本文章分为两部分，第一部分是flutter向原生端传参，第二部分是原生向Flutter传参。
flutter向原生传参我们将调用原生的Toast来显示所传的参数。原生向Flutter传参我们将原生所传参数显示在Flutter页面中。
一、Flutter向原生端传参
首先我们先看Flutter端的代码：

InkWell(
              child: Text('show native data'),
              onTap:()=>sendData('this is flutter send to show native'),
            )

这里的sendData里面的参数就是向原生端传递的。
在看看sendData里面的实现：

void sendData(String result) {
    FlutterPlugins.senData(result);
  }

class FlutterPlugins{

  static const MethodChannel channel = const MethodChannel("hyflapp");

  static Future<void> senData(String result) async{
    await channel.invokeMethod('sendData',result);
  }
}

MethodChannel里面的参数是需要和原生端保持一致的，可以使用包名或者约定一个。
此时Flutter端的代码已经实现完成了，我们在看看原生端的:
打开Flutter项目中的android项目，在MainActivity中添加，

val CHANNEL:String = "hyflapp"
lateinit var methodChannel:MethodChannel
override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        methodChannel =       
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger,CHANNEL)
        GeneratedPluginRegistrant.registerWith(flutterEngine)
        methodChannel.setMethodCallHandler { call, result ->
            if (call.method.equals("sendData")) {
                Toast.makeText(context, call.arguments.toString(), Toast.LENGTH_SHORT).show()
            }
        }
    }

这里的CHANNEL值需要与Flutter中保持一致。MainActivity需要继承FlutterActivity,否则没有configureFlutterEngine方法。
此时运行代码点击对应的Text控件，将会在屏幕弹出Toast。
如果你的Flutter项目是一个flutter module依赖到一个Android原生项目的，此时我们需要新建一个FlutterPlugins，代码如下:

class FlutterPluginsChannel(activity: Activity) : FlutterPlugin,MethodChannel.MethodCallHandler {

    lateinit var channel:MethodChannel
    private val context:Context = activity


    fun registerWith(flutterEngine: FlutterEngine){
        flutterEngine.plugins.add(this)
    }

    override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
        channel = MethodChannel(binding.binaryMessenger,context.packageName)
        channel.setMethodCallHandler(this)
    }

    override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
        channel.setMethodCallHandler(null)
    }

    override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
        if(call.method.equals("sendData")){
            Toast.makeText(context,call.arguments.toString(),Toast.LENGTH_SHORT).show()
        }
    }
}

然后我们在承载Flutter内容的页面中添加：

flutterEngine = FlutterEngine(this)
flutterEngine.dartExecutor.executeDartEntrypoint(
            DartExecutor.DartEntrypoint.createDefault()
        )
FlutterPluginsChannel(this).registerWith(flutterEngine)

二、原生向Fluterr传输数据
同上面的例子我们在原生的plugins的onMethodCall中添加：

if (call.method == "sendToFlutter) {
      result.success("this data is send to flutter")
    }

然后我们打开Flutter项目中的FlutterPlugins文件：

static Future<String?> get sendToFlutter async {
    final String? datas = await _channel.invokeMethod('sendToFlutter');
    return datas;
  }

然后在显示页面添加：

String _datas = 'Unknown';
Future<void> initPlatformState() async {
    String datas;
    try {
      datas =
          await FlutterPlugins.datas ?? 'Unknown';
    } on PlatformException {
      datas = 'Failed to get platform version.';
    }
    if (!mounted) return;
    setState(() {
      _datas = datas;
    });
  }