Adding items to Endless Scroll RecyclerView with ProgressBar at bottom

The problem is that when you add new item internal EndlessRecyclerOnScrollListener doesn't know about it and counters breaking. As a matter of fact answer with EndlessRecyclerOnScrollListener has some limitations and possible problems, e.g. if you load 1 item at a time it will not work. So here is an enhanced version.

1. Get rid of EndlessRecyclerOnScrollListener we don't need it anymore

2. Change your adapter to this which contains scroll listener

   public class MyAdapter<T> extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
   
       private final int VIEW_ITEM = 1;
       private final int VIEW_PROG = 0;
   
       private List<T> mDataset;
   
       // The minimum amount of items to have below your current scroll position before loading more.
       private int visibleThreshold = 2;
       private int lastVisibleItem, totalItemCount;
       private boolean loading;
       private OnLoadMoreListener onLoadMoreListener;
   
       public MyAdapter(List<T> myDataSet, RecyclerView recyclerView) {
           mDataset = myDataSet;
   
           if (recyclerView.getLayoutManager() instanceof LinearLayoutManager) {
   
               final LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
               recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
                   @Override
                   public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                       super.onScrolled(recyclerView, dx, dy);
   
                       totalItemCount = linearLayoutManager.getItemCount();
                       lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
                       if (!loading && totalItemCount <= (lastVisibleItem + visibleThreshold)) {
                           // End has been reached
                           // Do something
                           if (onLoadMoreListener != null) {
                               onLoadMoreListener.onLoadMore();
                           }
                           loading = true;
                       }
                   }
               });
           }
       }
   
       @Override
       public int getItemViewType(int position) {
           return mDataset.get(position) != null ? VIEW_ITEM : VIEW_PROG;
       }
   
       @Override
       public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
           RecyclerView.ViewHolder vh;
           if (viewType == VIEW_ITEM) {
               View v = LayoutInflater.from(parent.getContext())
                       .inflate(android.R.layout.simple_list_item_1, parent, false);
   
               vh = new TextViewHolder(v);
           } else {
               View v = LayoutInflater.from(parent.getContext())
                       .inflate(R.layout.progress_item, parent, false);
   
               vh = new ProgressViewHolder(v);
           }
           return vh;
       }
   
       @Override
       public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
           if (holder instanceof TextViewHolder) {
               ((TextViewHolder) holder).mTextView.setText(mDataset.get(position).toString());
           } else {
               ((ProgressViewHolder) holder).progressBar.setIndeterminate(true);
           }
       }
   
       public void setLoaded() {
           loading = false;
       }
   
       @Override
       public int getItemCount() {
           return mDataset.size();
       }
   
       public void setOnLoadMoreListener(OnLoadMoreListener onLoadMoreListener) {
           this.onLoadMoreListener = onLoadMoreListener;
       }
   
       public interface OnLoadMoreListener {
           void onLoadMore();
       }
   
       public static class TextViewHolder extends RecyclerView.ViewHolder {
           public TextView mTextView;
   
           public TextViewHolder(View v) {
               super(v);
               mTextView = (TextView) v.findViewById(android.R.id.text1);
           }
       }
   
       public static class ProgressViewHolder extends RecyclerView.ViewHolder {
           public ProgressBar progressBar;
   
           public ProgressViewHolder(View v) {
               super(v);
               progressBar = (ProgressBar) v.findViewById(R.id.progressBar);
           }
       }
   }
   

3. Change code in Activity class

   mAdapter = new MyAdapter<String>(myDataset, mRecyclerView);
   mRecyclerView.setAdapter(mAdapter);
   
   mAdapter.setOnLoadMoreListener(new MyAdapter.OnLoadMoreListener() {
       @Override
       public void onLoadMore() {
           //add progress item
           myDataset.add(null);
           mAdapter.notifyItemInserted(myDataset.size() - 1);
   
           handler.postDelayed(new Runnable() {
               @Override
               public void run() {
                   //remove progress item
                   myDataset.remove(myDataset.size() - 1);
                   mAdapter.notifyItemRemoved(myDataset.size());
                   //add items one by one
                   for (int i = 0; i < 15; i++) {
                       myDataset.add("Item" + (myDataset.size() + 1));
                       mAdapter.notifyItemInserted(myDataset.size());
                   }
                   mAdapter.setLoaded();
                   //or you can add all at once but do not forget to call mAdapter.notifyDataSetChanged();
               }
           }, 2000);
           System.out.println("load");
       }
   });
   

The rest remains unchanged, let me know if this works for you.

I think I figured it out.

I forgot to call notifyItemRangeChanged.

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.add) {
        myDataset.add(0, "Newly added");
        mAdapter.notifyItemInserted(0);
        mAdapter.notifyItemRangeChanged(1, myDataset.size());
        mRecyclerView.smoothScrollToPosition(0);
}
return super.onOptionsItemSelected(item);
}

Once you add it, the code will work, however, you will see that after the spinner finishes spinning, the item number will not increment properly.

This is because the "Newly added" item on top counts as an actual item (we can call it "Item 0"), and this cause the increment to shift by 1 like 21 has been skipped, but actually number 21 has become Item 0. In other words, there are 21 actual items before Item 22.