firebase.auth.FirebaseUser.linkWithCredential 抛出空指针异常

Question

How should I link an existing user account with different providers but the same email? For example Google with Facebook.

public void handleFacebookAccessToken(final AccessToken token, final Activity activity) {
        Log.d(TAG, "handleFacebookAccessToken: " + token);

        final AuthCredential credential = FacebookAuthProvider.getCredential(token.getToken());
        mAuth.signInWithCredential(credential)
                .addOnCompleteListener(activity, new OnCompleteListener<AuthResult>() {

                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {
                            // Sign in success, update UI with the signed-in user's information
                            Log.d(TAG, "signInWithCredential:success");
                            FirebaseUser user = mAuth.getCurrentUser();
                            authListener.updateSignedUI(user);
                        }
                    }
                }).addOnFailureListener(activity, new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Log.w(TAG, "signInWithCredential:failure", e);
                if (e instanceof FirebaseAuthUserCollisionException) {
                    handleLinkingFacebookUsers(credential, activity);
                }
            }
        });
    }

In this below method at line with ' mAuth.getCurrentUser().linkWithCredential() NullPointerException occuring.

    private void handleLinkingFacebookUsers(AuthCredential savedFBCredential, Activity activity) {
        //AuthCredential credentialFacebook = FacebookAuthProvider.getCredential(token.getToken());
        //AuthCredential credentialGoogle = GoogleAuthProvider.getCredential(googleIdToken, null);
           mAuth.getCurrentUser()
                   .linkWithCredential(savedFBCredential)   // THIS LINE TROWS NULL POINTER EXCEPTION
                   .addOnCompleteListener(activity, new OnCompleteListener<AuthResult>() {
                       @Override
                       public void onComplete(@NonNull Task<AuthResult> task) {
                           if (task.isSuccessful()) {
                               Log.d(TAG, "linkWithCredential:success");
                               FirebaseUser user = task.getResult().getUser();
                               authListener.updateSignedUI(user);
                           } else {
                               Log.w(TAG, "linkWithCredential:failure", task.getException());
                               authListener.updateSignedUI(null);
                           }

                           // ...
                       }
                   });

    }

Logcat:

com.google.firebase.auth.FirebaseAuthUserCollisionException: An account already exists with the same email address but different sign-in credentials. Sign in using a provider associated with this email address.
        at com.google.firebase.auth.api.internal.zzdv.zza(com.google.firebase:firebase-auth@@19.2.0:42)
        at com.google.firebase.auth.api.internal.zzfc.zza(com.google.firebase:firebase-auth@@19.2.0:19)
        at com.google.firebase.auth.api.internal.zzes.zza(com.google.firebase:firebase-auth@@19.2.0:34)
        at com.google.firebase.auth.api.internal.zzeu.zza(com.google.firebase:firebase-auth@@19.2.0:98)
        at com.google.firebase.auth.api.internal.zzeu.zza(com.google.firebase:firebase-auth@@19.2.0:85)

Any suggestion is appreciated. Thank you.

Answer 1

mAuth.getCurrentUser() is returning a null FirebaseUser because there is no user signed in at the time it was called. Your code should check for this before calling methods on the FirebaseUser object, as showing the API documentation for getCurrentUser() .