Java、Android、Firebase 身份验证登出抛出 NullPointerException

Question

I have an app with email / password firebase authentication.

It starts with the login activity

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

Then in my onStart , I check if the currentuser isn't null, then it navigates to my main activity. This part is working perfectly fine.

@Override
public void onStart() {
    super.onStart();
    FirebaseUser currentUser = mAuth.getCurrentUser();
    if (currentUser != null) {
        goMain();
    }
}

And here comes the problem, in the main activity I have a button where I call the signout function from LoginActivity.java:

public void logOut() {
    LoginActivity login = new LoginActivity();
    login.logMeOut();
}


public void logMeOut() {
    FirebaseUser user = mAuth.getCurrentUser();
    if(user!=null) {
        mAuth.signOut();
        Intent intent = new Intent(this, LoginActivity.class);
        startActivity(intent);
    }
}

Problem is when logMeOut runs, I get this beauty

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

I have tried to add mAuth = FirebaseAuth.getInstance() to the start of the logMeOut function, that still didn't solve my problem.

If I only call mAuth.signOut() , without the FirebaseUser part, I get the same error.

Answer 1

You are creating a new Login activity in your logout method could that be an issue?

It seems to me the Auth objects would be re initialized right there. I do my logout the exact same way as you but it is within the main activity in a menu

 case R.id.sign_out_menu:
            mFirebaseAuth.signOut();
            Auth.GoogleSignInApi.signOut(mGoogleApiClient);