要在Flutter中使用Firebase进行登录，并且支持Apple登录，你可以按照以下步骤进行操作：

1. 添加依赖项： 在Flutter项目的pubspec.yaml文件中，添加以下依赖项：

dependencies:
  firebase_core: ^0.4.0+9
  firebase_auth: ^0.14.0+5
  google_sign_in: ^4.0.7
  apple_sign_in: ^0.1.0

运行flutter pub get以获取依赖项。

2. 配置Firebase项目： 在Firebase控制台创建一个新的项目，并将Android和iOS应用添加到该项目中。在Android应用中，下载并添加google-services.json文件。在iOS应用中，下载并添加GoogleService-Info.plist文件。

3. 配置Android项目： 在Android项目的android/build.gradle文件中，添加以下代码：

dependencies {
    // ...
    classpath 'com.google.gms:google-services:4.2.0'
}

在Android项目的android/app/build.gradle文件的底部添加以下代码：

apply plugin: 'com.google.gms.google-services'

4. 配置iOS项目： 在iOS项目的ios/Podfile文件中添加以下代码：

pod 'Firebase/Auth'

然后运行以下命令来安装依赖项：

cd ios
pod install

5. 配置Flutter代码： 在Flutter项目的lib/main.dart文件中，添加以下代码示例：

import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';
import 'package:apple_sign_in/apple_sign_in.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Firebase Login',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: LoginPage(),
    );
  }
}

class LoginPage extends StatelessWidget {
  final FirebaseAuth _auth = FirebaseAuth.instance;
  final GoogleSignIn _googleSignIn = GoogleSignIn();

  Future signInWithGoogle() async {
    final GoogleSignInAccount googleUser = await _googleSignIn.signIn();
    final GoogleSignInAuthentication googleAuth = await googleUser.authentication;

    final AuthCredential credential = GoogleAuthProvider.credential(
      accessToken: googleAuth.accessToken,
      idToken: googleAuth.idToken,
    );

    final UserCredential userCredential = await _auth.signInWithCredential(credential);
    return userCredential;
  }

  Future signInWithApple() async {
    final AuthorizationResult result = await AppleSignIn.performRequests([
      AppleIdRequest(requestedScopes: [Scope.email, Scope.fullName])
    ]);

    switch (result.status) {
      case AuthorizationStatus.authorized:
        final AuthCredential credential = OAuthProvider('apple.com').credential(
          idToken: String.fromCharCodes(result.credential.identityToken),
          accessToken: String.fromCharCodes(result.credential.authorizationCode),
        );

        final UserCredential userCredential = await _auth.signInWithCredential(credential);
        return userCredential;
      case AuthorizationStatus.error:
        throw FirebaseAuthException(
          code: 'apple_sign_in_failed',
          message: result.error.toString(),
        );
      case AuthorizationStatus.cancelled:
        throw FirebaseAuthException(
          code: 'apple_sign_in_cancelled',
          message: 'Sign in with Apple has been cancelled by the user.',
        );
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Firebase Login'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            RaisedButton(
              onPressed: () async {
                try {
                  final UserCredential userCredential = await signInWithGoogle();
                  print('User signed in with Google: ${userCredential.user.displayName}');
                } catch (e) {
                  print('Failed to sign in with Google: $e');
                }
              },
              child: Text('Sign in with Google'),
            ),
            RaisedButton(
              onPressed: () async {
                try {
                  final UserCredential userCredential = await signInWithApple();
                  print('User signed in with Apple: ${userCredential.user.displayName}');
                } catch (e) {
                  print('Failed to sign in with Apple: $e');
                }
              },
              child: Text('Sign in with Apple'),