ScrollUpdateNotification setState cause scrollview jump to the last index

[ldhlfzysys]

The popular pull_to_refresh plugin has a problem, the author says it may cause by flutter. there is demo video and example

peng8350/flutter_pulltorefresh#430
peng8350/flutter_pulltorefresh#523

[darshankawar]

@ldhlfzysys
Please provide flutter doctor -v, a complete minimal reproducible code sample that we can directly use that shows the issue you are reporting along with actual vs expected behavior.

Thanks.

[ldhlfzysys]

@darshankawar beta branch and stable branch can reproduction this error

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[darshankawar]

a complete minimal reproducible code sample that we can directly use that shows the issue you are reporting along with actual vs expected behavior.

@ldhlfzysys
As requested above, please provide complete code sample that we can directly run to verify the issue along with actual vs expected behavior.

[ldhlfzysys]

@darshankawar
Do not release touch. scrollview will jump to last index of datas.

void main() => runApp(Test());

class Test extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _TestState();
  }
}

class _TestState extends State<Test> {
  List data = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
  bool _loading = false;
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            appBar: AppBar(title: Text('test')),
            body: NotificationListener(
                child: ListView.separated(
                  padding: EdgeInsets.only(left: 5, right: 5),
                  itemBuilder: (c, i) => Card(
                    child: Container(
                      height: 100,
                      child: Text("$i"),
                    ),
                  ),
                  separatorBuilder: (context, index) {
                    return Container(
                      height: 0.5,
                      color: Colors.greenAccent,
                    );
                  },
                  itemCount: data.length,
                ),
                onNotification: (n) {
                  if (n is ScrollUpdateNotification) {
                    if (n.metrics.extentAfter > 50 && !_loading) {
                      _loading = true;
                      Future.delayed(Duration(milliseconds: 2000))
                          .then((value) {
                        for (int i = 0; i < 10; i++) {
                          data.add("Item $i");
                        }
                        if (mounted) setState(() {});
                        WidgetsBinding.instance
                            .addPostFrameCallback((timeStamp) {
                          _loading = false;
                        });
                      });
                    }
                  }
                  return false;
                })));
  }
}

2021-09-07.11.25.53.mov

[darshankawar]

@ldhlfzysys
Thanks for the code sample. I tried it on latest stable but not sure exactly what the issue here or how to replicate. I tried by not releasing the touch while scrolling but didn't notice any unusual behavior.

89417.mov

[ldhlfzysys]

@ldhlfzysys
Thanks for the code sample. I tried it on latest stable but not sure exactly what the issue here or how to replicate. I tried by not releasing the touch while scrolling but didn't notice any unusual behavior.

89417.mov

First. fast draging sceen up and keep finger on screen like my video's mouse position.
Second. setstate the data. the list will jump to the last index. you can see the last is 9 and jump to 19 in my video.

[darshankawar]

Second. setstate the data.

Can you elaborate on this ?