Как показывать ProgressBar во время загрузки RecyclerView?

Question

SimpleName @SimpleName

Как показывать ProgressBar во время загрузки RecyclerView?

Есть RecyclerView с картинками, которые загружаются из интернета. Как надо подключить ProgressBar, чтобы он крутился, пока не появится RecyclerView? (ProgressBar не должен показывать точное значение загрузки, а просто крутиться до тех пор,пока не появится RecyclerView с картинками)

адаптер RecyclerView

public class TestAdapter extends RecyclerView.Adapter<TestAdapter.ViewHolder> {

    private TestFragment mContext;
    private ArrayList<GalleryGridObject> galleryArrayList;

    public TestAdapter(TestFragment mContext, ArrayList<GalleryGridObject> galleryArrayList){
        this.mContext=mContext;
        this.galleryArrayList=galleryArrayList;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.item_coupons, parent, false);

        return new ViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        GalleryGridObject gallery = galleryArrayList.get(position);

        Glide.with(mContext).load(gallery.getCompanyImage()).into(holder.imageGallery);
    }

    @Override
    public int getItemCount() {
        if(galleryArrayList==null) return 0;
        return galleryArrayList.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        public ImageView imageGallery;

        public ViewHolder(View view) {
            super(view);
            imageGallery = (ImageView)itemView.findViewById(R.id.coupons_picture);
        }
    }
}

фрагмент

public class TestFragment extends Fragment {

    private ArrayList<GalleryGridObject> galleryList = new ArrayList<GalleryGridObject>();
    private TestAdapter mAdapter;
    private RecyclerView recyclerView;
    ProgressBar progressBar;

    int spanCount = 2; // 2 columns

    public TestFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_coupons, container, false);

        recyclerView = (RecyclerView) view.findViewById(R.id.my_recycler_view);
        progressBar = (ProgressBar) view.findViewById(R.id.progressBar);

        mAdapter = new TestAdapter(this, galleryList);
        LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setAdapter(mAdapter);

        recyclerView.setHasFixedSize(true);

        prepareGalleryData();

        return view;
    }



    private void prepareGalleryData()
    {
        GalleryGridObject gallery = new GalleryGridObject("https://firebasestorage.googleapis.com/v0/b/socialapp-217e6.appspot.com/o/KFC%2F16.jpg?alt=media&token=c2bb063b-3a72-4511-9a09-7679eaea1422");
        galleryList.add(gallery);

        gallery = new GalleryGridObject("https://firebasestorage.googleapis.com/v0/b/socialapp-217e6.appspot.com/o/KFC%2F16.jpg?alt=media&token=c2bb063b-3a72-4511-9a09-7679eaea1422");
        galleryList.add(gallery);

        gallery = new GalleryGridObject("https://firebasestorage.googleapis.com/v0/b/socialapp-217e6.appspot.com/o/KFC%2F16.jpg?alt=media&token=c2bb063b-3a72-4511-9a09-7679eaea1422");
        galleryList.add(gallery);

        gallery = new GalleryGridObject("https://firebasestorage.googleapis.com/v0/b/socialapp-217e6.appspot.com/o/KFC%2F16.jpg?alt=media&token=c2bb063b-3a72-4511-9a09-7679eaea1422");
        galleryList.add(gallery);

        gallery = new GalleryGridObject("https://firebasestorage.googleapis.com/v0/b/socialapp-217e6.appspot.com/o/KFC%2F16.jpg?alt=media&token=c2bb063b-3a72-4511-9a09-7679eaea1422");
        galleryList.add(gallery);

        gallery = new GalleryGridObject("https://firebasestorage.googleapis.com/v0/b/socialapp-217e6.appspot.com/o/KFC%2F16.jpg?alt=media&token=c2bb063b-3a72-4511-9a09-7679eaea1422");
        galleryList.add(gallery);

        gallery = new GalleryGridObject("https://firebasestorage.googleapis.com/v0/b/socialapp-217e6.appspot.com/o/KFC%2F16.jpg?alt=media&token=c2bb063b-3a72-4511-9a09-7679eaea1422");
        galleryList.add(gallery);

        gallery = new GalleryGridObject("https://firebasestorage.googleapis.com/v0/b/socialapp-217e6.appspot.com/o/KFC%2F16.jpg?alt=media&token=c2bb063b-3a72-4511-9a09-7679eaea1422");
        galleryList.add(gallery);

        mAdapter.notifyDataSetChanged();
    }
}