showing a progress bar with android paging library

Question

I'm using paging library and room, making my room db as the single layer of truth of my app. when fetching is done from the server using retrofit, i save the result locally in the db then i get the data from the db using paging library. I'm using BoundaryCallback .

@Override
    public void onZeroItemsLoaded() {
        requestAndSaveData();
    }
    @Override
    public void onItemAtEndLoaded(@NonNull Photo itemAtEnd) {
        requestAndSaveData();
}

---

 private void requestAndSaveData() {
        if (isRequestInProgress) return;
        isRequestInProgress = true;
        apiInterface.getPhotos(lastRequestPage, NETWORK_PAGE_SIZE).enqueue(new Callback<PhotoList>() {
            @Override
            public void onResponse(Call<PhotoList> call, Response<PhotoList> response) {
                if (response.isSuccessful()) {
                    cache.insertPhotos(response.body().getHits()); //todo only save 20 - 40 items
                    lastRequestPage++;
                    isRequestInProgress = false;
                    Log.i("deb", "number from boundary: " + response.body().getHits().size());
                }
}

When there is no item in the db or the user scroll to the last item i call requestAndSaveData() method that fetch the data from the server and save it into the db.

My question is how to show a progress bar at the bottom of the list while loading the next page from the server and saving it to the db as it may take a long time?

Answer 1

First of all you could broaden your question scope by asking about how to show a loading indicator in the bottom of RecyclerView instead of narrowing it to the Paging Library..

Secondly, you can easily show a loading indicator in the bottom of your list by adding an extra cell to the list that is just only for showing load indicator, the similar idea is used here to show the network status:

https://github.com/googlesamples/android-architecture-components/blob/master/PagingWithNetworkSample/lib/src/main/java/com/android/example/paging/pagingwithnetwork/reddit/ui/PostsAdapter.kt