boundcing scroll offset

[yyong37]

预期: 下拉回弹会定位到顶部第一个元素. 但是现在会回弹至第2,3个元素才停止

expect: bouncing and stop edge first item

----screen top edge-----
------  <-- expect stop position
-------
------- <-- current version stop scroll offset
-------
------- 

class BingoPage extends StatefulWidget {
  @override
  State<BingoPage> createState() => _BingoPageState();
}

class _BingoPageState extends State<BingoPage> {
  final logic = Get.find<BingoLogic>();

  final data = <String>[];

  @override
  void initState() {
    // mock chat list insert data
    Timer.periodic(Duration(seconds: 1), (timer) {
      setState(() {
        data.insert(0, DateTime.now().toString());
      });
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: FlutterListView(
            reverse: true,
            delegate: FlutterListViewDelegate(
              (BuildContext context, int index) => ListTile(title: Text('List Item ${data[index]}')),
              childCount: data.length,
              keepPosition: true,
            )));
  }
}

[robert-bitguild]

@rizzi37 I can't reproduce the issue that you mentioned. Please copy/paste the whole FlutterListView element to me to verify it.

1. Did you have set reverse to true,
2. Did you have wrap SmartRefresher or other refresh element on it.

[yyong37]

@robert-bitguild thanks for your fast reply, I have updated my origin issue with the same code.

[robert-bitguild]

@rizzi37 我认为这个是正常行为，我对比了ListView的官方源码(ListView也有这个问题)，这是因为你在下拉过程中，Timer.periodic(Duration(seconds: 1), (timer) 里创建了新的项而导致滚动后退了。现实情况下，这种情况一般不会考虑，即下拉过程中有UI刷新。

另外，keepPosition: true时最好实现 onItemKey: (index) ，否测keepPosition不会成效。因为我不知道你insert的行在那里。onItemKey要返加该行的唯一值。

  return Scaffold(
        body: FlutterListView(
            reverse: true,
            delegate: FlutterListViewDelegate(
              (BuildContext context, int index) =>
                  ListTile(title: Text('List Item ${data[index]}')),
              childCount: data.length,
              keepPosition: true,
              onItemKey: (index) {
                return data[index];
              },
            )));

[yyong37]

收到.再次表示感谢.