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这是一个相关的堆栈溢出问题。

Flutter：Step 小部件无法容纳 Expanded

如果有人阅读@derek-lakin 的评论，就会得出结论，应该在步进器中使用一列，因为步进器是可滚动的。我正在做完全相同的事情，但是我面临一个问题，即列使 Text 小部件仅占用所需的空间，而不是整个屏幕宽度。如果我用 Material 小部件包装 Text 小部件并应用高程或颜色，我会注意到这一点。

我试图将 Expanded 小部件包裹在我的小部件列周围来解决这个问题。但是，我得到渲染错误。

有人可以告诉我，我如何构建一个步进器，其步骤由层次结构组成为 Expanded(Column(children:List[Widgets]))。

我能够仅使用列构建步进器，但我正在考虑使用扩展来纠正列中不适当的大小问题

stepWidget = Expanded(
      child: Column(
    crossAxisAlignment: CrossAxisAlignment.start,
    children: widgets, //List of my widgets
  ));

这给出了以下错误：

    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.
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1 回答 1

2

根据错误： Expanded widgets must be placed directly inside Flex widgets.

为什么？根据文档：

Expanded 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 StatelessWidget 或 StatefulWidget（而不是其他类型的小部件，如 RenderObjectWidgets）。

您可以将Expanded小部件放入Column其中并将其Column放入您的Step小部件中，但您不能Expanded直接放入Step小部件的content.

一旦您提供完整的代码为您提供解决方案，我将更新我的答案。

到那时，这是你可以做的。

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.
    ]
 )
)
于 2018-11-28T08:26:14.583 回答