swift 代码为

//
//  ViewController.swift
//  IOS_to_Flutter
//
//  Created by log on 2021/1/20.
//

import UIKit
import Flutter
 

class ViewController: UIViewController,FlutterStreamHandler {
    
    //初始化的方法
    var channel:FlutterEventChannel?
    var eventSink:FlutterEventSink?
    var flutterViewController:FlutterViewController? = nil
    
    
    //ios 主动给flutter 发送消息回调方法
    func onListen(withArguments arguments: Any?, eventSink events: @escaping FlutterEventSink) -> FlutterError? {
        self.eventSink = events
        return nil
    }
    func onCancel(withArguments arguments: Any?) -> FlutterError? {
        return nil
    }
    
    lazy var flutterEngine:FlutterEngine = FlutterEngine(name: "my flutter engine")
    override func viewDidLoad() {
        super.viewDidLoad()
        //初始化信息
        flutterEngine.run()
        flutterViewController = FlutterViewController(engine: flutterEngine, nibName: nil, bundle: nil)
        self.channel = FlutterEventChannel(name: "com.pages.flutter", binaryMessenger: flutterViewController as! FlutterBinaryMessenger)
        
        self.channel?.setStreamHandler(self)
        // Do any additional setup after loading the view.
    }

    @IBAction func clikc(_ sender: Any) {
        
        //接受flutter 发来的消息
        let  method = FlutterMethodChannel(name: "com.pages.flutter", binaryMessenger: flutterViewController as! FlutterBinaryMessenger)
        method.setMethodCallHandler { (callBack:FlutterMethodCall,  result:FlutterResult) -> Void in
        //获取flutter 返回的信息
            print(callBack.method,callBack.arguments ?? "")
            if callBack.method == "method_native_result_callback" {
                //被动发送消息回传给flutter
                    result("flutter: hello")
            }
        }

        //swift 发送信息给flutter
        let dic:[String:String] = ["hello":"flutter"];
        self.eventSink?(dic)
       
        self.present(flutterViewController!, animated: true, completion: nil)
        
    }
  
    
}

flutter 代码为

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

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

}

class _MyHomePageState extends State<MyHomePage> {
  String _content="234";

  //flutter 发送消息给swift的方法通道
  static const methodChannel = const MethodChannel("com.pages.flutter");
  flutter 接收swift 信息的通道
  static const EventChannel eventChannel = const EventChannel('com.pages.flutter');//App/Event/Channel和iOS的一致
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    //开始监听，swfit 发来的的消息
    eventChannel
        .receiveBroadcastStream("init")
        .listen(_onEvent, onError: _onError);
  }
  // 数据接收
  void _onEvent(Object value) {
    print('fuck me+$value');
    setState(() {
      _content = value.toString();

    });
  }

// 错误处理
  void _onError(dynamic) {}

  @override
  Widget build(BuildContext context) {

    return Scaffold(
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            RaisedButton(
                onPressed: (){
                  //flutter 发送消息的方法
                  methodChannel.invokeMethod("method_no_params",null);
                },
              child: Text('no params'),
            ),
            RaisedButton(
              child: Text('params'),
                onPressed: (){
                  Map<String,String> parms = {"params":"hello swift"};
                  methodChannel.invokeMapMethod("method_params",parms);
                }
            ),
            RaisedButton(
              child: Text("native callback"),
                onPressed: (){
                  _nativeCallBackWithparams();
                }
            ),
            Text(_content != null ? _content : "kong",style: TextStyle(color: Colors.green),)
          ],
        ),
      ),
    );
  }

  Future<Null> _nativeCallBackWithparams() async {
    String result ;
    try{
      result = await methodChannel.invokeMethod("method_native_result_callback",null);
    } on PlatformException catch (e) {
      result = "failed to get params:'${e.message}'";
    }
    setState(() {
      _content = result;
    });
  }


}