java.lang.NullPointerException: Attempt to invoke virtual method ... FirebaseAuth.getCurrentUser()' on a null object reference

Question

I am trying to create a simple journal app but it keeps crashing because of a java null.pointer exception problem. I have been trying to fix it for a while but still could not figure it out. I am using firestore with its authentication feature.

The error is showed at the NewNoteActivity that has the getCurrentUser line.

This is the register activity:

...

public class RegisterActivity extends AppCompatActivity {

    private static final String TAG = "003";
    private EditText emailfield, passfield;
    private FirebaseAuth mAuth;
    private String email, password;

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

        emailfield = (EditText) findViewById(R.id.reg_email);
        passfield = (EditText) findViewById(R.id.reg_password);
        Button submitbtn = (Button) findViewById(R.id.submitRegBtn);

        mAuth = FirebaseAuth.getInstance();

        submitbtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!hasValidationErrors(email, password)) {
                    register();
                }
            }
        });
    }

    private void register() {
        //create user
        mAuth.createUserWithEmailAndPassword(email, password)
                .addOnCompleteListener(RegisterActivity.this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {

                            FirebaseFirestore db = FirebaseFirestore.getInstance();
                            String userId = mAuth.getCurrentUser().getUid();

                            //save username
                            CollectionReference userRef = db.collection("main").document(userId).collection("userinfo");
                            UserInfo userinfo = new UserInfo(email);

                            userRef.add(userinfo).addOnFailureListener(new OnFailureListener() {
                                @Override
                                public void onFailure(@NonNull Exception e) {
                                    Log.e("Failed at userinfo", e.getMessage());
                                }
                            });

                            Intent toMain = new Intent(RegisterActivity.this, NewNoteActivity.class);
                            toMain.putExtra("userinfo", userinfo);
                            startActivity(toMain);
                            Toast.makeText(RegisterActivity.this, "User Created", Toast.LENGTH_SHORT).show();
                        } else {
                            Log.w(TAG, "createUserWithEmail:failure", task.getException());
                            Toast.makeText(RegisterActivity.this, task.getException().getMessage(), Toast.LENGTH_SHORT).show();
                        }
                    }
                });
    }

    @Override
    protected void onStart() {
        super.onStart();
        // Check if user is signed in (non-null) and update UI accordingly.
        FirebaseUser currentUser = mAuth.getCurrentUser();
        if (currentUser != null) {
            Intent toMain = new Intent(RegisterActivity.this, NewNoteActivity.class);
            startActivity(toMain);
        }
    }

    private boolean hasValidationErrors(String emailText, String passText) {
        if (emailText.isEmpty()) {
            emailfield.setError("Required");
            emailfield.requestFocus();
            return true;
        } else if (passText.isEmpty()) {
            passfield.setError("Required");
            passfield.requestFocus();
            return true;
        }
        return false;
    }
}

This is the login activity.

...
public class LoginActivity extends AppCompatActivity {

    private static final String TAG = "002";
    private EditText emailfield, passfield;
    private FirebaseAuth mAuth;
    private String email, password;

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

        emailfield = (EditText) findViewById(R.id.reg_email);
        passfield = (EditText) findViewById(R.id.reg_password);
        Button submitbtn = (Button) findViewById(R.id.submitbtn);

        mAuth = FirebaseAuth.getInstance();

        //get data
        email = emailfield.getText().toString().trim();
        password = passfield.getText().toString().trim();

        submitbtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!hasValidationErrors(email, password)){
                    login();
                }
            }
        });

    }

    private void login() {

        mAuth.signInWithEmailAndPassword(email, password)
                .addOnCompleteListener(LoginActivity.this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {

