ParentWidget 的使用不正确。展开的小部件必须放在 flex 小部件内
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【中文标题】ParentWidget 的使用不正确。展开的小部件必须放在 flex 小部件内【英文标题】：Incorrect use of ParentWidget. Expanded widgets must be placed inside flex widget 【发布时间】：2020-08-29 08:54:00 【问题描述】：Widget build(BuildContext context)
return Scaffold(
backgroundColor:Colors.white,
body:Expanded(
child: Column(
children: <Widget>[
Container(
child: Column(
children: <Widget>[
Container(
width: MediaQuery.of(context).size.width*0.9,
height: MediaQuery.of(context).size.height*0.22,
color: Colors.white,
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
SizedBox(height: 36.0,),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text("MON COMPTE",style: TextStyle(fontSize:30,fontWeight:FontWeight.bold),),
Container(
height: 50.0,
width: 50.0,
child: FloatingActionButton(
backgroundColor: Color(0xffd57031),
onPressed: ()
,
child: Icon(Icons.help_outline,size: 30.0,),),
),
],
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Container(
decoration: BoxDecoration(
border:Border(bottom: BorderSide(color: Color(0xffd57031),width: check?3.0:1.0))
),
width: MediaQuery.of(context).size.width/2.2,
child: FlatButton(onPressed: ()
setState(()
check = true;
);
ctrl.animateToPage(0, duration: Duration(milliseconds: 200), curve: Curves.fastOutSlowIn);
, child: Text("Se connecter",style:TextStyle(color: Color(0xffd57031),fontSize: 20,fontWeight: FontWeight.bold)))),
Container(
decoration: BoxDecoration(
border:Border(bottom: BorderSide(color: Color(0xffd57031),width: check?1.0:3.0))
),
width: MediaQuery.of(context).size.width/2.31,
child: FlatButton(onPressed: ()
setState(()
check = false;
);
ctrl.animateToPage(1, duration: Duration(milliseconds: 200), curve: Curves.fastOutSlowIn);
, child: Text("S'inscrire",style:TextStyle(color: Color(0xffd57031),fontSize: 20,fontWeight: FontWeight.bold)))),
],
)
],
),
),
Container(
height:MediaQuery.of(context).size.height*0.78,
child: PageView(
controller: ctrl,
children: <Widget>[
Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
SizedBox(height:20.0),
txtField("E-mail"),
SizedBox(height:20.0),
txtField("Mot de passe"),
SizedBox(height:40.0),
Container(
decoration: BoxDecoration(
boxShadow: [
BoxShadow(
color: Colors.black12,
blurRadius: 20.0,
spreadRadius: 5.0
)
],
),
width: MediaQuery.of(context).size.width*0.7,
height: 50.0,
child: FlatButton(onPressed: (), child: Text("Se connecter",style: TextStyle(color:Colors.white,)),color: Color(0xffd57031),)),
SizedBox(height:40.0),
Text('Mot de passe oublié ?',style: TextStyle(color:Color(0xffd57031),),),
Divider(color: Color(0xffd57031),thickness: 1.5,indent: 112.0,endIndent: 125,height:1,)
],
),
),
],
),
)
],
),
),
],
),
),
);
并且有错误 I/flutter (20272)：══╡ 小部件库发现异常╞═════════════════════════════════════════ ═════════════════════════ I/flutter (20272)：在构建 _BodyBuilder 时抛出了以下断言： I/flutter (20272)：ParentDataWidget 使用不正确。 I/flutter (20272)：扩展的小部件必须放在 Flex 小部件内。 I/flutter (20272): Expanded(no depth, flex: 1, dirty) 根本没有 Flex 祖先。 I/flutter (20272)：违规扩展的父级的所有权链是： I/flutter (20272)：_BodyBuilder ← MediaQuery ← LayoutId-[<_scaffoldslot.body>] ← CustomMultiChildLayout ← I/flutter (20272): AnimatedBuilder ← DefaultTextStyle ← AnimatedDefaultTextStyle ← _InkFeatures-[GlobalKey#9611b ink I/flutter (20272): 渲染器] ← NotificationListener ← PhysicalModel ← ⋯ 我/颤振（20272）： I/flutter (20272)：相关的导致错误的小部件是： I/flutter (20272): 脚手架文件:///Users/macbook/androidStudioProjects/monmercato/lib/Screens/Login.dart:37:12
