背景

您好，我是 Firebase for Android 的新手，我第一次尝试实现 Facebook 和 Google 身份验证/登录。我按照这两个教程进行了相应的身份验证:

• http://firebase.google.com/docs/auth/android/google-signin
• http://firebase.google.com/docs/auth/android/facebook-login

另外，FacebookSignInActivity 和 GoogleSignInActivity 正常工作。

问题

问题是我试图在同一 Activity 中使用 Google 和 Facebook 身份验证，但它不起作用。像这样:

我做了什么

我试图让 FacebookSignInActivity 与 GoogleSignInActivity 分开，方法是让它们扩展 MainActivity 并在其中设置布局。

但我认为我应该将两者合而为一。所以我试过了，但我得到了一个奇怪的空指针异常:

java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.firebase.auth.FirebaseAuth.addAuthStateListener(com.google.firebase.auth.FirebaseAuth$AuthStateListener)' on a null object reference

我不知道为什么对象在 onCreate 中为空，因为我从其他两个正在运行的 Activity 中复制了相同的代码:

 mAuth = FirebaseAuth.getInstance();

 mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser user = firebaseAuth.getCurrentUser();
                if (user != null) {
                    // User is signed in
                    Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());
                } else {
                    // User is signed out
                    Log.d(TAG, "onAuthStateChanged:signed_out");
                }
                // [START_EXCLUDE]
                updateUI(user);
                // [END_EXCLUDE]
            }
        };

我什至不确定是否应该将两者合并为一个 Activity 。我还检查了这些链接:

• https://firebase.google.com/docs/auth/android/account-linking
• How to Link Multiple Auth Providers to an Firebase Account?

但看起来这与我正在尝试做的事情不同。如果有人能帮助我指出正确的方向，我将不胜感激。

最佳答案

你可以试试这段代码:

public class LoginActivity extends AppCompatActivity implements GoogleApiClient.OnConnectionFailedListener,
        View.OnClickListener {

    private static final String TAG = "SignInActivity";
    private static final int RC_SIGN_IN = 9001;

    private GoogleApiClient mGoogleApiClient;
    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthListener;

    private CallbackManager mCallbackManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_login);

        // Facebook Login
        FacebookSdk.sdkInitialize(getApplicationContext());
        mCallbackManager = CallbackManager.Factory.create();

        LoginButton mFacebookSignInButton = (LoginButton) findViewById(R.id.facebook_button);
        mFacebookSignInButton.setReadPermissions("email", "public_profile", "user_birthday", "user_friends");

        mFacebookSignInButton.registerCallback(mCallbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                Log.d(TAG, "facebook:onSuccess:" + loginResult);
                firebaseAuthWithFacebook(loginResult.getAccessToken());
            }

            @Override
            public void onCancel() {
                Log.d(TAG, "facebook:onCancel");
            }

            @Override
            public void onError(FacebookException error) {
                Log.d(TAG, "facebook:onError", error);
            }
        });

        // Google Sign-In
        // Assign fields
        Button mGoogleSignInButton = (Button) findViewById(R.id.google_button);

        // Set click listeners
        mGoogleSignInButton.setOnClickListener(this);

        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken(getString(R.string.default_web_client_id))
                .requestEmail()
                .build();
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */)
                .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                .build();

        // Initialize FirebaseAuth
        mAuth = FirebaseAuth.getInstance();

        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser user = firebaseAuth.getCurrentUser();
                if (user != null) {
                    // User is signed in
                    Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());
                } else {
                    // User is signed out
                    Log.d(TAG, "onAuthStateChanged:signed_out");
                }
            }
        };
    }

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

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

    private void firebaseAuthWithGoogle(GoogleSignInAccount acct) {
        Log.d(TAG, "firebaseAuthWithGooogle:" + acct.getId());
        AuthCredential credential = GoogleAuthProvider.getCredential(acct.getIdToken(), null);
        mAuth.signInWithCredential(credential)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        Log.d(TAG, "signInWithCredential:onComplete:" + task.isSuccessful());

                        // If sign in fails, display a message to the user. If sign in succeeds
                        // the auth state listener will be notified and logic to handle the
                        // signed in user can be handled in the listener.
                        if (!task.isSuccessful()) {
                            Log.w(TAG, "signInWithCredential", task.getException());
                            Toast.makeText(LoginActivity.this, "Authentication failed.",
                                    Toast.LENGTH_SHORT).show();
                        } else {
                            startActivity(new Intent(LoginActivity.this, MainActivity.class));
                            finish();
                        }
                    }
                });
    }

    private void firebaseAuthWithFacebook(AccessToken token) {
        Log.d(TAG, "handleFacebookAccessToken:" + token);

        final AuthCredential credential = FacebookAuthProvider.getCredential(token.getToken());
        mAuth.signInWithCredential(credential)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        Log.d(TAG, "signInWithCredential:onComplete:" + task.isSuccessful());

                        // If sign in fails, display a message to the user. If sign in succeeds
                        // the auth state listener will be notified and logic to handle the
                        // signed in user can be handled in the listener.
                        if (!task.isSuccessful()) {
                            Log.w(TAG, "signInWithCredential", task.getException());
                            Toast.makeText(LoginActivity.this, "Authentication failed.",
                                    Toast.LENGTH_SHORT).show();
                        } else {
                            startActivity(new Intent(LoginActivity.this, MainActivity.class));
                            finish();
                        }
                    }
                });
    }

 @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.google_button:
                signIn();
                break;
            default:
                return;
        }
    }

    private void signIn() {
        Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
        startActivityForResult(signInIntent, RC_SIGN_IN);
    }
  @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        mCallbackManager.onActivityResult(requestCode, resultCode, data);

        // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
        if (requestCode == RC_SIGN_IN) {
            GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
            if (result.isSuccess()) {
                // Google Sign In was successful, authenticate with Firebase
                GoogleSignInAccount account = result.getSignInAccount();
                firebaseAuthWithGoogle(account);
            } else {
                // Google Sign In failed
                Log.e(TAG, "Google Sign In failed.");
            }
        }
    }

    @Override
    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
        // An unresolvable error has occurred and Google APIs (including Sign-In) will not
        // be available.
        Log.d(TAG, "onConnectionFailed:" + connectionResult);
        Toast.makeText(this, "Google Play Services error.", Toast.LENGTH_SHORT).show();
    }

}

如果您有任何问题，请告诉我。

关于android - 为 Firebase Android 结合 Facebook 和 Google 身份验证，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/39778301/