用於雙向的單次訊息傳遞，包括發送訊息、接收訊息兩個功能

經過以上的實作，其實兩端的通訊步驟都差不多，首先在兩端建立想要Channel並指定名稱，且在兩端通道名稱需對應，傳送端對接收端發訊息來執行Channel的對應的動作（執行Native 端方法，或監聽Native 端訊息，亦或發送訊息至Native 端訊息），接收端建立完對應的Channel後要建立handler處理從傳送端來的訊息執行對應動作，並回傳結果

Flutter 端

新增BasicMessageChannel並指定名稱，且新增要從Flutter 端傳訊息給Native 端的方法，並回傳Native 端要回覆的訊息

lib/batterylevel.dart：

	static const BasicMessageChannel _messageChannel =
      const BasicMessageChannel('chat_message', StringCodec());

  static Future<String> messageResponse(String message) async {
    final String response = await _messageChannel.send(message);
    return response;
  }

Native 端（Android）：

android/.../BatterylevelPlugin.kt：

    private lateinit var messageChannel: BasicMessageChannel<String>

    override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
        //Added
        messageChannel = BasicMessageChannel(
            flutterPluginBinding.binaryMessenger,
            "chat_message",
            StringCodec.INSTANCE
        )
        messageChannel.setMessageHandler { message, reply ->
            val response = if(message.isNullOrEmpty()) "" else "Android 收到：$message"
            reply.reply(response)
        }
    }

    override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
        //Added
        messageChannel.setMessageHandler(null)
    }

Native 端（iOS）：

ios/Classes/RandomNumberStreamHandler.swift

public class SwiftBatterylevelPlugin: NSObject, FlutterPlugin {
    public static func register(with registrar: FlutterPluginRegistrar) {
				//Added
        let messageChannel = FlutterBasicMessageChannel(name: "chat_message", binaryMessenger: 			registrar.messenger(),codec: FlutterStringCodec.sharedInstance())
        
        messageChannel.setMessageHandler {
            (message: Any?, reply: FlutterReply) -> Void in
            reply((message as! String) != "" ? "iOS 收到：\(message as! String)" : "");
        }
    }
}

以上就完成運用Platform Channel來實作平台兩端的通訊了，[範例程式都在這](