Attempt to invoke virtual method on a null object reference - Firebase database android

Question

I am trying to read the 'resName' and 'status' values from PjSxhQXCyXdSv07LxVzU7buvhkF2 under business_info node from firebase database, as seen .

I keep getting this error:

Attempt to invoke virtual method 'java.lang.String com.example.android.project_water.Utilities.RestaurantInformation.getResName()' on a null object reference.

Does anyone know how to solve this? Please let me know if more info is needed.

Code:

    public class Info extends Fragment {

        private DatabaseReference mDatabase;
        private FirebaseAuth firebaseAuth;
        private String businessID;
        private TextView resNameChange, statusChange;

        public Info() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {

            View rootView = inflater.inflate(R.layout.fragment_info, container, false);

            SharedPreferences businessID1 = getActivity().getSharedPreferences("BUSINESS_ID", Context.MODE_PRIVATE);
            businessID = businessID1.getString("businessID", "businessIDNotFound");
            Log.i("BUSINESS KEY IS: ", businessID);

            firebaseAuth = FirebaseAuth.getInstance();
            mDatabase = FirebaseDatabase.getInstance().getReference();

            resNameChange = rootView.findViewById(R.id.resNameChange);
            statusChange = rootView.findViewById(R.id.statusChange);

            mDatabase.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    showData(dataSnapshot);
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

            return rootView;
        }

        public void showData(DataSnapshot dataSnapshot) {

            if (dataSnapshot.child("business_info").child(businessID).exists()) {
                for (DataSnapshot ds : dataSnapshot.getChildren()) {
                    RestaurantInformation resInfo = new RestaurantInformation();
//error on the line below******
                    resInfo.setResName(ds.child(businessID).getValue(RestaurantInformation.class).getResName());
                    resInfo.setStatus(ds.child(businessID).getValue(RestaurantInformation.class).getStatus());

                    resNameChange.setText(resInfo.getResName());
                    statusChange.setText(resInfo.getStatus());
                }
            } else {
                resNameChange.setText("NAME");
                statusChange.setText("ONLINE");
            }

        }

    }

My Model

public class RestaurantInformation {

    private String resName;
    private String status;

    public RestaurantInformation() {

    }

    public RestaurantInformation(String resName) {
        this.resName = resName;
    }

    public RestaurantInformation(String resName, String status) {
        this.resName = resName;
        this.status = status;
    }

    public String getResName() {
        return resName;
    }

    public void setResName(String resName) {
        this.resName = resName;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }
}

Answer 1

Your current code is downloading the entire database and then tries to figure out what to show client-side. That is a very wasteful use of your user's bandwidth. I recommend only listening for the business you're interested in:

mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.child("business_info").child(businessID).addValueEventListener(new ValueEventListener() {

Then you can simplify your showData method to:

public void showData(DataSnapshot snapshot) {

    if (snapshot.exists()) {
        RestaurantInformation resInfo = snapshot.getValue(RestaurantInformation.class)

        resNameChange.setText(resInfo.getResName());
        statusChange.setText(resInfo.getStatus());
    } else {
        resNameChange.setText("NAME");
        statusChange.setText("ONLINE");
    }

}