这是一个相关的堆栈溢出问题。
Flutter : Step widget can not hold Expanded
如果阅读@ derek-lakin注释，则得出结论，应该在步进器内使用一列，因为步进器是可滚动的。我正在做完全相同的事情，但是我遇到一个问题，即列使Text小部件仅占用所需的空间，而不占用整个屏幕宽度。如果将“文字”小部件与“材质”小部件包装在一起并应用高程或颜色，我会注意到这一点。
我尝试将扩展的小部件包装在我的小部件列周围，以解决此问题。但是，我得到渲染错误。
有人可以让我知道，我该如何构建一个步进器，其步阶由Expanded（Column（children：List [Widgets]））组成。
我仅能使用列来构建步进器，但是我正在考虑使用expand来纠正列中不适当的尺寸问题
stepWidget = Expanded(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: widgets, //List of my widgets
));
这会出现以下错误：
I/flutter (19635): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (19635): The following assertion was thrown building NotificationListener<KeepAliveNotification>:
I/flutter (19635): Incorrect use of ParentDataWidget.
I/flutter (19635): Expanded widgets must be placed directly inside Flex widgets.
I/flutter (19635): Expanded(no depth, flex: 2, dirty) has a Flex ancestor, but there are other widgets between them:
I/flutter (19635): - RepaintBoundary-[<0>]
I/flutter (19635): - IndexedSemantics(index: 0)
I/flutter (19635): - KeepAlive(keepAlive: false)
I/flutter (19635): - SliverList(delegate: SliverChildListDelegate#de272(estimated child count: 1))
I/flutter (19635): - SliverPadding(padding: EdgeInsets.zero)
I/flutter (19635): - ShrinkWrappingViewport(axisDirection: down, offset: ScrollPositionWithSingleContext#83fdf(offset:
I/flutter (19635): 0.0, range: null..null, viewport: null, ScrollableState, ClampingScrollPhysics,
I/flutter (19635): IdleScrollActivity#b00f3, ScrollDirection.idle))
I/flutter (19635): - IgnorePointer-[GlobalKey#88af5](ignoring: false, ignoringSemantics: false)
I/flutter (19635): - Semantics(container: false, properties: SemanticsProperties, label: null, value: null, hint: null,
I/flutter (19635): hintOverrides: null)
I/flutter (19635): - Listener(listeners: [down], behavior: opaque)
I/flutter (19635): - _GestureSemantics
I/flutter (19635): - _ScrollSemantics-[GlobalKey#81c78]
I/flutter (19635): - RepaintBoundary
I/flutter (19635): - CustomPaint
I/flutter (19635): - RepaintBoundary
I/flutter (19635): - Expanded(flex: 1) (this is a different Expanded than the one with the problem)
I/flutter (19635): These widgets cannot come between a Expanded and its Flex.
I/flutter (19635): The ownership chain for the parent of the offending Expanded was:
I/flutter (19635): RepaintBoundary-[<0>] ← IndexedSemantics ← NotificationListener<KeepAliveNotification> ← KeepAlive
I/flutter (19635): ← AutomaticKeepAlive ← SliverList ← MediaQuery ← SliverPadding ← ShrinkWrappingViewport ←
I/flutter (19635): _ScrollableScope ← ⋯
I/flutter (19635):
I/flutter (19635): When the exception was thrown, this was the stack:
I/flutter (19635): #0 ParentDataElement.mount.<anonymous closure> (package:flutter/src/widgets/framework.dart:4015:7)
I/flutter (19635): #1 ParentDataElement.mount (package:flutter/src/widgets/framework.dart:4024:6)
I/flutter (19635): #2 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
I/flutter (19635): #3 Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
I/flutter (19635): #4 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4838:14)
I/flutter (19635): #5 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
I/flutter (19635): #6 Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
I/flutter (19635): #7 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4838:14)
I/flutter (19635): #8 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
I/flutter (19635): #9 Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
I/flutter (19635): #10 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3710:16)
I/flutter (19635): #11 Element.rebuild (package:flutter/src/widgets/framework.dart:3547:5)
I/flutter (19635): #12 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3679:5)
I/flutter (19635): #13 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3674:5)
I/flutter (19635): #14 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
I/flutter (19635): #15 Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
I/flutter (19635): #16 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3710:16)
I/flutter (19635): #17 Element.rebuild (package:flutter/src/widgets/framework.dart:3547:5)
I/flutter (19635): #18 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3679:5)
I/flutter (19635): #19 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3674:5)
I/flutter (19635): #20 ParentDataElement.mount (package:flutter/src/widgets/framework.dart:4025:11)
I/flutter (19635): #21 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
I/flutter (19635): #22 Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
I/flutter (19635): #23 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3710:16)
I/flutter (19635): #24 Element.rebuild (package:flutter/src/widgets/framework.dart:3547:5)
I/flutter (19635): #25 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3679:5)
I/flutter (19635): #26 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3826:11)
I/flutter (19635): #27 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3674:5)
I/flutter (19635): #28 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
I/flutter (19635): #29 Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
I/flutter (19635): #30 SliverMultiBoxAdaptorElement.updateChild (package:flutter/src/widgets/sliver.dart:1012:36)
I/flutter (19635): #31 SliverMultiBoxAdaptorElement.createChild.<anonymous closure> (package:flutter/src/widgets/sliver.dart:997:20)
I/flutter (19635): #32 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2266:19)
I/flutter (19635): #33 SliverMultiBoxAdaptorElement.createChild (package:flutter/src/widgets/sliver.dart:990:11)
I/flutter (19635): #34 RenderSliverMultiBoxAdaptor._createOrObtainChild.<anonymous closure> (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:256:23)
I/flutter (19635): #35 RenderObject.invokeLayoutCallback.<anonymous closure> (package:flutter/src/rendering/object.dart:1730:58)
