我正在使用flutter，在Android Studio.
我在控制台中看到以下内容：

W/Firestore(26053): (24.2.2) [OnlineStateTracker]: Could not reach Cloud Firestore backend. Backend didn't respond within 10 seconds
W/Firestore(26053): 
W/Firestore(26053): This typically indicates that your device does not have a healthy Internet connection at the moment. The client will operate in offline mode until it is able to successfully connect to the backend.
E/flutter (26053): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: [cloud_firestore/unavailable] The service is currently unavailable. This is a most likely a transient condition and may be corrected by retrying with a backoff.
E/flutter (26053): #0      checkIfDocExists (package:crypto_app/Functions/firestorehelper.dart:29:5)
E/flutter (26053): <asynchronous suspension>
E/flutter (26053): #1      _MainPagesState._checkUsername (package:crypto_app/UI/mainpages.dart:63:21)
E/flutter (26053): <asynchronous suspension>
E/flutter (26053): 
W/Firestore(26053): (24.2.2) [WatchStream]: (a4a9ed6) Stream closed with status: Status{code=UNAVAILABLE, description=Channel shutdownNow invoked, cause=null}.

我试过：
1.将<uses-permission android:name="android.permission.INTERNET" />放入所有3个AndroidManifest.xml文件中
1.将<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />放在主目录下的AndroidManifest.xml中
1.已启用Multidex
1.使用了不同的wifi连接
1.第二天再次检查，发现问题相同
1.我的最低SDK版本为21
1.将我的代码复制到一个全新的项目
下面是我的主要职能：

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp(
    name: 'Retrospect',
    options: DefaultFirebaseOptions.currentPlatform,
  );

  runApp(MyApp());
}

我应该正确地初始化应用程序，因为我在我的控制台中得到他的：

I/FirebaseApp(26053): Device unlocked: initializing all Firebase APIs for app Retrospect
I/flutter (26053): Refreshing
W/DynamiteModule(26053): Local module descriptor class for com.google.android.gms.providerinstaller.dynamite not found.
I/DynamiteModule(26053): Considering local module com.google.android.gms.providerinstaller.dynamite:0 and remote module com.google.android.gms.providerinstaller.dynamite:0
W/ProviderInstaller(26053): Failed to load providerinstaller module: No acceptable module com.google.android.gms.providerinstaller.dynamite found. Local version is 0 and remote version is 0.

问题可能是由W/DynamiteModule(26053): Local module descriptor class for com.google.android.gms.providerinstaller.dynamite not found.行引起的，我也无法解决。
下面是我的pubspec.yaml文件依赖项：

dependencies:
  flutter:
    sdk: flutter

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^1.0.2
  firebase_core: ^1.20.1
  cloud_firestore: ^3.4.4
  http: ^0.13.4
  path_provider: ^2.0.11
  get_storage: ^2.0.3

我相信我使用的是最新版本的firebase_core和cloud_firestore。
我的app/build.gradle文件依赖项和插件：

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'com.google.gms.google-services'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation "com.android.support:multidex:1.0.3"
    implementation 'com.google.android.material:material:1.6.1'
    implementation 'com.google.android.gms:play-services-ads:21.1.0'
    implementation platform('com.google.firebase:firebase-bom:30.3.2')
    implementation 'com.google.firebase:firebase-analytics-ktx'
    implementation 'com.google.firebase:firebase-storage-ktx'
}

我的build.gradle文件：

buildscript {
    ext.kotlin_version = '1.6.10'
    repositories {
        google()
        mavenCentral()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:7.1.2'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'com.google.gms:google-services:4.3.13'
    }
}

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

google-services.json文件位置：

这里是我在Firestore中的规则（规则不应该是问题，因为我能够使用python成功地读取数据。

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read, write: if
          request.time < timestamp.date(2022, 12, 12);
    }
  }
}

最后，下面是我调用的函数：

import 'package:cloud_firestore/cloud_firestore.dart';

Future<bool> checkIfDocExists(String docId) async {
  try {
    // Get reference to Firestore collection
    var collectionRef = FirebaseFirestore.instance.collection('accounts');

    var doc = await collectionRef.doc(docId).get();
    return doc.exists;
  } catch (e) {
    throw e;
  }
}

是什么导致了这个错误？（我无法通过flutter访问Cloud Firestore）。我没有看到我的防病毒软件（Windows Defender）或防火墙阻止任何东西，但如果需要，我可以提供日志。