在 Stackoverflow 上找了一圈也没有找到答案，想向 v2 的朋友们求助一下。

NestedScrollView + SliverAppBar + TabView 与Scrollbar合用，在左右滑动时出现以下错误：

The following assertion was thrown while notifying status listeners for AnimationController: The PrimaryScrollController is currently attached to more than one ScrollPosition.

我尝试过用PrimaryScrollController包裹Scroller 组件，错误不再出现，但是NestedScrollView上下两边的滚动不再同步；尝试过写NotificationListener，问题看起来解决了，但是会有奇怪的卡顿现象：

NotificationListener<ScrollNotification>(             onNotification: (ScrollNotification notification) {               //print(notification.metrics.axisDirection);               if (notification.metrics.extentAfter > 0 &&                   notification.metrics.extentBefore > 0 &&                   notification.metrics.axisDirection == AxisDirection.down) {                 double pixelnow = notification.metrics.pixels;                 double _jmpTo =                     _scrollController.offset + (pixelnow - _scrollLocation);                 //print("pixel now : $pixelnow");                 //print("jumpto: $_jmpTo");                 if (_scrollController.position.maxScrollExtent >= _scrollController.offset                    && _scrollController.offset >= _scrollController.position.minScrollExtent ){                   _scrollController.jumpTo(_jmpTo);                   //_scrollController.jumpTo(value)                 }                 _scrollLocation = pixelnow;               }               return false;             }, 

我的原始代码如下：

 import 'package:flutter/material.dart';  void main() => runApp(MaterialApp(home: Scaffold(body: CommunityPage())));  class CommunityPage extends StatefulWidget {   CommunityPage({Key? key}) : super(key: key);    @override   _CommunityPageState createState() => _CommunityPageState(); }  class _CommunityPageState extends State<CommunityPage> {   //ScrollController _scrollController = ScrollController();   //final TabController _tabController = TabController();   final _tabs = <String>["Tab 1", "Tab 2", "Tab 3"];    @override   Widget build(BuildContext context) {     return Scaffold(       body: DefaultTabController(         length: _tabs.length, // This is the number of tabs.         child: NestedScrollView(           headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {             // These are the slivers that show up in the "outer" scroll view.             return <Widget>[               SliverOverlapAbsorber(                 handle:                     NestedScrollView.sliverOverlapAbsorberHandleFor(context),                 sliver: SliverAppBar(                   automaticallyImplyLeading: false,                   title: const Text("Community",style: TextStyle(color: Colors.black)),                   //centerTitle: false,                   pinned: true,                   floating: true,                   snap: true,                   backgroundColor: Colors.grey[50],                   expandedHeight: 85.0,                    bottom: TabBar(                     tabs: _tabs.map((String name) => Tab(text: name)).toList(),                   ),                 ),               ),             ];           },           body: TabBarView(             children: _tabs.map((String name) {               //SafeArea 适配刘海屏的一个 widget               return Builder(                 builder: (BuildContext context) {                   return Scrollbar(                     child: CustomScrollView(                       key: PageStorageKey<String>(name),                       slivers: <Widget>[                         SliverOverlapInjector(                           handle:                               NestedScrollView.sliverOverlapAbsorberHandleFor(                                   context),                         ),                         SliverFixedExtentList(                           itemExtent: 50.0, //item 高度或宽度，取决于滑动方向                           delegate: SliverChildBuilderDelegate(                             (BuildContext context, int index) {                               return ListTile(                                 title: Text('Item $index'),                               );                             },                             childCount: 30,                           ),                         ),                       ],                     ),                   );                 },               );             }).toList(),           ),         ),       ),     );   } } 

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