Flutter iOS使用Firebase_Messaging接受推送通知，给出完整代码

好的，下面是使用Firebase_Messaging接收推送通知的完整Flutter iOS代码：

import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

  final FirebaseMessaging _firebaseMessaging = FirebaseMessaging.instance;

  @override
  void initState() {
    super.initState();
    _firebaseMessaging.requestPermission();
    _firebaseMessaging.configure(
      onMessage: (Map<String, dynamic> message) async {
        print("onMessage: $message");
        showDialog(
          context: context,
          builder: (context) {
            return AlertDialog(
              content: ListTile(
                title: Text(message['notification']['title']),
                subtitle: Text(message['notification']['body']),
              ),
              actions: <Widget>[
                FlatButton(
                  child: Text('Ok'),
                  onPressed: () {
                    Navigator.of(context).pop();
                  },
                ),
              ],
            );
          },
        );
      },
      onResume: (Map<String, dynamic> message) async {
        print("onResume: $message");
      },
      onLaunch: (Map<String, dynamic> message) async {
        print("onLaunch: $message");
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Firebase Messaging',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter Firebase Messaging'),
        ),
        body: Center(
          child: Text('Welcome to Flutter Firebase Messaging'),
        ),
      ),
    );
  }
}

在这个例子中，我们首先使用Firebase.initializeApp()初始化Firebase应用程序，然后创建FirebaseMessaging实例并调用requestPermission()请求权限。接下来，我们使用configure()方法配置FirebaseMessaging以处理不同的消息事件。当应用程序处于前台时，onMessage()方法被调用，我们在这里创建一个AlertDialog来显示推送通知的标题和正文。当应用程序处于后台或未运行时，onResume()和onLaunch()方法被调用，我们可以在这里处理推送通知。

希望这个例子能够帮助你使用Firebase_Messaging接收推送通知。