A RecyclerView.Adapter extension which adds a callback to assist in the creation of endlessly scrollable lists i.e. lists which load more data as the user reaches the end.

EndlessScrollAdapter.java

public class EndlessScrollAdapter extends RecyclerView.Adapter<EndlessScrollAdapter.ImageViewHolder> {

    private static final String TAG = EndlessScrollAdapter.class.getSimpleName();
  
    private int loadingThreshold = 5; // Default value
    
    private LoadMoreCallback loadMoreCallback;

    public EndlessScrollAdapter() {}

    @Override
    public ImageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        // return viewholder  
    }

    @Override
    public void onBindViewHolder(ImageViewHolder holder, int position) {
        // bind viewholder
        int currentPosition = holder.getAdapterPosition();
        int thresholdDiff = getItemCount() - currentPosition;
        if (loadingThreshold >= thresholdDiff && loadMoreCallback != null) {
            loadMoreCallback.onLoadMore();
        }
    }

    public void setLoadingThreshold(int lastNItems) {
        this.loadingThreshold = lastNItems;
    }

    public void setLoadMoreCallback(LoadMoreCallback loadMoreCallback) {
        this.loadMoreCallback = loadMoreCallback;
    }

    // Implement this to know when to load more data and add it to the adapter
    public interface LoadMoreCallback {

        void onLoadMore();

    }
}