I/flutter (19635): #36 PipelineOwner._enableMutationsToDirtySubtrees (package:flutter/src/rendering/object.dart:799:15)
I/flutter (19635): #37 RenderObject.invokeLayoutCallback (package:flutter/src/rendering/object.dart:1730:13)
I/flutter (19635): #38 RenderSliverMultiBoxAdaptor._createOrObtainChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:245:5)
I/flutter (19635): #39 RenderSliverMultiBoxAdaptor.addInitialChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:323:5)
I/flutter (19635): #40 RenderSliverList.performLayout (package:flutter/src/rendering/sliver_list.dart:78:12)
I/flutter (19635): #41 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #42 RenderSliverPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:182:11)
I/flutter (19635): #43 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #44 RenderViewportBase.layoutChildSequence (package:flutter/src/rendering/viewport.dart:405:13)
I/flutter (19635): #45 RenderShrinkWrappingViewport._attemptLayout (package:flutter/src/rendering/viewport.dart:1645:12)
I/flutter (19635): #46 RenderShrinkWrappingViewport.performLayout (package:flutter/src/rendering/viewport.dart:1608:20)
I/flutter (19635): #47 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #48 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (19635): #49 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #50 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (19635): #51 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #52 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (19635): #53 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #54 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (19635): #55 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #56 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (19635): #57 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #58 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (19635): #59 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #60 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (19635): #61 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #62 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (19635): #63 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #64 RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:798:17)
I/flutter (19635): #65 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (19635): #66 MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:142:11)
I/flutter (19635): #67 _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:339:7)
I/flutter (19635): #68 MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:212:7)
I/flutter (19635): #69 RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:356:14)
I/flutter (19635): #70 RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1509:7)
I/flutter (19635): #71 PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:768:18)
I/flutter (19635): #72 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:281:19)
I/flutter (19635): #73 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:677:13)
I/flutter (19635): #74 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:219:5)
I/flutter (19635): #75 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter (19635): #76 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter (19635): #77 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
I/flutter (19635): #78 _invoke (dart:ui/hooks.dart:151:13)
I/flutter (19635): #79 _drawFrame (dart:ui/hooks.dart:140:3)
I/flutter (19635): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter (19635): Another exception was thrown: 'package:flutter/src/rendering/sliver_multi_box_adaptor.dart': Failed assertion: line 217 pos 16: 'indexOf(child) > index': is not true.
I/flutter (19635): Another exception was thrown: 'package:flutter/src/rendering/sliver_multi_box_adaptor.dart': Failed assertion: line 217 pos 16: 'indexOf(child) > index': is not true.
I/flutter (19635): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 2270 pos 20: '_debugCurrentBuildTarget == context': is not true.
I/flutter (19635): Another exception was thrown: NoSuchMethodError: The getter 'scrollOffsetCorrection' was called on null.
I/flutter (19635): Another exception was thrown: NoSuchMethodError: The method 'debugAssertIsValid' was called on null.
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: RenderShrinkWrappingViewport#44117 relayoutBoundary=up10 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: RenderIgnorePointer#7c8dd relayoutBoundary=up9 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#f736b relayoutBoundary=up8 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: RenderPointerListener#3760f relayoutBoundary=up7 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: RenderSemanticsGestureHandler#860e2 relayoutBoundary=up6 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: _RenderScrollSemantics#b1734 relayoutBoundary=up5 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#d9292 relayoutBoundary=up4 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: RenderCustomPaint#44461 relayoutBoundary=up3 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#4425c relayoutBoundary=up2 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: RenderBox was not laid out: RenderFlex#e5d03 relayoutBoundary=up1 NEEDS-PAINT
I/flutter (19635): Another exception was thrown: NoSuchMethodError: The method '<=' was called on null.
答案 0 :(得分：1)
根据错误：Expanded
为什么？ 根据{{3}}：
扩展小部件必须是Row，Column或Flex的后代，并且从Expanded小部件到其封闭的Row，Column或Flex的路径必须仅包含StatelessWidgets或StatefulWidgets（不能包含其他类型的小部件，例如RenderObjectWidgets ）。
您可以将Column小部件放在Column内，然后将Step放在Expanded小部件内，但是不能将Step直接放在{{ 1}}小部件的content。
一旦您提供完整的代码以为您提供解决方案，我将更新答案。
到那时，这就是你可以做的。
Container(
width: double.infinity, //To make it use as much space as it wants
height: whateverHeightYouWantTo,
child: Column(
children: <Widget>[
Expanded(child: Widget()) //You'll probably won't need Expanded by now.
]
)
)