Flutter 我在生成过程中调用了错误setState()或markNeedsBuild()
在将图像加载到我的应用程序之前,我试图显示微光效果,但在生成过程中收到一个错误,称为Flutter 我在生成过程中调用了错误setState()或markNeedsBuild(),flutter,setstate,Flutter,Setstate,在将图像加载到我的应用程序之前,我试图显示微光效果,但在生成过程中收到一个错误,称为setState()或markNeedsBuild()。 ...some code here... child: Card( elevation: 5, child: ListView.builder( shrinkWrap: true, scrollDirection: Axis.horizontal,
setState()或markNeedsBuild()。
...some code here...
child: Card(
elevation: 5,
child: ListView.builder(
shrinkWrap: true,
scrollDirection: Axis.horizontal,
physics: ScrollPhysics(),
itemCount: widget.images.length,
itemBuilder: (context, index) {
var _image=widget.images[index];
bool showImage=true;
//todo check setState error
NetworkImage(_image).resolve(ImageConfiguration()).addListener(
ImageStreamListener(
(info, call) {
if(mounted) {
setState(() {
showImage = true;
});
}
// do something
},
),
);
return showImage?Container(
width: screenWidth(context)*0.4,
height:screenHeight(context)*0.2,
child: Image.network(
widget.images[index],
width: MediaQuery.of(context).size.width*0.5,
fit: BoxFit.cover,
),
)
:Container(
width: screenWidth(context)*0.4,
height:screenHeight(context)*0.2,
child: Shimmer.fromColors(
...some code here...
我意识到这个代码是罪犯后,评论出来,但我真的想保留它的微光效果
NetworkImage(_image).resolve(ImageConfiguration()).addListener(
ImageStreamListener(
(info, call) {
if(mounted) {
setState(() {
showImage = true;
});
}
// do something
},
),
);
我怎样才能避开它呢?这是因为在构建过程运行时,您正在尝试设置状态。您的侦听器在构建阶段被激发。 尝试使用addPostFrameCallback:
ImageStreamListener(
(info, call) {
if(mounted) {
WidgetsBinding.instance.addPostFrameCallback((_){
setState(() {
showImage = true;
});
});
}
},
true
),
您可以复制粘贴运行下面的完整代码
您可以使用软件包
并将
微光
放入占位符
CachedNetworkImage(
imageUrl: "http://via.placeholder.com/350x150",
placeholder: (context, url) => Shimmer.fromColors(
baseColor: Colors.red,
highlightColor: Colors.yellow,
child: Text(
'Shimmer',
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 40.0,
fontWeight:
FontWeight.bold,
),
),
),
errorWidget: (context, url, error) => Icon(Icons.error),
),
工作演示
完整代码
import 'package:cached_network_image/cached_network_image.dart';
import 'package:flutter/material.dart';
import 'package:shimmer/shimmer.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 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++;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
CachedNetworkImage(
imageUrl: "http://via.placeholder.com/350x150",
placeholder: (context, url) => Shimmer.fromColors(
baseColor: Colors.red,
highlightColor: Colors.yellow,
child: Text(
'Shimmer',
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 40.0,
fontWeight:
FontWeight.bold,
),
),
),
errorWidget: (context, url, error) => Icon(Icons.error),
),
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
import'package:cached_network_image/cached_network_image.dart';
进口“包装:颤振/材料.省道”;
进口“包装:微光/微光.省道”;
void main(){
runApp(MyApp());
}
类MyApp扩展了无状态小部件{
@凌驾
小部件构建(构建上下文){
返回材料PP(
标题:“颤振演示”,
主题:主题资料(
主样本:颜色。蓝色,
视觉密度:视觉密度。自适应平台密度,
),
主页:MyHomePage(标题:“颤振演示主页”),
);
}
}
类MyHomePage扩展StatefulWidget{
MyHomePage({Key,this.title}):超级(Key:Key);
最后的字符串标题;
@凌驾
_MyHomePageState createState()=>\u MyHomePageState();
}
类_MyHomePageState扩展状态{
int _计数器=0;
void _incrementCounter(){
设置状态((){
_计数器++;
});
}
@凌驾
小部件生成(BuildContext上下文){
返回脚手架(
appBar:appBar(
标题:文本(widget.title),
),
正文:中心(
子栏(
mainAxisAlignment:mainAxisAlignment.center,
儿童:[
CachedNetworkImage(
图像URL:“http://via.placeholder.com/350x150",
占位符:(上下文,url)=>Shimmer.fromColor(
基本颜色:颜色。红色,
highlightColor:Colors.yellow,
子:文本(
"微光",,
textAlign:textAlign.center,
样式:TextStyle(
字体大小:40.0,
容重:
FontWeight.bold,
),
),
),
errorWidget:(上下文、url、错误)=>图标(Icons.error),
),
正文(
“您已经按了这么多次按钮:”,
),
正文(
“$”计数器“,
风格:Theme.of(context).textTheme.headline4,
),
],
),
),
浮动操作按钮:浮动操作按钮(
按下时:\ u递增计数器,
工具提示:“增量”,
子:图标(Icons.add),
),
);
}
}
似乎ImageStreamListener只接受一个参数。我收到一个错误,对不起,我的错。我正在更新答案。谢谢,这就是我想要的。