解决方案

在FlutterBoost回调中，注册MethodChannel。

val router = INativeRouter { context, url, urlParams, requestCode, exts ->
            val assembleUrl = Utils.assembleUrl(url, urlParams)
            FlutterPageRouter.openPageByUrl(context, assembleUrl, urlParams)
        }

        val boostLifecycleListener = object : FlutterBoost.BoostLifecycleListener {

            override fun beforeCreateEngine() {
                IKLog.i("FlutterComponent beforeCreateEngine")
            }

            override fun onEngineCreated() {
                IKLog.i("FlutterComponent onEngineCreated")
               MethodChannel(FlutterBoost.instance().engineProvider().dartExecutor, "").setMethodCallHandler(...)
            }

            override fun onPluginsRegistered() {
                IKLog.i("FlutterComponent onPluginsRegistered")
            }

            override fun onEngineDestroy() {
                IKLog.i("FlutterComponent onEngineDestroy")
                FlutterPluginManager.release()
            }

        }

        //
        // AndroidManifest.xml 中必须要添加 flutterEmbedding 版本设置
        //
        //   <meta-data android:name="flutterEmbedding"
        //               android:value="2">
        //    </meta-data>
        // GeneratedPluginRegistrant 会自动生成 新的插件方式　
        //
        // 插件注册方式请使用
        // FlutterBoost.instance().engineProvider().getPlugins().add(new FlutterPlugin());
        // GeneratedPluginRegistrant.registerWith()，是在engine 创建后马上执行，放射形式调用
        //

        val platform = FlutterBoost.ConfigBuilder(application, router)
                .isDebug(BuildConfig.DEBUG)
                .whenEngineStart(FlutterBoost.ConfigBuilder.FLUTTER_ACTIVITY_CREATED)
                .renderMode(FlutterView.RenderMode.texture)
                .lifecycleListener(boostLifecycleListener)
                .build()
        FlutterBoost.instance().init(platform)

解决思路

在继承FlutterBoost之前，我们注册MethodChannel通常是采用继承io.flutter.app.FlutterFragmentActivity，然后拿到FlutterView

EventChannel(flutterActivity.flutterView, mName).setStreamHandler(object: EventChannel.StreamHandler{
            override fun onListen(arguments: Any?, events: EventChannel.EventSink?) {
            }

            override fun onCancel(arguments: Any?) {
            }
        })

继承FlutterBoost之后，需要使用boost提供的BoostFlutterActivity，但查看源码并没有FlutterView。

解决这个问题之前，我们先看下MethodChannel的源码。

public MethodChannel(BinaryMessenger messenger, String name) {
        this(messenger, name, StandardMethodCodec.INSTANCE);
    }

看见初始化MethodChannel第一个参数为BinaryMessenger。

BinaryMessenger： 使用与二进制消息一起传递的异步消息与Flutter通信的工具。
我们Flutter提供的FlutterView，其实就是BinaryMessenger

public class FlutterView extends SurfaceView implements BinaryMessenger, TextureRegistry 

拿我们继续看看这个FlutterView实现了BinaryMessenger的方法做了什么。

    public void send(String channel, ByteBuffer message, BinaryReply callback) {
        if (!isAttached()) {
            Log.d(TAG, "FlutterView.send called on a detached view, channel=" + channel);
            return;
        }
        mNativeView.send(channel, message, callback);
    }

继续追mNativeView的源码

    @Override
    @UiThread
    public void send(String channel, ByteBuffer message, BinaryReply callback) {
        if (!isAttached()) {
            Log.d(TAG, "FlutterView.send called on a detached view, channel=" + channel);
            return;
        }

        dartExecutor.getBinaryMessenger().send(channel, message, callback);
    }

由此可见，其实是这个darExecutor在起作用。
再看DartExecutor源码

public class DartExecutor implements BinaryMessenger

是不是恍然大悟，那么只需要从FlutterBoost中拿到DartExecutor即可。

FlutterBoost.instance().engineProvider().dartExecutor

也就是说这个darExecutor已经在FLutterBoost中了，在Engine初始化后就产生了。

IOS解决方案

思路同Android一致

PlatformRouterImp *router = [PlatformRouterImp new];
    [FlutterBoostPlugin.sharedInstance startFlutterWithPlatform:router
                                                        onStart:^(FlutterEngine *engine) {
        [FlutterMethodChannel methodChannelWithName:@"the.bridge" binaryMessenger:engine.binaryMessenger];
                                                        }];