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android – Adding items to Endless Scroll RecyclerView with ProgressBar at bottom

Posted by: admin April 23, 2020 Leave a comment

Questions:

I followed Vilen’s excellent answer on SO: Put an indeterminate progressbar as footer in a RecyclerView grid on how to implement an endless scroll recyclerview with ProgressBar.

I implemented it myself and it works but I would like to extend the example. I want to add extra items at the top of the recyclerview, similar to how Facebook does it when you add a new status update.

I was not able to add extra items onto the list successfully – here is my code that I added onto Vilen’s code in his MainActivity:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    int id = item.getItemId();

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

When I clicked the “Add” button:

Adding a new item

When I scroll down, I get two spinners instead of one:

Scroll down

When the spinners finish and the next 5 items are loaded, the spinner is still there:

after spinner

What am I doing wrong?

How to&Answers:

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.

Answer:

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.

increment

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.