无法在flutter代码中访问已登录的Google用户？

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

<key>CFBundleURLTypes</key>
<array>
    <dict>
        <key>CFBundleURLSchemes</key>
        <array>
            <string>com.googleusercontent.apps.YOUR_CLIENT_ID</string>
        </array>
    </dict>
</array>
<key>LSApplicationQueriesSchemes</key>
<array>
    <string>google</string>
    <string>googlechrome</string>
    <string>googlechrome-x-callback</string>
</array>

import 'package:google_sign_in/google_sign_in.dart';

void main() {
  GoogleSignIn googleSignIn = GoogleSignIn();
  runApp(MyApp(googleSignIn: googleSignIn));
}

import 'package:google_sign_in/google_sign_in.dart';

class MyLoginPage extends StatelessWidget {
  final GoogleSignIn googleSignIn;

  MyLoginPage({required this.googleSignIn});

  void _handleSignIn() async {
    try {
      await googleSignIn.signIn();
      // 登录成功，可以获取用户信息
    } catch (error) {
      // 登录失败，处理错误信息
    }
  }

  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      onPressed: _handleSignIn,
      child: Text('Google登录'),
    );
  }
}