public class UserViewModel extends ViewModel {

    public LiveData<PagedList<User>> userList;

    public UserViewModel() {

    }

    public void init(UserDao userDao) {
        PagedList.Config pagedListConfig =
                (new PagedList.Config.Builder()).setEnablePlaceholders(true)
                        .setPrefetchDistance(10)
                        .setPageSize(20).build();

        userList = (new LivePagedListBuilder(userDao.usersByFirstName(),
                pagedListConfig))
                .build();

    }
}

public class UserAdapter extends PagedListAdapter<User, UserAdapter.UserItemViewHolder> {


    protected UserAdapter() {
        super(User.DIFF_CALLBACK);
    }

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

    @Override
    public void onBindViewHolder(UserItemViewHolder holder, int position) {
        User user= getItem(position);
        if(user!=null) {
            holder.bindTo(user);
        }
    }

    static class UserItemViewHolder extends RecyclerView.ViewHolder {
        TextView userName, userId;

        public UserItemViewHolder(View itemView) {
            super(itemView);
            userId = itemView.findViewById(R.id.userId);
            userName = itemView.findViewById(R.id.userName);
        }

        public void bindTo(User user) {
            userName.setText(user.firstName);
            userId.setText(String.valueOf(user.userId));
        }
    }
}

UserViewModel viewModel =
                ViewModelProviders
                        .of(this)
                        .get(UserViewModel.class);
        viewModel.init(userDao);
        final UserAdapter userUserAdapter = new UserAdapter();

        viewModel.userList.observe(this, pagedList -> {
            Toast.makeText(this, "Page " + pagedList.size(), Toast.LENGTH_SHORT).show();
            Log.e("Paging ", "Page " + pagedList.size());
            userUserAdapter.setList(pagedList);
        });

        recyclerView.setAdapter(userUserAdapter);