Flutter Web滚动-可滚动小部件错误

Question

我有一个用于飘动卷筒纸的屏幕，具有两列。一个是固定的（内容不滚动），另一个包含ListView（滚动）。我正在尝试捕获固定部分上的手势偏移，以使用Scrollable Widget同步ListView滚动。但是我遇到一个错误，该错误没有提供太多信息。

这是我正在使用的代码。

 SafeArea(
      child: Scaffold(
        backgroundColor: AppTheme.primaryBackgroundColor,
        body: Row(
                children: [
                  Expanded(
                    flex: 2,
                    child: Scrollable(
                        dragStartBehavior: DragStartBehavior.start,
                        axisDirection: _getDirection(context),
                        viewportBuilder: (BuildContext context, ViewportOffset position) {
                          return FixedPage(
                              width: isDesktop ? fullWidth / 2 : fullWidth, height: fullHeight);
                        },
                      ),
                    ),
                  ),
                  Expanded(
                    flex:3,
                    child: ListView(
                      controller: _scrollController,
                      children: [
                        Container(
                          constraints:
                              BoxConstraints.expand(width: fullWidth, height: fullHeight - 100),
                          color: Colors.blueAccent,
                        ),
                        Container(
                          constraints:
                              BoxConstraints.expand(width: fullWidth, height: fullHeight - 100),
                          color: Colors.redAccent,
                        ),
                        Container(
                          constraints:
                              BoxConstraints.expand(width: fullWidth, height: fullHeight - 100),
                          color: Colors.greenAccent,
                        ),
                        Container(
                          constraints:
                              BoxConstraints.expand(width: fullWidth, height: fullHeight - 100),
                          color: Colors.purpleAccent,
                        ),
                        FooterPage(),
                      ],
                    ),
                  ),
                ],
              ),
      ),
    );
  }

  AxisDirection _getDirection(BuildContext context) {
    return getAxisDirectionFromAxisReverseAndDirectionality(context, Axis.vertical, false);
  }

错误

════════ Exception caught by gesture library ═══════════════════════════════════════════════════════
The following ArgumentError was thrown while dispatching a pointer event:
Invalid argument: null

When the exception was thrown, this was the stack: 
dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 214:49      throw_
dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 13:3        argumentError
packages/flutter/src/widgets/scrollable.dart 584:21                               [_targetScrollOffsetForPointerScroll]
packages/flutter/src/widgets/scrollable.dart 590:41                               [_receivedPointerSignal]
packages/flutter/src/rendering/proxy_box.dart 2643:29                             handleEvent
...
Event: PointerScrollEvent#7c8f4(position: Offset(431.0, 312.0), scrollDelta: Offset(-0.0, 0.5))
  position: Offset(431.0, 312.0)
  scrollDelta: Offset(-0.0, 0.5)
Target: RenderPointerListener#a2d5b relayoutBoundary=up3
  needs compositing
  parentData: <none> (can use size)
  constraints: BoxConstraints(w=480.0, 0.0<=h<=754.0)
  size: Size(480.0, 754.0)
  behavior: deferToChild
  listeners: signal
════════════════════════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by gesture library ═══════════════════════════════════════════════════════
Invalid argument: null
════════════════════════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by gesture library ═══════════════════════════════════════════════════════
Invalid argument: null
════════════════════════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by gesture library ═══════════════════════════════════════════════════════
Invalid argument: null
════════════════════════════════════════════════════════════════════════════════════════════════════