CODEWITHSUNDEEP
fileflutterdart
Hoo
Hoo

Reputation: 1840

Flutter .listen called multiple times

I using https://pub.dev/packages/flutter_uploader in my project.

repository

try {
      final result = await InternetAddress.lookup('google.com');
      if (result.isNotEmpty && result[0].rawAddress.isNotEmpty) {
        final taskId = await uploader.enqueue(
            url:
                'https://xxxx',
            files: files,
            data: {
             ....
            },
            method: UploadMethod.POST,
            showNotification: true,
            tag: title);

        final subscription = uploader.result.listen((result) async {
          print("response " + result.response);
        }, onError: (ex, stacktrace) {
          print(ex.toString());
        });
      }
    } catch (e) {
      ...
    }
  }

When first time I call this, uploader.result.listen will only print once. But if I call this method again, uploader.result.listen will call twice. Why?

Edit

I have changed my code to this

PageA

  StreamSubscription<UploadTaskResponse> _subscription;
  FlutterUploader uploader = FlutterUploader();

  @override
  void initState() {
    super.initState();

    _subscription = uploader.result.listen(
      (result) {

         // insert result to database
           .....
      },
      onError: (ex, stacktrace) {
        // ... code to handle error
      },
    );

  }

  void dispose() {
    super.dispose();
    _subscription.cancel();
    _defectBloc.dispose();
  }

In page A, it has floatingActionButton. When the floating action button is clicked, it will open page B. I will pass the uploader param to PageB and bloc, so it can listen to the uploader. Data able to insert into local database if I on the init page. How can I let the insert work too if I exit the app?

Upvotes: 0

Views: 4563

Answers (1)

Midhun MP
Midhun MP

Reputation: 107121

When you call uploader.result.listen it'll add a subscription each time, if you call that n times, n subscription will be added.

To fix the issue, either you need to cancel previous subscription using cancel() method or you have to add the subscription only once (In your initState and cancel in your dispose method).

Upvotes: 2

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