【问题讨论】：
【参考方案1】：您收到错误是因为您使用Expanded 小部件来包装您的Column。
要解决此问题，请尝试：
1) 移除包裹Column 的Expanded 小部件
2) 如果您希望小部件采用屏幕高度，请移除 Expanded 小部件并用 Container 包裹您的 Column 小部件（给容器一个宽度和高度属性)
检查下面的代码，它工作正常：
Widget build(BuildContext context)
return Scaffold(
backgroundColor:Colors.white,
Container(
// give the container your preferred height here
height: MediaQuery.of(context).size.height,
// give the container your preferred width here
width: MediaQuery.of(context).size.width,
child: Column(
children: <Widget>[
Container(
child: Column(
children: <Widget>[
Container(
width: MediaQuery.of(context).size.width*0.9,
height: MediaQuery.of(context).size.height*0.22,
color: Colors.white,
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
SizedBox(height: 36.0,),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text("MON COMPTE",style: TextStyle(fontSize:30,fontWeight:FontWeight.bold),),
Container(
height: 50.0,
width: 50.0,
child: FloatingActionButton(
backgroundColor: Color(0xffd57031),
onPressed: ()
,
child: Icon(Icons.help_outline,size: 30.0,),),
),
],
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Container(
decoration: BoxDecoration(
border:Border(bottom: BorderSide(color: Color(0xffd57031),width: check?3.0:1.0))
),
width: MediaQuery.of(context).size.width/2.2,
child: FlatButton(onPressed: ()
setState(()
check = true;
);
ctrl.animateToPage(0, duration: Duration(milliseconds: 200), curve: Curves.fastOutSlowIn);
, child: Text("Se connecter",style:TextStyle(color: Color(0xffd57031),fontSize: 20,fontWeight: FontWeight.bold)))),
Container(
decoration: BoxDecoration(
border:Border(bottom: BorderSide(color: Color(0xffd57031),width: check?1.0:3.0))
),
width: MediaQuery.of(context).size.width/2.31,
child: FlatButton(onPressed: ()
setState(()
check = false;
);
ctrl.animateToPage(1, duration: Duration(milliseconds: 200), curve: Curves.fastOutSlowIn);
, child: Text("S'inscrire",style:TextStyle(color: Color(0xffd57031),fontSize: 20,fontWeight: FontWeight.bold)))),
],
)
],
),
),
Container(
height:MediaQuery.of(context).size.height*0.78,
child: PageView(
controller: ctrl,
children: <Widget>[
Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
SizedBox(height:20.0),
txtField("E-mail"),
SizedBox(height:20.0),
txtField("Mot de passe"),
SizedBox(height:40.0),
Container(
decoration: BoxDecoration(
boxShadow: [
BoxShadow(
color: Colors.black12,
blurRadius: 20.0,
spreadRadius: 5.0
)
],
),
width: MediaQuery.of(context).size.width*0.7,
height: 50.0,
child: FlatButton(onPressed: (), child: Text("Se connecter",style: TextStyle(color:Colors.white,)),color: Color(0xffd57031),)),
SizedBox(height:40.0),
Text('Mot de passe oublié ?',style: TextStyle(color:Color(0xffd57031),),),
Divider(color: Color(0xffd57031),thickness: 1.5,indent: 112.0,endIndent: 125,height:1,)
],
),
),
],
),
)
],
),
),
],
),
),
);
我希望这会有所帮助。
【讨论】：
【参考方案2】：您只需删除 First Expanded Widget。
Scaffold(
backgroundColor: Colors.white,
body: Column(// remove Expandede
children: <Widget>[
【讨论】：
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