我正在尝试通过移动应用程序通过后端服务器进行身份验证。 我正在关注这个文档。https://developers.google.com/identity/sign-in/android/sign-in https://developers.google.com/identity/sign-in/android/sign-in然而，也存在一些错误。RC_SIGN_IN and updateUI()无法解决。

我的代码是这样的

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {

    ...

       GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
            .requestEmail()
            .build();

       mGoogleSignInClient = GoogleSignIn.getClient(this, gso);

        mSignInButton = findViewById(R.id.sign_in_button);
        mSignInButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Toast.makeText(MainActivity.this, "Hello", Toast.LENGTH_LONG).show();
            Intent signIntent = mGoogleSignInClient.getSignInIntent();
            startActivityForResult(signIntent, RC_SIGN_IN);
        }
    });


   @Override
   protected void onStart() {
        GoogleSignInAccount account = GoogleSignIn.getLastSignedInAccount(this);
        updateUI(account);
        super.onStart();
    }


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

    // Result returned 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);
    }
}


   private void handleSignInResult(Task<GoogleSignInAccount> completedTask) {
       try {
           GoogleSignInAccount account = completedTask.getResult(ApiException.class);
           String idToken = account.getIdToken();

           // Send Id Token to the backend and validate here

           // Signed in successfully, show authenticated UI.
           updateUI(account);
       } catch (ApiException e) {
           // The ApiException status code indicates the detailed failure reason.
           // Please refer to the GoogleSignInStatusCodes class reference for more information.
           Log.w(TAG, "signInResult:failed code=" + e.getStatusCode());
           updateUI(null);
       }
   }

Update

现在按钮本身不起作用。

xml

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">

<!-- Include the main content -->
<FrameLayout
    android:id="@+id/content_frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent">


    <com.google.android.gms.common.SignInButton
        android:id="@+id/sign_in_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/text_view_result"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="#000"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

    </android.support.v4.widget.NestedScrollView>

</FrameLayout>

<!-- Navigation bar -->
<android.support.design.widget.NavigationView
    android:id="@+id/nav_view"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:fitsSystemWindows="true"
    app:menu="@menu/navigation_menu"/>

</android.support.v4.widget.DrawerLayout>

我怎样才能解决这个问题？

您只需更换即可RC_SIGN_IN具有 int 值。它可以是任何值，但不能使用 1 作为其值。执行如下操作：

startActivityForResult(signIntent, 1);

并将活动结果中的 if 代码更改如下：

if (requestCode == 1)

还将登录按钮单击代码更改为此（删除开关盒）：

mSignInButton.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View view) {
                      signIn();
               }
           }
       });

这是因为您正在调用按钮的 click 方法，然后再次检查是否单击了同一个按钮，这就是我认为它不起作用的原因。

现在对于updateUI方法，这个方法应该由你定义。基本上，这是让您的应用程序更改用户登录应用程序时显示的内容。如果您想在以下时间打开新活动signedIn()您可以使用Intent通过改变updateUI(account)在活动结果和 onstart 事件中达到意图：

startActivity(new Intent(MainActivity.this, SecondActivity.class));

并获取登录的是哪个帐户SecondActivity:

GoogleSignInAccount account = GoogleSignIn.g etLastSignedInAccount(this); //use this in onCreate