platform channels主要用来客户端和宿主app之间消息的传递，异步的形式进行传递
调用过程

1. Flutter客户端发送消息
2. 原生平台接受并返回结果（iOS响应方法:FlutterMethodChannel）(android响应方法:MethodChannel)

具体操作

第一步：Flutter中配置代码触发和接受消息

• MethodChannel配置的参数是唯一的，一般命名规范如下：域名/功能名称
• 使用invokeMethod("方法名称")触发方法

class _TestNativeConnectState extends State<TestNativeConnect> {
  // 命名规则：域名/功能（要唯一 ）
  static const platform1 = const MethodChannel("cy.com/getMessate");
  String _nativeMessate = "null";
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        children: [
          Text("获取原生传递数据:${_nativeMessate}"),
          RaisedButton(
            child: Text("向原生获取数据"),
            onPressed: getDataFromNative,
          )
        ],
      ),
    );
  }
  Future<void> getDataFromNative() async {
    final result = await platform1.invokeMethod("getDataFromNative");//挑起方法
    setState(() {
      _nativeMessate = result;
    });
  }
}

OC代码：

FlutterViewController *controller = (FlutterViewController*)self.window.rootViewController;
FlutterMethodChannel *channel = [FlutterMethodChannel methodChannelWithName:@"cy.come/getMessate" binaryMessenger:controller.binaryMessenger];

__weak typeof(self) weakSelf = self;
[channel setMethodCallHandler:^(FlutterMethodCall *call,FlutterResult result){
    if([@"getDataFromNative" isequalToString:call.method]){
        //result([FlutterError errorWithCode:@"5000",message:"错误信息",details:nil]);
        result(@"iOS - OC");
    }
    else{
        result(FlutterMethodNotImplemented);
    }
}];

第二步：iOS中响应并传递消息

// 获取Flutter ViewController
    let controller : FlutterViewController = window.rootViewController! as! FlutterViewController
    // 创建FlutterMethodChannel
    // 参数一：与flutter中设置的MethodChannel标识对齐  参数二：二进制消息
    let channel = FlutterMethodChannel(name: "cy.com/getMessate", binaryMessenger: controller.binaryMessenger)
    // 监听channel调用方法
    channel.setMethodCallHandler { (call:FlutterMethodCall, result:@escaping FlutterResult) in
        guard call.method == "getDataFromNative" else{//判断方法是否实现
            result(FlutterMethodNotImplemented);//返回当前方法未实现
            return
        }
        // 返回错误信息
//        result(FlutterError(code: "5000", message: "消息不存在", details: nil))
        result("iOS")
    }

第三步：Android中响应并传递消息

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        // 创建methodchannel
        val methodChannel = MethodChannel(flutterEngine.dartExecutor.binaryMessenger,"cy.com/getMessate");
        // 添加回调
        methodChannel.setMethodCallHandler{
            call, result ->
            if (call.method == "getDataFromNative"){
                result.success("android")
                result.error("5000","抛出异常",null)
            }else{
                result.notImplemented()
            }
        }
    }