当我使用ListView时，出现了“Incorrect use of ParentDataWidget”错误。

Question

在我的应用程序的这一部分中，我有一个 ListView，当我运行应用程序时，会出现以下错误，我无法解决它：

Scaffold(
  body: Directionality(
textDirection: TextDirection.rtl,
child: Container(
  child: StreamBuilder(
    stream: globals.database.ticketsDao.getTicketsStream(),
    builder: (BuildContext context, AsyncSnapshot<List<Tickets>> snapshot) {
      if (snapshot.hasData) {
        return Column(
          children: <Widget>[
            Expanded(
              child: ListView.separated(
                  itemBuilder: (context, index) {
                    return ListTile(
                      title: Flexible(
                        child: Text(
                          snapshot.data[index].subject,
                          style: Theme.of(context).textTheme.caption.copyWith(fontFamily: 'IranSansBold'),
                        ),
                      ),
                      subtitle: Text(
                        snapshot.data[index].description,
                        style: Theme.of(context).textTheme.caption.copyWith(fontFamily: 'IranSansLight'),
                      ),
                    );
                  },
                  separatorBuilder: (context, index) {
                    return Divider();
                  },
                  itemCount:  snapshot.data.length),
            ),
          ],
        );
      } else {
        return Container(
            child: Center(
          child: Text(
            Strings.notAnyTickets,),
          ),
        ));
      }
    },
  ),
),
));

错误：

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════  
The following assertion was thrown building DefaultTextStyle(debugLabel:
((englishLike subhead  2014).merge(blackMountainView

subhead)).copyWith, inherit: false, color: Color(0xdd000000), family:
Roboto, size: 16.0, weight: 400, baseline: alphabetic, decoration:
TextDecoration.none, softWrap:  wrapping at box width, overflow:
clip):  Incorrect use of ParentDataWidget.

Flexible widgets must be
placed directly inside Flex widgets.  Flexible(no depth, flex: 1,
dirty) has a Flex ancestor, but there are other widgets between them:
 - _ListTile

 - Padding(padding: EdgeInsets(16.0, 0.0, 16.0, 0.0))
 - Semantics(container: false, properties: SemanticsProperties, selected: false, label: null, value:  null, hint: null, hintOverrides:
null)

 - Listener(listeners: [down], behavior: opaque)
 - _GestureSemantics
 - Listener(listeners: <none behavior: translucent)
 - RepaintBoundary
 - IndexedSemantics(index: 0)
 - KeepAlive(keepAlive: false)
 - SliverList(delegate: SliverChildBuilderDelegate#6802e(estimated child count: 19))

 - SliverPadding(padding: EdgeInsets(0.0, 0.0, 0.0, 50.0))
 - Viewport(axisDirection: down, anchor: 0.0, offset: ScrollPositionWithSingleContext#c95ba(offset:
 0.0, range: null..null, viewport: 335.0, ScrollableState, AlwaysScrollableScrollPhysics - ClampingScrollPhysics,
IdleScrollActivity#05a39, ScrollDirection.idle))
 - IgnorePointer-[GlobalKey#a3d1a](ignoring: false, ignoringSemantics: false)

 - Semantics(container: false, properties: SemanticsProperties, label: null, value: null, hint: null,  hintOverrides: null)
 - Listener(listeners: [down], behavior: opaque)
 - _GestureSemantics

 - Listener(listeners: [signal], behavior: deferToChild)
 - _ScrollSemantics-[GlobalKey#7cd1b]
 - RepaintBoundary
 - CustomPaint
 - RepaintBoundary
 - Expanded(flex: 1)  These widgets cannot come between a Flexible and its Flex.  The ownership chain for the parent of the offending
Flexible was:    DefaultTextStyle ← AnimatedDefaultTextStyle ←
_ListTile ← MediaQuery ← Padding ← SafeArea ←  Semantics ← Listener ← _GestureSemantics ← RawGestureDetector ← ⋯

- DolDurma

Answer 1

灵活的小部件必须是Expanded或Flex小部件的直接子代。

在您的情况下，您正在使用Flexible作为ListTile小部件的一部分，这不是一个合适的父级。

灵活的小部件必须直接放置在Flex小部件内。

Flexible具有Flex祖先，但它们之间还有其他小部件: - _ListTile

- omar hatem

Answer 2

Flexible和Expanded可以有row、column或flex作为子元素，但不能使用与ListView相关的小部件。

如果您仍希望在小部件中使用扩展属性的相同效果，请使用ConstrainedBox

例如：

ConstrainedBox(
  constraints: BoxConstraints(minHeight: 50, maxHeight: 500),
  child: ListView.separated(...),
)

- Sanjay TM

Answer 3

对我来说，问题出在使用 Expanded 作为父部件。我不知不觉地添加了一个 Expanded：

 child: Expanded(
              child: Row(
                children: [
                  const SizedBox(
                    width: 15,
                  ),
                  Expanded().....
                  ])
                )

然后我移除了第一个扩展

 child:  Row(
                children: [
                  const SizedBox(
                    width: 15,
                  ),
                  Expanded().....
                  ]
                )

and prob solved!!!

- JoelSebstn

Answer 4

 Widget                      Parent Widget
Expanded()               Row(), Column(), Flex()
Flexible()               Row(), Column(), Flex()
Positioned()                    Stack()
TableCell()                     Table()

- AKASH PANARI

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你应该添加解释。 - Super Kai - Kazuya Ito