我正在使用scrollable_positioned_list包，并让它呈现一个大的动态列表。它工作得很好。但是，我需要我的列表有一个滚动条（类似于this）。到目前为止，这是不可能的。
有人知道怎么做吗？
我的代码如下所示：

Scrollbar(
          child: ScrollablePositionedList.builder(
            physics: const ClampingScrollPhysics(
              parent: AlwaysScrollableScrollPhysics(),
            ),
            itemCount: posts.length + 1,
            itemBuilder: (context, index) {
              if (index == 0) {
                return Container(
                  height: 200,
                  color: Colors.green,
                  child: const Center(
                    child: Text('post content'),
                  ),
                );
              } else if (posts[index - 1].isRoot) {
                return Container(
                  padding: const EdgeInsets.symmetric(vertical: 15),
                  margin: const EdgeInsets.symmetric(vertical: 5),
                  color: Colors.redAccent,
                  child: Text('ROOT COMMENT, index: ${index - 1}'),
                );
              } else {
                return Container(
                  padding: const EdgeInsets.symmetric(vertical: 15),
                  margin: const EdgeInsets.symmetric(vertical: 5),
                  color: Colors.lightBlueAccent,
                  child: Text('Threaded comment, index: ${index - 1}'),
                );
              }
            },
            itemScrollController: itemScrollController,
            itemPositionsListener: itemPositionsListener,
          ),
        ),

我意识到ScrollBar需要与它所覆盖的滚动视图具有相同的ScrollController，但是，我不确定如何获得它，因为ScrollablePositionedList没有ScrollController。
使用提供的解决方案运行项目后，终端中出现错误（一小段）：

Performing hot restart...                           
../../tools/flutter/.pub-cache/git/flutter.widgets-6
d6dac5f19b577338d912d3c9a45d26593e0a475/packages/scr
ollable_positioned_list/lib/src/scrollable_positione
d_list.dart:437:24: Warning: Operand of null-aware
operation '!' has type 'SchedulerBinding' which
excludes null.
Performing hot restart...                           
 - 'SchedulerBinding' is from
 'package:flutter/src/scheduler/binding.dart'
 ('../../tools/flutter/packages/flutter/lib/src/sche
 duler/binding.dart').
Performing hot restart...                           
      SchedulerBinding.instance!.addPostFrameCallbac
      k((_) {
Performing hot restart...                           
                       ^
Performing hot restart...                           
../../tools/flutter/.pub-cache/git/flutter.widgets-6
d6dac5f19b577338d912d3c9a45d26593e0a475/packages/scr
ollable_positioned_list/lib/src/scrollable_positione
d_list.dart:484:26: Warning: Operand of null-aware
operation '!' has type 'SchedulerBinding' which
excludes null.
Performing hot restart...                           
 - 'SchedulerBinding' is from
 'package:flutter/src/scheduler/binding.dart'
 ('../../tools/flutter/packages/flutter/lib/src/sche
 duler/binding.dart').
Performing hot restart...                           
        SchedulerBinding.instance!.addPostFrameCallb
        ack((_) {
Performing hot restart...                           
                         ^
Performing hot restart...                           
../../tools/flutter/.pub-cache/git/flutter.widgets-6
d6dac5f19b577338d912d3c9a45d26593e0a475/packages/scr
ollable_positioned_list/lib/src/positioned_list.dart
:298:24: Warning: Operand of null-aware operation
'!' has type 'SchedulerBinding' which excludes null.
Performing hot restart...                           
 - 'SchedulerBinding' is from
 'package:flutter/src/scheduler/binding.dart'
 ('../../tools/flutter/packages/flutter/lib/src/sche
 duler/binding.dart').
Performing hot restart...                           
      SchedulerBinding.instance!.addPostFrameCallbac
      k((_) {
Performing hot restart...                           
                       ^
Performing hot restart...                                               
Restarted application in 195ms.

修复警告后（回复评论），现在使用时会随机出现这种情况：

The following assertion was thrown while notifying status listeners for AnimationController:
The Scrollbar's ScrollController has no ScrollPosition attached.
A Scrollbar cannot be painted without a ScrollPosition.
The Scrollbar attempted to use the provided ScrollController. This ScrollController should be
associated with the ScrollView that the Scrollbar is being applied to. When providing your
own
ScrollController, ensure both the Scrollbar and the Scrollable widget use the same one.

When the exception was thrown, this was the stack:
#0      RawScrollbarState._debugCheckHasValidScrollPosition.<anonymous closure>
(package:flutter/src/widgets/scrollbar.dart:1475:9)
#1      RawScrollbarState._debugCheckHasValidScrollPosition
(package:flutter/src/widgets/scrollbar.dart:1500:6)
#2      RawScrollbarState._validateInteractions
(package:flutter/src/widgets/scrollbar.dart:1445:14)
#3      AnimationLocalStatusListenersMixin.notifyStatusListeners
(package:flutter/src/animation/listener_helpers.dart:233:19)
#4      AnimationController._checkStatusChanged
(package:flutter/src/animation/animation_controller.dart:815:7)
#5      AnimationController._startSimulation
(package:flutter/src/animation/animation_controller.dart:749:5)
#6      AnimationController._animateToInternal
(package:flutter/src/animation/animation_controller.dart:612:12)
#7      AnimationController.reverse
(package:flutter/src/animation/animation_controller.dart:494:12)
#8      RawScrollbarState._maybeStartFadeoutTimer.<anonymous closure>
(package:flutter/src/widgets/scrollbar.dart:1630:37)
(elided 11 frames from class _RawReceivePortImpl, class _Timer, dart:async, and
dart:async-patch)

The AnimationController notifying status listeners was:
  AnimationController#72402(◀ 1.000)