Can't print Flutter_downloader progress

Question

I'm trying to use Flutter_downloader to make my app able to download some attachment file and it work just fine. So I make the Isolate into class to tidy things up and tried to use the progress so I can show the download progress in my UI but the progress stays at 0.

How to fix this ? The download work just fine.

Flutter Downloader Isolate Code:

class DownloaderIsolate {
  //Callback for the Flutter_Downloader
  static downloadCallback(String id, DownloadTaskStatus status, int progress) {
    final SendPort send =
        IsolateNameServer.lookupPortByName('downloader_send_port')!;
    send.send([id, status, progress]);
  }

  static setupDownloaderPort({int? progress}) {
    ReceivePort _port = ReceivePort();

    IsolateNameServer.registerPortWithName(
        _port.sendPort, 'downloader_send_port');

    FlutterDownloader.registerCallback(DownloaderIsolate.downloadCallback);

    _port.listen((dynamic data) {
      String id = data[0];
      DownloadTaskStatus status = data[1];
      progress = data[2];
    });
  }
}

My UI Page Code:

int? progress = 0;

void initState(){
    DownloaderIsolate.setupDownloaderPort(progress: progress);
}

Widget build(BuildContext context) {
  //Some Parents Code
  //Trying to show the progress in String
      Text(progress.toString()),
  //Also Trying to show the progress
      Text('$progress'),
}

Answer 1

The problem might be that you need to "setState" in order for your UI to update, but you can't setState in your isolate class. You can try the following:

Flutter Downloader Isolate Code:

static setupDownloaderPort({required Function(int) updateProgress}) {
    ReceivePort _port = ReceivePort();

    IsolateNameServer.registerPortWithName(
        _port.sendPort, 'downloader_send_port');

    FlutterDownloader.registerCallback(DownloaderIsolate.downloadCallback);

    _port.listen((dynamic data) {
      String id = data[0];
      DownloadTaskStatus status = data[1];
      updateProgress(data[2]);
    });
  }

UI Page:

int? progress = 0;

void initState(){
    DownloaderIsolate.setupDownloaderPort(updateProgress: (_p) {
      progress = _p;
    });
    super.initState();
}

Widget build(BuildContext context) {
  //Some Parents Code
  //Trying to show the progress in String
      Text(progress.toString()),
  //Also Trying to show the progress
      Text('$progress'),
}