                        if (task.isSuccessful()){
                            Log.d(TAG, "signInWithEmail:success");
                            FirebaseUser user = mAuth.getCurrentUser();
                            Toast.makeText(LoginActivity.this, "You're logged in :)", Toast.LENGTH_SHORT).show();
                            startActivity(new Intent(LoginActivity.this, NewNoteActivity.class));
                        } else {
                            Log.w(TAG, "signInWithEmail:failure", task.getException());
                            Toast.makeText(LoginActivity.this, Objects.requireNonNull(task.getException()).getMessage(), Toast.LENGTH_SHORT).show();
                        }
                    }
                }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Toast.makeText(LoginActivity.this, "failure listener " + e.getMessage(), Toast.LENGTH_SHORT).show();
            }
        });
    }

    public void toRegisterpage(View view) {
        startActivity(new Intent(LoginActivity.this, RegisterActivity.class));
    }

    @Override
    protected void onStart() {
        super.onStart();
        // Check if user is signed in (non-null) and update UI accordingly.
        FirebaseUser currentUser = mAuth.getCurrentUser();
        if (currentUser!=null){
            Intent toMain = new Intent(LoginActivity.this, NewNoteActivity.class);
            startActivity(toMain);
        }
    }

    private boolean hasValidationErrors(String emailText, String passText) {
        if (emailText.isEmpty()) {
            emailfield.setError("Required");
            emailfield.requestFocus();
            return true;
        } else if (passText.isEmpty()){
            passfield.setError("Required");
            passfield.requestFocus();
            return true;
        }
        return false;
    }
}

add new entry activity

...

public class NewNoteActivity extends AppCompatActivity {

    private RelativeLayout wholeLayout;
    private EditText titleInput, desInput, reflecInput;
    private Toolbar toolbar;

    private FirebaseFirestore db;
    private FirebaseAuth mAuth;
    private String userId;
    private CollectionReference userIdRef;
    private Journal journal;

    private String date, titleText, descText, reflecText;

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

        wholeLayout = (RelativeLayout) findViewById(R.id.wholeLayout);
        titleInput = (EditText) findViewById(R.id.title);
        desInput = (EditText) findViewById(R.id.description);
        reflecInput = (EditText) findViewById(R.id.reflection);

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        Objects.requireNonNull(getSupportActionBar()).setDisplayShowTitleEnabled(false);

        db = FirebaseFirestore.getInstance();
        mAuth = FirebaseAuth.getInstance();

        date = new SimpleDateFormat("EEEE, dd MMM yyyy hh:mm", Locale.getDefault()).format(new Date());

        titleText = titleInput.getText().toString().trim();
        descText = desInput.getText().toString().trim();
        reflecText = reflecInput.getText().toString().trim();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_save:
                saveNote();
                Toast.makeText(this, "Saved!", Toast.LENGTH_SHORT).show();
                break;
            case R.id.action_list:
                Toast.makeText(this, "Loading entries", Toast.LENGTH_SHORT).show();
                break;
            case R.id.action_mail:
                Toast.makeText(this, "Have a suggestion?", Toast.LENGTH_SHORT).show();
                break;
            case R.id.action_settings:
                Toast.makeText(this, "Loading settings", Toast.LENGTH_SHORT).show();
                break;
            default:
                break;
        }
        return true;
    }

    private void saveNote() {
        if (!hasValidationErrors(descText)) {
            if (titleText.isEmpty()) {
                titleText = date;
            } else {
                userId = mAuth.getCurrentUser().getUid();
                userIdRef = db.collection("main").document(userId).collection("journal");
                journal = new Journal(userId, titleText, descText, reflecText, date);

                userIdRef.add(journal).addOnSuccessListener(new OnSuccessListener<DocumentReference>() {
                    @Override
                    public void onSuccess(DocumentReference documentReference) {
                        Toast.makeText(NewNoteActivity.this, "Saved note", Toast.LENGTH_SHORT).show();
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.e("Failed at saving note", e.getMessage());
                        Toast.makeText(NewNoteActivity.this, e.getMessage(), Toast.LENGTH_LONG).show();
                    }
                });
            }
        }
    }

    private boolean hasValidationErrors(String descText) {
        if (descText.isEmpty()) {
            desInput.setError("Required");
            desInput.requestFocus();
            return true;
        }
        return false;
    }
}

