Use Firebase Authenticate UID as child node in Realtime Database

Question

I am trying to add user to the real-time database in Firebase using their auth UID as the child node.

I have been using this question as a guide:

https://stackoverflow.com/questions/40000899/how-to-link-between-authenticated-users-and-database-in-firebase

The users get added when I run the project in debug mode. The app crashes however when I run it normally. The error I am getting is a null pointer exception.

Here is my code:

public class RegisterUser extends AppCompatActivity {

    private static final String TAG = "RegisterUser";

    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthListener;
    private FirebaseUser fbUser =null;
    private DatabaseReference mFirebaseDatabase;
    User user;

    private EditText mEmail, mPassword;
    private RadioButton rManager, rPlayer;
    private Button mRegister;
    private ProgressBar mProgressbar;

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

        mEmail = (EditText) findViewById(R.id.email_field);
        mPassword = (EditText) findViewById(R.id.password_field);
        rManager = (RadioButton) findViewById(R.id.managerBtn);
        rPlayer = (RadioButton) findViewById(R.id.playerBtn);
        mRegister = (Button) findViewById(R.id.btnSignIn);
        mProgressbar = (ProgressBar) findViewById(R.id.progressBar);

        mAuth = FirebaseAuth.getInstance();


        mRegister.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                String email = mEmail.getText().toString();
                String password = mPassword.getText().toString();
                if (TextUtils.isEmpty(email)) {
                    Toast.makeText(getApplicationContext(), "Enter email address!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (TextUtils.isEmpty(password)) {
                    Toast.makeText(getApplicationContext(), "Enter password!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (password.length() < 6) {
                    Toast.makeText(getApplicationContext(), "Password too short, enter minimum 6 characters!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (!rManager.isChecked() && !rPlayer.isChecked()) {
                    Toast.makeText(RegisterUser.this, "You must select either player or manager", Toast.LENGTH_LONG).show();
                }

                mProgressbar.setVisibility(View.VISIBLE);
                String type = "";
                //radio buttons
                if (rManager.isChecked()) {
                    type = "Manager";
                } else if (rPlayer.isChecked()) {
                    type = "Player";
                }
                mFirebaseDatabase = FirebaseDatabase.getInstance().getReference("User");
                String userId = mFirebaseDatabase.push().getKey();
                User user = new User(email, password, type);
                mAuth.createUserWithEmailAndPassword(email, password);
                fbUser = FirebaseAuth.getInstance().getCurrentUser();
                mFirebaseDatabase.child(fbUser.getUid()).setValue(user);
                mProgressbar.setVisibility(View.GONE);
                startActivity(new Intent(RegisterUser.this, HomePage.class));


            @Override
            protected void onResume() {
                super.onResume();
                mProgressbar.setVisibility(View.GONE);
            }

            public void onLogIn(View v) {
                Intent i = new Intent(this, MainActivity.class);
                //i.putExtra(key_1, userName.getText().toString()); //get id for training and display details in full
                startActivity(i);

            }
}

Error:

01-18 17:01:42.331 3781-3781/com.example.cianm.fyp2018v2 E/AndroidRuntime: FATAL EXCEPTION: main
                                                                           Process: com.example.cianm.fyp2018v2, PID: 3781
                                                                           java.lang.NullPointerException
                                                                               at com.example.cianm.fyp2018v2.RegisterUser$1.onClick(RegisterUser.java:142)
                                                                               at android.view.View.performClick(View.java:4463)
                                                                               at android.view.View$PerformClick.run(View.java:18789)
                                                                               at android.os.Handler.handleCallback(Handler.java:808)
                                                                               at android.os.Handler.dispatchMessage(Handler.java:103)
                                                                               at android.os.Looper.loop(Looper.java:193)
                                                                               at android.app.ActivityThread.main(ActivityThread.java:5299)
                                                                               at java.lang.reflect.Method.invokeNative(Native Method)
                                                                               at java.lang.reflect.Method.invoke(Method.java:515)
                                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:829)
                                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:645)
                                                                               at dalvik.system.NativeStart.main(Native Method)

Any help would be greatly appreciated.

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Zoe, Jan 18 '18 at 17:06
What's at RegisterUser line 142, as suggested by your stack trace? — Doug Stevenson, Jan 18 '18 at 17:06
mFirebaseDatabase.child(fbUser.getUid()).setValue(user); @DougStevenson — Cian McGrane, Jan 18 '18 at 17:08
`createUserWithEmailAndPassword()` is an asynchronous operation. You can't call `getCurrentUser()` in the following statement and expect a valid result. — Bob Snyder, Jan 18 '18 at 17:15
@BobSnyder Ok thanks Bob, do you know where to call in then in order to achieve what was done in the linked question? [link](https://stackoverflow.com/questions/40000899/how-to-link-between-authenticated-users-and-database-in-firebase) — Cian McGrane, Jan 18 '18 at 17:23
@CianMcGrane Use AuthStateListener https://firebase.google.com/docs/reference/android/com/google/firebase/auth/FirebaseAuth.AuthStateListener — UdeshUK, Jan 18 '18 at 17:39
@UdeshUk Thank you, using the AuthStateListener did the trick. Posting solution below. — Cian McGrane, Jan 19 '18 at 17:28

score 0 · Accepted Answer · answered Jan 19 '18 at 17:31

By using the onAuthStateChanged I was able to get the current users UID and use it as the child node for the User object.

