flutter iOS 使用BasicMessageChannel 通信

// main.dart
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final BasicMessageChannel<String> messageChannel =
  BasicMessageChannel<String>('messageChannel', StringCodec());

  String _message = 'No message from iOS';

  @override
  void initState() {
    super.initState();
    messageChannel.setMessageHandler((message) async {
      print("Received message from iOS: $message");
      setState(() {
        _message = 'iOS Response: $message';
      });
      return 'ACK from Dart';
    });
  }

  Future<void> _sendMessageToiOS() async {
    try {
      final String? result = await messageChannel.send('Hello from Flutter!');
      print("Received response from iOS: $result");
    } on PlatformException catch (e) {
      print("Failed to send message to iOS: ${e.message}");
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter - iOS Communication Demo'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              '$_message',
              style: TextStyle(fontSize: 16),
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _sendMessageToiOS,
              child: Text('Send Message to iOS'),
            ),
          ],
        ),
      ),
    );
  }
}

// AppDelegate.swift
import UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
    override func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        let controller = window?.rootViewController as! FlutterViewController
        let messageChannel = FlutterBasicMessageChannel(
            name: "messageChannel",
            binaryMessenger: controller.binaryMessenger,
            codec: FlutterStringCodec.sharedInstance()
        )

        messageChannel.setMessageHandler { [weak self] (message, reply) in
            guard let strongSelf = self else { return }

            print("Received message from Flutter: \(message ?? "")")
            let response = "Hello from iOS! You said: \(message ?? "")"
            reply(response)
        }

        GeneratedPluginRegistrant.register(with: self)
        return super.application(application, didFinishLaunchingWithOptions: launchOptions)
    }
}