error from logcat

08-20 19:11:10.341 6603-6751/com.amethyst.within I/OpenGLRenderer: Initialized EGL, version 1.4
08-20 19:11:10.441 6603-6751/com.amethyst.within D/OpenGLRenderer: Enabling debug mode 0
08-20 19:11:15.601 6603-6603/com.amethyst.within D/AndroidRuntime: Shutting down VM
08-20 19:11:15.601 6603-6603/com.amethyst.within E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.amethyst.within, PID: 6603
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.amethyst.within/com.amethyst.within.NewNoteActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2462)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2534)
        at android.app.ActivityThread.access$900(ActivityThread.java:164)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1419)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:159)
        at android.app.ActivityThread.main(ActivityThread.java:5461)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference
        at com.amethyst.within.NewNoteActivity.onCreate(NewNoteActivity.java:69)
        at android.app.Activity.performCreate(Activity.java:6093)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2415)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2534) 
        at android.app.ActivityThread.access$900(ActivityThread.java:164) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1419) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:159) 
        at android.app.ActivityThread.main(ActivityThread.java:5461) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at java.lang.reflect.Method.invoke(Method.java:372) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759) 
08-20 19:11:15.691 6603-6603/com.amethyst.within I/Process: Sending signal. PID: 6603 SIG: 9
08-20 19:11:15.691 6603-6603/com.amethyst.within V/Process: killProcess [6603] Callers=com.android.internal.os.RuntimeInit$UncaughtHandler.uncaughtException:99 java.lang.ThreadGroup.uncaughtException:693 java.lang.ThreadGroup.uncaughtException:690 <bottom of call stack>

Any help would be very much appreciated.

I guess it's because `mAuth.getCurrentUser()` can return null if there is no user signed in, so your call `mAuth.getCurrentUser().getUid()` is raising an exception, it's better to do a safety check before calling getUid(). — Shermano, Aug 20 '19 at 18:24
@Shermano ideally it should not return null once the user has been created or logged in. — Yash, Aug 20 '19 at 18:24
from [the documentation](https://firebase.google.com/docs/reference/android/com/google/firebase/auth/FirebaseAuth.html#public-firebaseuser-getcurrentuser-): "Use `getCurrentUser() != null` to check if a user is signed in." — Mihir Kekkar, Aug 20 '19 at 18:25
So there can be 2 reasons why user data is not being added, either you've not enabled Firestore in Firebase console or, your user is not being created by Firebase auth, check that the user is created in the register activity by checking the auth entries in firebase console — Yash, Aug 20 '19 at 18:53
There are two places where you are calling `getUid()`. In which one of them are you getting `NullPointerException`? Please responde with @AlexMamo — Alex Mamo, Aug 21 '19 at 07:04
@AlexMamo Thanks! I managed to fix it and it is running well now :) — Lionlollipop, Aug 21 '19 at 17:43
@Lionlollipop Would be nice if you shared how you solved it for future seekers — Itay Feldman, Aug 25 '19 at 09:30

Lionlollipop · Answer 1 · 2019-08-25T16:20:49.423

-3

added this:

  @Override
    protected void onStart() {
        super.onStart();
        // Check if user is signed in (non-null) and update UI accordingly.
        FirebaseUser currentUser = mAuth.getCurrentUser();
        if (currentUser == null) {
            Intent toMain = new Intent(NewNoteActivity.this, RegisterActivity.class);
            startActivity(toMain);
        }
    }

edited Aug 25 '19 at 16:20

answered Aug 25 '19 at 11:58

Lionlollipop

113
3
12

This cannot be the fix for the null pointer log in your question. The error is related to `getCurrentUser()` being null – Giddy Naya Aug 25 '19 at 12:04
1

This cannot possibly solve *any* null pointer problem, and all the `toString()` calls are redundant. – user207421 Aug 25 '19 at 12:05

java.lang.NullPointerException: Attempt to invoke virtual method ... FirebaseAuth.getCurrentUser()' on a null object reference

1 Answers1