如何解决-如何解决：不正确使用ParentDataWidget？
我得到对ParentDataWidget的错误使用错误。
并且列表第一次没有显示该项目。
ParentDataWidget Expanded（flex：1）希望将FlexParentData类型的ParentData应用于RenderObject，该对象已设置为接受不兼容类型ParentData的ParentData。
通常，这意味着扩展窗口小部件的祖先RenderObjectWidget错误。通常，扩展小部件直接放置在Flex小部件内部。 令人反感的Expanded当前位于ConstrainedBox小部件内。
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
actions: <Widget>[
IconButton(
icon: Icon(Icons.shopping_cart),onPressed: () {},)
],backgroundColor: Colors.green,),drawer: Drawer(
child: AppDrawer(),body: SingleChildScrollView(
child: ConstrainedBox(
constraints: BoxConstraints(),child: Column(
children: <Widget>[
Container(
height: 200,width: double.infinity,child: HomeSlider(),Padding(
padding: EdgeInsets.only(top: 14.0,left: 8.0,right: 8.0),child: Text(
AppLocalizations.of(context)
.translate('leatest_producrs'),style: TextStyle(
color: Theme.of(context).accentColor,fontSize: 18,fontWeight: FontWeight.w700)),Container(
margin: EdgeInsets.symmetric(vertical: 8.0),height: 200.0,child: Expanded(
child: ListView.builder(
shrinkWrap: true,scrollDirection: Axis.horizontal,itemCount: cards.length,itemBuilder: (BuildContext context,int index) => Card(
child: InkWell(
child: Column(
children: [
Flexible(
child: Container(
height: double.infinity,width: 120,decoration: BoxDecoration(
image: DecorationImage(
image: NetworkImage(
cards[index].productImg,fit: BoxFit.fitHeight,)),Container(
width: 150,padding: EdgeInsets.all(10),child: Text(cards[index].productName,style: new TextStyle(fontSize: 12),softWrap: true),],onTap: () {
Fluttertoast.showToast(
msg: cards[index].productName,toastLength: Toast.LENGTH_SHORT,gravity: ToastGravity.BOTTOM,timeInSecForIosWeb: 1,backgroundColor: Colors.white70,textColor: Colors.black,fontSize: 16.0);
},Container(
child: Padding(
padding: EdgeInsets.only(top: 6.0,child: Image(
fit: BoxFit.cover,image: AssetImage('assets/images/banner-1.jpg'),Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,children: <Widget>[
Padding(
padding: EdgeInsets.only(top: 8.0,child: Text('Featured Products',style: TextStyle(
color: Theme.of(context).accentColor,Padding(
padding: const EdgeInsets.only(
right: 8.0,top: 8.0,left: 8.0),child: RaisedButton(
color: Theme.of(context).primaryColor,child: Text('View All',style: TextStyle(color: Colors.white)),onPressed: () {
Navigator.pushNamed(context,'/categorise');
}),)
],Container(
child: GridView.count(
shrinkWrap: true,physics: NeverScrollableScrollPhysics(),crossAxisCount: 2,padding:
EdgeInsets.only(top: 8,left: 6,right: 6,bottom: 12),children: List.generate(cards.length,(index) {
return Container(
child: Card(
clipBehavior: Clip.antiAlias,child: InkWell(
onTap: () {
print('Card tapped.');
},child: Column(
crossAxisAlignment: CrossAxisAlignment.start,children: <Widget>[
Flexible(
child: Container(
height: double.infinity,decoration: BoxDecoration(
image: DecorationImage(
image: NetworkImage(
cards[index].productImg,ListTile(
title: Text(
cards[index].productName,style: TextStyle(
fontWeight: FontWeight.w700,fontSize: 12),);
}),Container(
child: Padding(
padding: EdgeInsets.only(
top: 6.0,right: 8.0,bottom: 10),image: AssetImage('assets/images/banner-2.jpg'),)
],));
错误代码是
══╡ 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 ParentData.
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 ConstrainedBox widget.
The ownership chain for the RenderObject that received the incompatible parent data was:
RepaintBoundary ← NotificationListener<ScrollNotification> ← GlowingOverscrollIndicator ←
Scrollable ← ListView ← Expanded ← ConstrainedBox ← Padding ← Container ← Column ← ⋯
When the exception was thrown,this was the stack:
.
.
.
.
(elided 4 frames from class _RawReceivePortImpl,class _Timer,and dart:async-patch)
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ 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 ParentData.
Usually,Expanded widgets are placed directly inside Flex widgets.
The offending Expanded is currently placed inside a ConstrainedBox widget.
