Incorrect use of ParentDataWidget當我使用小部件時發生錯誤Expanded，如下所示，我在這里做錯了什么？還有，ownership chain意義何在？
代碼如下，
Expanded(
child: Wrap(
alignment: WrapAlignment.spaceAround,
children: <Widget>[
Expanded(
child: Row(
crossAxisAlignment: CrossAxisAlignment.center,
verticalDirection: VerticalDirection.down,
children: <Widget>[
Text(
"${Constants.ASSIGNMENT_PREFIX} ${assignment?.id}",
style: Theme.of(context)
.textTheme
.headline6),
_getAssignState(
assignment?.status),
],
),
),
],
),
)
完全錯誤如下，
======== Exception caught by widgets library =======================================================
The following assertion was thrown while applying parent data.:
Incorrect use of ParentDataWidget.
The ParentDataWidget Expanded(flex: 1) wants to apply ParentData of type FlexParentData to a RenderObject, which has been set up to accept ParentData of incompatible type WrapParentData.
Usually, this means that the Expanded widget has the wrong ancestor RenderObjectWidget. Typically, Expanded widgets are placed directly inside Flex widgets.
The offending Expanded is currently placed inside a Wrap widget.
The ownership chain for the RenderObject that received the incompatible parent data was:
Row ← Expanded ← Wrap ← Expanded ← Row ← Padding ← Padding ← DecoratedBox ← Container ← Listener ← ?
When the exception was thrown, this was the stack:
#0 RenderObjectElement._updateParentData.<anonymous closure> (package:flutter/src/widgets/framework.dart:5723:11)
#1 RenderObjectElement._updateParentData (package:flutter/src/widgets/framework.dart:5739:6)
#2 RenderObjectElement.attachRenderObject (package:flutter/src/widgets/framework.dart:5761:7)
#3 RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5440:5)
#4 MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:6228:11)
...
====================================================================================================
Reloaded 1 of 2005 libraries in 1,286ms.
uj5u.com熱心網友回復：
您只能用作和或小部件Expanded的子級。ColumnRowFLex
Expanded：擴展 Row、Column 或 Flex 的子項以使子項填充可用空間的小部件。
child: Wrap(
alignment: WrapAlignment.spaceAround,
children: <Widget>[
// Expanded( => remove this
Row()
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