Flutter 断言失败：第423行第16位：'；车身最大高度<；=I/flatter（29780）：math.max（0.0，looseConstraints.maxHeight-contentTop）和#x27；：事实并非如此

我有一个StatefullWidget，其中包含一个Scaffold，一个Scrollview，一个底部appbar，带有一个包含FloatingActionButton的凹口

随机滚动时，会抛出以下断言错误：

I/flutter (29780): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (29780): The following assertion was thrown during performLayout():
I/flutter (29780): 'package:flutter/src/material/scaffold.dart': Failed assertion: line 423 pos 16: 'bodyMaxHeight <=
I/flutter (29780): math.max(0.0, looseConstraints.maxHeight - contentTop)': is not true.
I/flutter (29780): 
I/flutter (29780): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter (29780): more information in this error message to help you determine and fix the underlying cause.
I/flutter (29780): In either case, please report this assertion by filing a bug on GitHub:
I/flutter (29780):   https://github.com/flutter/flutter/issues/new?template=BUG.md
I/flutter (29780): 
I/flutter (29780): When the exception was thrown, this was the stack:
I/flutter (29780): #2      _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:423:16)
I/flutter (29780): #3      MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:212:7)
I/flutter (29780): #4      RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:356:14)
I/flutter (29780): #5      RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1519:7)
I/flutter (29780): #6      PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:766:18)
I/flutter (29780): #7      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:347:19)
I/flutter (29780): #8      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:701:13)
I/flutter (29780): #9      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:286:5)
I/flutter (29780): #10     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1012:15)
I/flutter (29780): #11     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:952:9)
I/flutter (29780): #12     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:864:5)
I/flutter (29780): #16     _invoke (dart:ui/hooks.dart:219:10)
I/flutter (29780): #17     _drawFrame (dart:ui/hooks.dart:178:3)
I/flutter (29780): (elided 5 frames from class _AssertionError and package dart:async)
I/flutter (29780): 
I/flutter (29780): The following RenderObject was being processed when the exception was fired:
I/flutter (29780):   RenderCustomMultiChildLayoutBox#0211b NEEDS-LAYOUT NEEDS-PAINT
I/flutter (29780):   creator: CustomMultiChildLayout ← AnimatedBuilder ← DefaultTextStyle ← AnimatedDefaultTextStyle ←
I/flutter (29780):   _InkFeatures-[GlobalKey#fe169 ink renderer] ← NotificationListener<LayoutChangedNotification> ←
I/flutter (29780):   PhysicalModel ← AnimatedPhysicalModel ← Material ← PrimaryScrollController ← _ScaffoldScope ←
I/flutter (29780):   Scaffold ← ⋯
I/flutter (29780):   parentData: <none> (can use size)
I/flutter (29780):   constraints: BoxConstraints(w=411.4, h=683.4)
I/flutter (29780):   size: Size(411.4, 683.4)
I/flutter (29780): This RenderObject had the following descendants (showing up to depth 5):
I/flutter (29780):   _RenderLayoutBuilder#c4759 relayoutBoundary=up1
I/flutter (29780):     RenderConstrainedBox#f3db9 relayoutBoundary=up2
I/flutter (29780):       RenderRepaintBoundary#7768d NEEDS-PAINT
I/flutter (29780):         RenderCustomPaint#4fd8f NEEDS-PAINT
I/flutter (29780):           RenderRepaintBoundary#3b2ce
I/flutter (29780):   RenderConstrainedBox#f158f relayoutBoundary=up1 NEEDS-PAINT
I/flutter (29780):     RenderPhysicalShape#9331d NEEDS-PAINT
I/flutter (29780):       RenderCustomPaint#26663 NEEDS-PAINT
I/flutter (29780):         _RenderInkFeatures#a489b NEEDS-PAINT
I/flutter (29780):           RenderPadding#db65e NEEDS-PAINT
I/flutter (29780):   RenderStack#80cab relayoutBoundary=up1
I/flutter (29780):     RenderTransform#033b9 relayoutBoundary=up2
I/flutter (29780):       RenderTransform#b621a relayoutBoundary=up3
I/flutter (29780):         RenderSemanticsAnnotations#56fe9 relayoutBoundary=up4
I/flutter (29780):           _RenderInputPadding#e9ac7 relayoutBoundary=up5
I/flutter (29780): ════════════════════════════════════════════════════════════════════════════════════════════════════

当删除此标志时，不再发生错误，但如上所述，这不是我们的选项

我们创建了一个示例代码，以尽可能小的规模复制错误：

导入“包装：颤振/材料.省道”；
导入“package:flatter/rendering.dart”；
void main（）=>runApp（MyApp（））；
类MyApp扩展了无状态小部件{
@凌驾
小部件构建（构建上下文）{
返回材料PP(
主页：MyHomePage（），
);
}
}
类MyHomePage扩展StatefulWidget{
@凌驾
MyHomePageState createState（）=>MyHomePageState（）；
}
类MyHomePageState扩展了状态{
ScrollController\u ScrollController；
bool_visible=真；
@凌驾
void initState（）{
super.initState（）；
_scrollController=scrollController（）；
_scrollController.addListener（（）{
如果（_scrollController.position.userScrollDirection==
滚动方向（反向）{
设置状态（）{
_可见=假；
});
}
如果（_scrollController.position.userScrollDirection==
滚动方向（前进）{
设置状态（）{
_可见=真实；
});
}
});
}
@凌驾
小部件构建（构建上下文）{
double _bottomAppBarHeight=MediaQuery.of（context）.size.width*0.1；
返回脚手架(
扩展体：是的，
主体：容器(
宽度：MediaQuery.of（context）.size.width，
高度：MediaQuery.of（context）.size.height，
子：SingleChildScrollView(
控制器：\ u滚动控制器，
子：列(
儿童：[
文本（“顶部”），
容器(
颜色：颜色，红色，
高度：MediaQuery.of（context）.size.height，
),
文本（“底部”），
],
),
),
),
底部导航栏：动画容器(
持续时间：持续时间（毫秒：300），
曲线：曲线。线性，
高度：_可见？_底部AppBar高度：0.0，
子项：BottomAppBar(
颜色：颜色。绿色，
形状：CircularNotchedRectangle（），
孩子：我的钮扣(
按下：（）{}，
图标：图标（图标菜单），
),
),
),
浮动操作按钮：浮动操作按钮(
按下：（）{}，
子：图标（Icons.add），
),
floatingActionButtonLocation:floatingActionButtonLocation.centerDocked，
);
}
}

我们目前的颤振版本是：

Flutter (Channel stable, v1.5.4-hotfix.2, on Microsoft Windows [Version 10.0.17134.799], locale de-DE)

这实际上是颤振本身的问题，还是我们只是错过了一些重要的东西

更新

我们在GitHub的颤振回购协议中创建了一个问题：

Flutter (Channel stable, v1.5.4-hotfix.2, on Microsoft Windows [Version 10.0.17134.799], locale de-DE)