The ownership chain for the RenderObject that received the incompatible parent data was:
RepaintBoundary ← NotificationListener<ScrollNotification> ← GlowingOverscrollIndicator ← Scrollable ← ListView ← Expanded ← ConstrainedBox ← Padding ← Container ← Column ← ⋯
When the exception was thrown,this was the stack:
#0 RenderObjectElement._updateParentData.<anonymous closure> (package:flutter/src/widgets/framework.dart:5689:11)
#1 RenderObjectElement._updateParentData (package:flutter/src/widgets/framework.dart:5705:6)
#2 ParentDataElement._applyParentData.applyParentDataToChild (package:flutter/src/widgets/framework.dart:4939:15)
#3 ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:4600:14)
#4 ParentDataElement._applyParentData.applyParentDataToChild (package:flutter/src/widgets/framework.dart:4942:15)
...
════════════════════════════════════════════════════════════════════════════════════════════════════
解决方法
您可以在下面复制粘贴运行完整代码
就您而言，您不需要Expanded，因为您已经将Container height设置为200
代码段
Container(
margin: EdgeInsets.symmetric(vertical: 8.0),height: 200.0,child: ListView.builder(
工作演示
完整代码
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',theme: ThemeData(
primarySwatch: Colors.blue,visualDensity: VisualDensity.adaptivePlatformDensity,),home: MyHomePage(title: 'Flutter Demo Home Page'),);
}
}
class CardItem {
String productImg;
String productName;
CardItem({this.productImg,this.productName});
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key,this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
List<CardItem> cards = [
CardItem(productImg: "https://picsum.photos/250?image=9",productName: "a"),CardItem(
productImg: "https://picsum.photos/250?image=10",productName: "b"),CardItem(
productImg: "https://picsum.photos/250?image=11",productName: "c"),CardItem(
productImg: "https://picsum.photos/250?image=12",productName: "d"),CardItem(
productImg: "https://picsum.photos/250?image=13",productName: "e"),CardItem(
productImg: "https://picsum.photos/250?image=14",productName: "f"),CardItem(
productImg: "https://picsum.photos/250?image=15",productName: "g"),CardItem(
productImg: "https://picsum.photos/250?image=16",productName: "h")
];
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
actions: <Widget>[
IconButton(
icon: Icon(Icons.shopping_cart),onPressed: () {},)
],backgroundColor: Colors.green,/* drawer: Drawer(
child: AppDrawer(),*/
body: SingleChildScrollView(
child: ConstrainedBox(
constraints: BoxConstraints(),child: Column(
children: <Widget>[
Container(
height: 200,width: double.infinity,child: Text("HomeSlider()"),Padding(
padding: EdgeInsets.only(top: 14.0,left: 8.0,right: 8.0),child: Text(
'leatest_producrs',style: TextStyle(
color: Theme.of(context).accentColor,fontSize: 18,fontWeight: FontWeight.w700)),Container(
margin: EdgeInsets.symmetric(vertical: 8.0),child: ListView.builder(
shrinkWrap: true,scrollDirection: Axis.horizontal,itemCount: cards.length,itemBuilder: (BuildContext context,int index) => Card(
child: InkWell(
child: Column(
children: [
Flexible(
child: Container(
height: double.infinity,width: 120,decoration: BoxDecoration(
image: DecorationImage(
image: NetworkImage(
cards[index].productImg,fit: BoxFit.fitHeight,)),Container(
width: 150,padding: EdgeInsets.all(10),child: Text(cards[index].productName,style: new TextStyle(fontSize: 12),softWrap: true),],onTap: () {
},Container(
child: Padding(
padding: EdgeInsets.only(top: 6.0,child: Image(
fit: BoxFit.cover,image: AssetImage('assets/images/banner-1.jpg'),Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,children: <Widget>[
Padding(
padding: EdgeInsets.only(top: 8.0,child: Text('Featured Products',style: TextStyle(
color: Theme.of(context).accentColor,Padding(
padding: const EdgeInsets.only(
right: 8.0,top: 8.0,left: 8.0),child: RaisedButton(
color: Theme.of(context).primaryColor,child: Text('View All',style: TextStyle(color: Colors.white)),onPressed: () {
Navigator.pushNamed(context,'/categorise');
}),)
],Container(
child: GridView.count(
shrinkWrap: true,physics: NeverScrollableScrollPhysics(),crossAxisCount: 2,padding:
EdgeInsets.only(top: 8,left: 6,right: 6,bottom: 12),children: List.generate(cards.length,(index) {
return Container(
child: Card(
clipBehavior: Clip.antiAlias,child: InkWell(
onTap: () {
print('Card tapped.');
},child: Column(
crossAxisAlignment: CrossAxisAlignment.start,children: <Widget>[
Flexible(
child: Container(
height: double.infinity,decoration: BoxDecoration(
image: DecorationImage(
image: NetworkImage(
cards[index].productImg,ListTile(
title: Text(
cards[index].productName,style: TextStyle(
fontWeight: FontWeight.w700,fontSize: 12),);
}),Container(
child: Padding(
padding: EdgeInsets.only(
top: 6.0,right: 8.0,bottom: 10),image: AssetImage('assets/images/banner-2.jpg'),)
],)
);
}
}
扩展小部件必须是列，行或Flex的直接子代。您已将其包装在容器中。尝试交换“容器”和“扩展”窗口小部件。
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