如何在一個 ReceivePort dart 上進行多個訂閱

Question

我的任務是創建 N 個隔離區，以及一個將傳遞給這些隔離區的主 ReceivePort，通過使用這個 ReceivePort，我傳遞了函數所需的所有信息，以便為我提供理想的輸出。 它是第一次工作，但是，向這些隔離區發送的任何連續消息並接收它們都會引發此類錯誤

這是我的代碼

  //main receive port
  var controlPort = ReceivePort();

  ...
  class _MainScreenState extends State<MainScreen> {
  final ImagePicker _picker = ImagePicker();

  Future<ui.Image>? image;

  @override
  void initState() {
    for (int i = 0; i < Platform.numberOfProcessors; i++) {
      Future<Isolate> isolate =
          Isolate.spawn(Core.readAndMapFast, controlPort.sendPort);
    }
  }

  @override
  Widget build(BuildContext context) {

  ...
  static void readAndMapFast(SendPort sendPort) async {
    //sending SendPort of a created isolate to the main thread
    ReceivePort receivePort = ReceivePort();
    sendPort.send(receivePort.sendPort);

    receivePort.first.then((message) {
    //listening for a message coming from main thread and populating it with all needed 
    //data
      message as Arguments;
      Arguments arguments = Arguments(message.imgList, message.lutList,
          message.imgHeight, message.imgWidth, message.widthLut, message.order);
    //ecexuting all needed operations and after that sending message to the main thread
    ...
      sendPort.send(output);

    //in the main thread we are listening for messages from RecievePort we created at 
    //the very beginning

   await for (dynamic message in controlPort.asBroadcastStream()) {
      if (message is SendPort) {

   //waiting for a message from isolates and if its type is SendPort i.e isolate sending 
   //its first message we are sending needed arguments to a function

        message.send(args[i]);
      } else {
        message as FinalList;
        counter++;
        postEditList.add(message);
        if (counter == numberOfWorkers) {
          Stopwatch timerr = Stopwatch();
          timerr.start();
          for (int t = 0; t < postEditList.length; t++) {
            FinalList list =
                postEditList.where((element) => element.order == t).first;
            bytesBuilder.add(list.imgSubList);
          }
          break;
        }
      }
    }

我建議我必須使用 ReceivePort().asBroadcastStream()，但是我不能發送消息並用它做其他事情。 因為當它變成流之后，我們就沒有SendPort了。

Answer 1

我想出了解決辦法。 這很容易。 我們有一個主要的 ReceivePort，我們將使用它來跨隔離區和主線程進行通信，並且我們還創建了一個 BroadcastStream，用於監聽來自我們的 ReceivePort 的任何更新。

var controlPort = ReceivePort();
var broadcastStream = controlPort.asBroadcastStream();

然后你所要做的就是監聽 broadcastStream 而不是 controlPort 的更新

broadcastStream.listen((event) {});

我希望它對那些被困在同一問題上的人有所幫助