Java 无法进行google登录（返回用户为空）

首先，如果这是你见过的最愚蠢的问题，请道歉。但是我在安卓谷歌登录方面遇到了麻烦。我正在申请谷歌登录

public class MainActivity extends AppCompatActivity {

private static final int RC_SIGN_IN = 1;
private GoogleSignInClient mGoogleSignInClient;

private FirebaseAuth mAuth;
SignInButton signInButton;

@Override
protected void onStart() {
    super.onStart();

    isUserSignedIn();
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    //Result return from launching the Intent from GoogleSignInClient.getSignInIntent(...);
    if (requestCode == RC_SIGN_IN) {
        // The Task returned from this call is always completed
        // no need to attach a listener
        Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
        handleSignInResult(task);
    } else
        Log.d("activity", "not done");
}

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);



}

private void isUserSignedIn() {
    GoogleSignInAccount account = GoogleSignIn.getLastSignedInAccount(this);

    if (account == null) {
        promptSignIn();
    } else updateUI(account);
}

private void promptSignIn() {
    // Configure sign-in to request the user's ID, email address, and basic profile
    // ID and basic profile are included in DEFAULT_SIGN_IN
    GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
            .requestIdToken(getString(R.string.default_web_client_id))
            .requestEmail()
            .build();

    // Build a GoogleSignInClient with the options specified by gso
    mGoogleSignInClient = GoogleSignIn.getClient(this, gso);

    // Set the dimensions of the sign-in button
    signInButton = findViewById(R.id.google_btn);
    signInButton.setSize(SignInButton.SIZE_STANDARD);
    signInButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            signIn();
        }
    });
}

private void signIn() {
    Intent signInIntent = mGoogleSignInClient.getSignInIntent();
    startActivityForResult(signInIntent, RC_SIGN_IN);
}

private void handleSignInResult(Task<GoogleSignInAccount> completedTask) {
    try {
        GoogleSignInAccount account = completedTask.getResult();

        // Signed in successfully, show authenticated UI
        updateUI(account);

    } catch (Exception e) {
        Log.d("activity", "signInResult:failed code=" + e.getMessage());
    }


    FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
    if (user != null) {
        // Name, email address, and profile photo Url
        String name = user.getDisplayName();
        String email = user.getEmail();
        Uri photoUrl = user.getPhotoUrl();

        // Check if user's email is verified
        boolean emailVerified = user.isEmailVerified();

        Log.d("activity", name);
        Log.d("activity", email);
        Log.d("activity", photoUrl + "");
        Log.d("activity", emailVerified + "");

        // The user's ID, unique to the Firebase project. Do NOT use this value to
        // authenticate with your backend server if you have one. Use
        // FirebaseUser.getToken() instead.
        String uid = user.getUid();
    } else
        Log.d("activity", "user is null");
}

protected void updateUI(GoogleSignInAccount account) {
    if (signInButton != null) signInButton.setVisibility(View.GONE);
}}  

应用程序级别>>>

构建脚本{

repositories {
    google()
    jcenter()
}
dependencies {
    classpath 'com.android.tools.build:gradle:3.0.1'
    classpath 'com.google.gms:google-services:3.1.1'

    // NOTE: Do not place your application dependencies here; they belong
    // in the individual module build.gradle files }}allprojects {
    repositories {
        google()
        jcenter()
    }
}
task clean(type: Delete) {
    delete rootProject.buildDir
}

---

该用户为空，因为您从未通过Firebase登录该用户。使用Google登录Firebase时，您需要通过两个API登录该用户

添加以下方法

private void firebaseAuthWithGoogle(GoogleSignInAccount acct) {
    Log.d(TAG, "firebaseAuthWithGoogle:" + 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) {
                if (task.isSuccessful()) {
                    // Sign in success
                    FirebaseUser user = mAuth.getCurrentUser();
                } else {
                    // Sign in failed
                }
            }
        });

private void firebaseAuthWithGoogle（谷歌签名帐户）{
Log.d（标记为“firebaseAuthWithGoogle:+acct.getId（））；
AuthCredential credential=GoogleAuthProvider.getCredential（acct.getIdToken（），null）；
mAuth.SIGNWITH凭证（凭证）
.addOnCompleteListener（这是新的OnCompleteListener（）{
@凌驾
未完成的公共void（@NonNull任务）{
if（task.issusccessful（））{
//成功登录
FirebaseUser=mAuth.getCurrentUser（）；
}否则{
//登录失败
}
}
});

}

添加私有FirebaseAuth mAuth；

将

mAuth=FirebaseAuth.getInstance（）；

添加到onCreate（）中

在handleSignInResult（）中，当Google登录成功时，调用firebaseAuthWithGoogle（）

---

在我的例子中，我得到了与“空用户”相同的错误

但是，我犯的愚蠢错误是

我忘记初始化私有FirebaseAuth mAuth；

一旦我初始化了如下的变量，问题就解决了。。。 mAuth=FirebaseAuth.getInstance（）；

---

注意：添加mAuth=FirebaseAuth.getInstance（）；到onCreate（）

但它给了我“signInResult:failed code=尝试在空对象引用上调用虚拟方法'com.google.android.gms.tasks.com.google.firebase.auth.FirebaseAuth.signInWithCredential（com.google.firebase.auth.AuthCredential）'”我更新了我的答案，如果不清楚，您需要的详细信息缺失。您在Firebase项目中启用了登录方法吗？是的，谢谢您的合作。我想Marcus给了我答案。您有什么建议吗？

private void firebaseAuthWithGoogle(GoogleSignInAccount acct) {
    Log.d(TAG, "firebaseAuthWithGoogle:" + 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) {
                if (task.isSuccessful()) {
                    // Sign in success
                    FirebaseUser user = mAuth.getCurrentUser();
                } else {
                    // Sign in failed
                }
            }
        });