检索Firebase令牌时出现问题: 7，Flutter - SafetyNet Phone_Auth

dependencies:
  firebase_core: ^2.10.3
  firebase_auth: ^3.3.1
  google_sign_in: ^5.0.7
  flutter_safetynet: ^2.0.0

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

import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter_safetynet/flutter_safetynet.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Firebase Auth Example')),
        body: PhoneAuthScreen(),
      ),
    );
  }
}

class PhoneAuthScreen extends StatefulWidget {
  @override
  _PhoneAuthScreenState createState() => _PhoneAuthScreenState();
}

class _PhoneAuthScreenState extends State<PhoneAuthScreen> {
  final TextEditingController _controller = TextEditingController();
  final FirebaseAuth _auth = FirebaseAuth.instance;

  Future<void> _signInWithPhone(String phoneNumber) async {
    await _auth.verifyPhoneNumber(
      phoneNumber: phoneNumber,
      verificationCompleted: (PhoneAuthCredential credential) async {
        await _auth.signInWithCredential(credential);
      },
      verificationFailed: (FirebaseAuthException e) {
        print(e.message);
      },
      codeSent: (String verificationId, int? resendToken) {
        // Handle code sent
      },
      codeAutoRetrievalTimeout: (String verificationId) {
        // Handle timeout
      },
    );
  }

  Future<void> _verifySafetyNet() async {
    try {
      final SafetyNetResponse response = await FlutterSafetynet.verify();
      print(response.json);
    } catch (e) {
      print(e);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        TextField(
          controller: _controller,
          decoration: InputDecoration(labelText: 'Phone Number'),
        ),
        ElevatedButton(
          onPressed: () {
            _signInWithPhone(_controller.text);
          },
          child: Text('Sign In with Phone'),
        ),
        ElevatedButton(
          onPressed: _verifySafetyNet,
          child: Text('Verify SafetyNet'),
        ),
      ],
    );
  }
}