Firebase Database Reference Error: No such instance field: 'mDatabaseReference'

Question

I'm using Firebase Realtime Database to store data for a project. I'm using Android Studio and Java to create a mobile app. In this particular activity, a new user is filling out a form to sign up for the service. Once they input their info and hit the submit button, the on click handles that info and inserts it into the Database.

Here is the relevant code for that class:

public class CreateUserActivity extends AppCompatActivity {
private DatabaseReference mDatabaseReference;

private List<String> mInterestList;

private EditText mUsername;
private EditText mPassword;
private EditText mEmail;
private EditText mLocation;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_create_user);

    mDatabaseReference = FirebaseDatabase.getInstance().getReference();

    mInterestList = new ArrayList<>();

    mUsername = findViewById(R.id.text_username);
    mPassword = findViewById(R.id.text_password);
    mEmail = findViewById(R.id.text_email);
    mLocation = findViewById(R.id.text_location);
}

public void onCheckboxClicked(View view) {
    CheckBox checkbox = (CheckBox) view;
    boolean isChecked = checkbox.isChecked();
    String interest = checkbox.getText().toString();

    if(isChecked) {
        mInterestList.add(interest);
    }else {
        mInterestList.remove(interest);
    }
}

public void onSaveUser(View view) {
    String username = mUsername.getText().toString();
    String password = mPassword.getText().toString();
    String email = mEmail.getText().toString();
    String location = mLocation.getText().toString();

    if(TextUtils.isEmpty(username) ||
        TextUtils.isEmpty(password) ||
        TextUtils.isEmpty(email) ||
        TextUtils.isEmpty(location) ||
        mInterestList.size() == 0) {
        displayToast("Please enter values for all fields");
    }else {
        List<String> interests = mInterestList;
        User user = new User(username, password, email, location, interests, null);

        mDatabaseReference.child("users").child(username).setValue(user, new DatabaseReference.CompletionListener() {
            @Override
            public void onComplete(@Nullable DatabaseError databaseError, @NonNull DatabaseReference databaseReference) {
                if(databaseError != null) {
                    Log.e(GetTogetherApp.LOG_TAG, databaseError.getMessage());
                }else{
                    displayToast("User created!");
                }
            }
        });
    }
}

As I've run through breakpoints the error seems to fire on this line:

mDatabaseReference.child("users").child(username).setValue()

Specifically once I try and enter into the setValue() method. The other two child() calls work to find the path as intended. I have the database reference set as a member variable, so I'm not sure why it seems to lose it at that point.

Here's a look at my database structure

Firebase Database Structure Pic

Error in Android Studio:

Answer 1

The error message in your screenshot is in the variable inspector in the Android Studio debugger. It means that where the error occurs, there is no variable mDatabaseReference so the debugger can't show its value. This is not the actual cause of the crash, merely the debugger telling you that it can't show you something you asked for.

You can find the actual cause of the problem by inspecting the InvocationTargetException e.