Code:

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.RadioButton;
import android.widget.Toast;

import com.example.cianm.testauth.Entity.User;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class RegisterUser extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthListener;
    private DatabaseReference mFirebaseDatabase;

    private EditText mEmail, mPassword;
    private Button mRegister;
    private RadioButton rManager, rPlayer;
    private ProgressBar mProgressbar;
    User user;

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

        mEmail = (EditText) findViewById(R.id.emailField);
        mPassword = (EditText) findViewById(R.id.passwordField);
        rManager = (RadioButton) findViewById(R.id.radioManager);
        rPlayer = (RadioButton) findViewById(R.id.radioPlayer);
        mRegister = (Button) findViewById(R.id.registerBtn);
        mProgressbar = (ProgressBar) findViewById(R.id.progressBar);

        mAuth = FirebaseAuth.getInstance();

        if (mAuth.getCurrentUser() != null) {
            startActivity(new Intent(RegisterUser.this, HomePage.class));
        }

        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser fbUser = firebaseAuth.getCurrentUser();
                if (fbUser != null) {
                    // User is signed in
                    Log.d(TAG, "onAuthStateChanged:signed_in" + fbUser.getUid());
                    mFirebaseDatabase = FirebaseDatabase.getInstance().getReference("User");
                    mFirebaseDatabase.child(fbUser.getUid()).setValue(user);
                    Toast.makeText(getApplicationContext(), "Sucessfully signed in with: " + fbUser.getEmail(), Toast.LENGTH_SHORT).show();
                    startActivity(new Intent(RegisterUser.this, HomePage.class));
                } else {
                    // User is signed out
                    Log.d(TAG, "onAuthStateChanged:signed_out");
                }
            }
        };

        mRegister.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String email = mEmail.getText().toString();
                String password = mPassword.getText().toString();
                if (TextUtils.isEmpty(email)) {
                    Toast.makeText(getApplicationContext(), "Enter email address!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (TextUtils.isEmpty(password)) {
                    Toast.makeText(getApplicationContext(), "Enter password!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (password.length() < 6) {
                    Toast.makeText(getApplicationContext(), "Password too short, enter minimum 6 characters!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (!rManager.isChecked() && !rPlayer.isChecked()) {
                    Toast.makeText(RegisterUser.this, "You must select either player or manager", Toast.LENGTH_LONG).show();
                }

                mProgressbar.setVisibility(View.VISIBLE);
                String type = "";
                //radio buttons
                if (rManager.isChecked()) {
                    type = "Manager";
                } else if (rPlayer.isChecked()) {
                    type = "Player";
                }
                mProgressbar.setVisibility(View.VISIBLE);
                mAuth.createUserWithEmailAndPassword(email, password);
                user = new User(email, password, type);
            }
        });
    }

    @Override
    public void onStart() {
        super.onStart();
        mAuth.addAuthStateListener(mAuthListener);
    }

    @Override
    public void onStop() {
        super.onStop();
        if (mAuthListener != null) {
            mAuth.removeAuthStateListener(mAuthListener);
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        mProgressbar.setVisibility(View.GONE);
    }
}

Dwijraj Bhattacharyya · Answer 2 · 2018-01-19T20:57:48.733

After creating user with email and passwoed you need to sign in the user using mAuth.signInWithEmailAndPassword I think your getcurrentuser.getuid() is returning null and thus the null point exception

And also you might wanna

Modify this part-

          mFirebaseDatabase = FirebaseDatabase.getInstance().getReference("User");
            String userId = mFirebaseDatabase.push().getKey();
            User user = new User(email, password, type);
            mAuth.createUserWithEmailAndPassword(email, password);
            fbUser = FirebaseAuth.getInstance().getCurrentUser();
            mFirebaseDatabase.child(fbUser.getUid()).setValue(user);
            mProgressbar.setVisibility(View.GONE);
            startActivity(new Intent(RegisterUser.this, HomePage.class));

as this

         mAuth.createUserWithEmailAndPassword(email,password).addOnSuccessListener(new OnSuccessListener<AuthResult>() {
                    @Override
                    public void onSuccess(AuthResult authResult) {
                         mAuth.signInWithEmailAndPassword(email,password)
                        fbUser =FirebaseAuth.getInstance().getCurrentUser();
                        String userId = fbUser.getUid();       
                        mFirebaseDatabase=       
    FirebaseDatabase.getInstance().getReference("User").child(userId);
            mFirebaseDatabase.child("<Key>").setValue("<Value>"); 
            // Go on adding as many user details you want to

           mProgressbar.setVisibility(View.GONE);
           startActivity(new Intent(RegisterUser.this, HomePage.class));  
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                      // Do something optional
                });

Advantage of this approach- This way while retrieving you can simply Look User Node with Child Uid to get the logged in user's detail (without for looping)

Use Firebase Authenticate UID as child node in Realtime Database

2 Answers2