adapter.submitData() not working in Java for android using paging 3

Question

I am using PagingDataAdapter to build my recyclerview but somehow in the mainactivity android studio shows an error that submitData is not a function of the respective adapter.

this is my code for my in the MainActivity:

  viewModel = new ViewModelProvider(this ,
                ViewModelProvider.AndroidViewModelFactory.getInstance(getApplication()))
                .get(PhotoDataSourceFactory.class);
        Lifecycle lifecycle = getLifecycle();
        viewModel.setLifecycle(lifecycle);
        recyclerView = findViewById(R.id.recyclerView);
        PhotosAdapter adapter = new PhotosAdapter(Photos.CALLBACK);
        recyclerView.setAdapter(adapter);
        viewModel.getSearchResults().observe(this, listPagingData -> adapter.submitData(lifecycle, listPagingData));

My ViewModel :

public class PhotoDataSourceFactory extends ViewModel {
    Lifecycle lifecycle;
    private static final String TAG = "PhotoDataSourceFactory";
    public PhotoDataSourceFactory() {
    }

    public void setLifecycle(Lifecycle lifecycle){
        this.lifecycle = lifecycle;
    }

    public LiveData<PagingData<List<Photos>>> getSearchResults(){
        PagingConfig config = new PagingConfig(20, 100, false);
        Pager<Long , List<Photos>> pager = new Pager<>(config, new Function0<PagingSource<Long, List<Photos>>>() {
            @Override
            public PagingSource<Long, List<Photos>> invoke() {
                return new PhotoSource();
            }
        });
        return PagingLiveData.cachedIn(PagingLiveData.getLiveData(pager),lifecycle);
    }


}

My Adapter:

public class PhotosAdapter extends PagingDataAdapter<Photos , PhotosAdapter.PhotoViewHolder> {
    private static final String TAG = "PhotosAdapter";

    public PhotosAdapter(@NotNull DiffUtil.ItemCallback<Photos> diffCallback) {
        super(diffCallback);
    }

    @NonNull
    @Override
    public PhotoViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
        View view = layoutInflater.inflate(R.layout.list_photos,parent,false);
        return new PhotoViewHolder(view);
    }


    @Override
    public void onBindViewHolder(@NonNull PhotoViewHolder holder, int position) {

        Glide.with(holder.itemView.getContext()).load(getItem(position).getUrl()+".png").into(holder.photo);
        holder.textView.setText(getItem(position).getTitle());
    }

    public class PhotoViewHolder extends RecyclerView.ViewHolder{
        ImageView photo;
        TextView textView;
        public PhotoViewHolder(@NonNull View itemView) {
            super(itemView);
            photo = itemView.findViewById(R.id.imageView);
            textView = itemView.findViewById(R.id.textView);
        }

    }
}

and My PagingSource:

public class PhotoSource extends ListenableFuturePagingSource<Long , List<Photos>> {
    GetDataService dataService;
    private static final String TAG = "PhotoSource";
    @NotNull
    @Override
    public ListenableFuture<LoadResult<Long, List<Photos>>> loadFuture(@NotNull LoadParams<Long> loadParams) {
        Executor executor = Executors.newSingleThreadExecutor();
        dataService = RetrofitInstance.getInstance().create(GetDataService.class);
        Long currentPage = loadParams.getKey()!=null ? loadParams.getKey() : (long)1;
        ListenableFuture<List<Photos>> photos =  dataService.getAllPhotos(currentPage);
        ListenableFuture<LoadResult<Long , List<Photos>>> page  = Futures.transform(photos, new Function<List<Photos>, LoadResult<Long, List<Photos>>>() {
            @NullableDecl
            @Override
            public LoadResult.Page<Long, List<Photos>> apply(@NullableDecl List<Photos> input) {
                    return new LoadResult.Page<>(
                            Collections.singletonList(input),
                            currentPage  == 1 ? currentPage : currentPage-1,
                            input.isEmpty() ? null : currentPage+1
                    );
            }}, executor);
        Log.d(TAG, "loadFuture: Heererereree");
        ListenableFuture<LoadResult<Long , List<Photos>>> partialLoad = Futures.catching(page, HttpException.class, LoadResult.Error::new, executor);
        return Futures.catching(partialLoad, IOException.class, LoadResult.Error::new, executor);
    }

    @Nullable
    @Override
    public Long getRefreshKey(@NotNull PagingState<Long, List<Photos>> pagingState) {
        return null;
    }

}

I don't understand where i am going wrong , tried to search alot on stackoverflow but all in vain , I wasn't able to glean anything of substance from google's documentation on paging 3 in java to resolve this issue. tried to find videos on paging 3 in java but unfortunately no one has covered paging in Java.

if there's anyone who has done this (paging 3) in java please if possible add a link to your github too thanks in advance :)

Answer 1

I had encountered a similar issue. In my case, the problem was not with the "adapter.submitData()" but with the actual response itself. The response from the api had issues because of me using suspend function for getting the response data. So, please check the response from your api for debugging.