentManager.beginTransaction()
                .add(containerViewId, fragment)
                .commit();
    }
}