recyclerview list is not update after search item in SearchView

Question

I'm using RecyclerView and want to implement SearchView with it. I'm working since morning to get this but I'm unable to implement it as I want.

Problem:- When I search any item in RecyclerView then the list is updated correctly after that when I try to search another item then the list goes empty. I want that my list updated automatically on key press from the keyboard. I know there is lot of questions about it on SOF but I tried mostly all of them and I don't understand their code.

All these answers show that We should clear the list object but I cannot figure out how to get back the original list when anybody search any item.

There is my Adapter class:-

public class SongAdapter extends RecyclerView.Adapter<SongViewHolder> implements Filterable{
    private Context context;
    private List<SongObject> allSongs;
    MyEditText options;
    SongViewHolder songViewHolder;
    View view;
    PlaylistCounterDataSource dataSource;
    DataSource fdataSource;
    private List<SongObject> mFilteredList;
    public SongAdapter(Context context, List<SongObject> allSongs) {
        this.context = context;
        this.allSongs = allSongs;
    }
    @Override
    public SongViewHolder onCreateViewHolder(ViewGroup parent, final int viewType) {
        view = LayoutInflater.from(context).inflate(R.layout.song_list_layout, parent, false);

        options = view.findViewById(R.id.options);
        return new SongViewHolder(view);
    }
    @Override
    public void onBindViewHolder(final SongViewHolder holder, final int position) {
        songViewHolder = holder;
        holder.setIsRecyclable(false);

        options.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                showOptions(view, position);
                notifyDataSetChanged();
            }
        });
        SongObject songs = allSongs.get(position);
        holder.songTitle.setText(songs.getSongTitle());
        holder.songAuthor.setText(songs.getSongAuthor());
        Glide.with(context)
                .load(songs.getSongCover())
                .asBitmap()
                .placeholder(R.drawable.default_art)
                .error(R.drawable.default_art)
                .override(200,200)
                .fitCenter()
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .into(holder.songImage);
    }
 @Override
    public int getItemCount() {
        return allSongs.size();
    }

    @Override
    public Filter getFilter() {
        return new Filter() {

            @Override
            protected FilterResults performFiltering(CharSequence charSequence) {
                String charString = charSequence.toString();
                if (charString.isEmpty()) {
                    mFilteredList = allSongs;
                }else {
                    List<SongObject> filteredList = new ArrayList<>();
                    for (SongObject androidVersion : allSongs) {

                        if (androidVersion.getSongTitle().toLowerCase().contains(charString) || androidVersion.getSongAuthor().toLowerCase().contains(charString)) {

                            filteredList.add(androidVersion);

                        }
                    }
                    mFilteredList = filteredList;
                }
                FilterResults filterResults = new FilterResults();
                filterResults.values = mFilteredList;
                Log.d("filter",""+filterResults.values);
                return filterResults;
            }

            @Override
            protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
                allSongs = (ArrayList<SongObject>) filterResults.values;
                notifyDataSetChanged();
            }
        };
    }
}

This is Fragment class :-

 @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        inflater.inflate(R.menu.music_search, menu);
        MenuItem searchItem = menu.findItem(R.id.music_search_bar);
        SearchView searchView = (SearchView) searchItem.getActionView();
        searchView.setQueryHint("Search Song");
        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String s) {
                return false;
            }

            @Override
            public boolean onQueryTextChange(String s) {

                mAdapter.getFilter().filter(s);

            /*   s = s.toLowerCase();
               ArrayList<SongObject> objects = new ArrayList<>();
               for(SongObject so : objects){
                   String name = so.getSongTitle().toLowerCase();
                   if(name.contains(s))
                       objects.add(so);
               }
               mAdapter.filterList(objects);*/

                return true;
            }

        super.onCreateOptionsMenu(menu, inflater);
    }

In some answers they said regenerate recyclerView list when searching string's length is equals to 0. but what happens if there is more item with the same starting letter like:- ABC ADD ADU and it never equals to 0.

Answer 1

     // this is wrong
@Override
    public int getItemCount() {
        return allSongs.size();
    }

// use this 
@Override
    public int getItemCount() {
        return filteredList.size();
    }

in the initial state add all songs to the filteredSongs list then when user query clear the filteredList and add the result to it