RecyclerView Adapter Null Parameter in constructor

Question

may I get an explain as to why one of the parameters i'm passing to my RecyclerViewAdapter is null when I try to access it in the Adapter ? I've been looking at the fragments lifecycle but I cant seem to wrap my head around what's causing it to be null. In onCreateView() I have:

 @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_message, container, false);
        mFirestore = FirebaseFirestore.getInstance();
        String user_id = mAuth.getCurrentUser().getUid();;
        mUsersListView = view.findViewById(R.id.users_list);
        usersList = new ArrayList<>();
        usersRecyclerAdapter = new UsersRecyclerAdapter(container.getContext(), usersList, me);
        mUsersListView.setHasFixedSize(true);
        mUsersListView.setLayoutManager(new LinearLayoutManager(container.getContext()));
        mUsersListView.setAdapter(usersRecyclerAdapter);

        return view;
    }

And in onStart() :

 @Override
    public void onStart() {
        super.onStart();
        usersList.clear();
        mFirestore.collection("Users").addSnapshotListener(getActivity(), (documentSnapshots, e) -> {
            for (DocumentChange documentChange : documentSnapshots.getDocumentChanges()) {
                if (documentChange.getType() == DocumentChange.Type.ADDED) {
                    String user_id = documentChange.getDocument().getId();
                    if (mAuth.getCurrentUser().getUid().matches(user_id)) {
                        me = documentChange.getDocument().toObject(Users.class).withId(user_id);
                        System.out.println(me.getName()); //prints out a name
                        usersRecyclerAdapter.notifyDataSetChanged();
                    } else {
                        Users users = documentChange.getDocument().toObject(Users.class).withId(user_id);
                        usersList.add(users);
                        usersRecyclerAdapter.notifyDataSetChanged();
                    }
                }
            }
        });
    }

My Adapter class looks like this

public class UsersRecyclerAdapter extends RecyclerView.Adapter<UsersRecyclerAdapter.ViewHolder> {
    private List<Users> usersList;
    private Context context;
    private Users me;

    public UsersRecyclerAdapter(Context context, List<Users> usersList, Users me) {
        this.usersList = usersList;
        this.context = context;
        this.me = me;
        System.out.println(me.getName()); //this outputs null
    }

        @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
      //
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {    
        //
    }

}

I want to keep a reference of the me object and pass it on to my adapter. However, when I try to access it there, it triggers a NullPointerException . The List is fine and can be accessed though. How come?

Answer 1

So after discussing in comments, what helped was making a method to update me variable in the adapter:

updateMe(Users me){ this.me = me; }

And calling it from fragment whenever me changes.