// MethodChannel
void XXXPlugin::RegisterWithRegistrar(
	flutter::PluginRegistrarWindows* registrar) {
        // 創(chuàng)建一個(gè)MethodChannel
	auto channel =
		std::make_unique<flutter::MethodChannel<flutter::EncodableValue>>(
			registrar->messenger(), "usb_tool",
			&flutter::StandardMethodCodec::GetInstance());
        // 創(chuàng)建插件對(duì)象
	auto plugin = std::make_unique<XXXPlugin>();
        // 把通道設(shè)置給插件，同時(shí)傳入消息的處理入口
	channel->SetMethodCallHandler(
		[plugin_pointer = plugin.get()](const auto& call, auto result) {
		plugin_pointer->HandleMethodCall(call, std::move(result));
	});
}

// EventChannel
// 創(chuàng)建事件流處理對(duì)象
auto eventHandler = std::make_unique<
StreamHandlerFunctions<EncodableValue>>(
	[plugin_pointer = plugin.get()](
		const EncodableValue* arguments,
		std::unique_ptr<EventSink<EncodableValue>>&& events)
		-> std::unique_ptr<StreamHandlerError<EncodableValue>> {
			return plugin_pointer->OnListen(arguments, std::move(events));
	},
	[plugin_pointer = plugin.get()](const EncodableValue* arguments)
		-> std::unique_ptr<StreamHandlerError<EncodableValue>> {
			return plugin_pointer->OnCancel(arguments);
	});
// 創(chuàng)建EventChannel對(duì)象
auto eventChannel = std::make_unique<flutter::EventChannel<flutter::EncodableValue>>(
	registrar->messenger(), eventChannelName,
	&flutter::StandardMethodCodec::GetInstance());
// 把通道設(shè)置給插件
eventChannel->SetStreamHandler(std::move(eventHandler));

registrar->AddPlugin(std::move(plugin));

// MethodChannel的處理
// result即通信的對(duì)象
void XXXPlugin::HandleMethodCall(
	const flutter::MethodCall<flutter::EncodableValue>& method_call,
	std::unique_ptr<flutter::MethodResult<flutter::EncodableValue>> result) {
        // 匹配通信的接口
	if (method_call.method_name().compare("getPlatformVersion") == 0) {
		std::ostringstream version_stream;
		version_stream << "Windows ";
		if (IsWindows10OrGreater()) {
			version_stream << "10+";
		}
		else if (IsWindows8OrGreater()) {
			version_stream << "8";
		}
		else if (IsWindows7OrGreater()) {
			version_stream << "7";
		}
                // 通過(guò)result->Succes回復(fù)消息
		result->Success(flutter::EncodableValue(version_stream.str()));
	} else {
		result->NotImplemented();
	}
}

// 主動(dòng)向Flutter端發(fā)送消息
std::unique_ptr < flutter::StreamHandlerError<flutter::EncodableValue>> XXXPlugin::OnListen(const flutter::EncodableValue* arguments,
	std::unique_ptr<flutter::EventSink<flutter::EncodableValue>>&& events) {
	// 主動(dòng)發(fā)送
	events_.reset(events.release());
	return nullptr;
}
// Flutter取消監(jiān)聽(tīng)時(shí)觸發(fā)
std::unique_ptr < flutter::StreamHandlerError<flutter::EncodableValue>> UsbToolPlugin::OnCancel(const flutter::EncodableValue* arguments) {
	return nullptr;
}

if (*method == "getAsync") {
            async_pipe_stream_->Get(request, std::bind(&XXXPlugin::OnResponse, this, std::placeholders::_1, *uuid));
            // 直接返回true，但真正的執(zhí)行結(jié)果再OnResponse中主動(dòng)返回
            result->Success(EncodableValue(true)); 
            return;
        }

class NativePlugin {
  static const MethodChannel _channel =
      MethodChannel('com.open.flutter/xxx/xxx');
  static NativePlugin? _instance;
  // 獲取實(shí)例，單例
  static NativePlugin getInstance({String defaultToken = _token}) {
    _instance ??= NativePlugin._internal(defaultToken);
    return _instance!;
  }
  // 私有命名構(gòu)造函數(shù)，做一次初始化
  NativePlugin._internal(String defaultToken) {
    _defaultToken = defaultToken;
    _channel.setMethodCallHandler((MethodCall call) async {
      if (call.method == 'onResponse') {
        final arguments = Map<String, dynamic>.from(call.arguments);
        // 執(zhí)行業(yè)務(wù)端傳入的回調(diào)
        await _onResponse(arguments);
      }
    });
  }