RangeError(索引):无效值:有效值范围为空:0 [英] RangeError (index): Invalid value: Valid value range is empty: 0
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问题描述
我正在尝试从API获取一个列表，该列表是两个方法fetchImages和fetchCategories.第一次显示红色屏幕错误，然后2秒钟后自动加载列表.您能告诉我我的代码有什么问题，以及如何避免在我的应用程序中显示红屏错误吗?
I am trying to fetch a list from API that is two methods fetchImages and fetchCategories. the first time it is showing a red screen error and then after 2 seconds automatically it is loading the list. Can you please tell me what's the issue with my code and how to avoid showing that red screen error in my app?
Widget build(context) {
try{
if (isFirst == true) {
fetchImage();
fetchCategories(context);
isFirst = false;
}
}catch(Exception){
}
return MaterialApp(
home: Scaffold(
backgroundColor: Colors.black,
appBar: AppBar(
title: Text('Lets see images!'),
),
body: new Column(
children: <Widget>[
new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new InkResponse(
child: new Column(
children: <Widget>[
Padding(
padding: EdgeInsets.all(10.0),
child: new Image.asset(
catimages[0],
width: 60.0,
height: 60.0,
),
),
new Text(
categoriesText[0],
style: TextStyle(color: Colors.white),
),
],
),
onTap: () {
debugPrint("on tv clikced");
widget.fetchApI.fetchSubCategories(context, 6);
}),
new InkResponse(
child: new Column(
children: <Widget>[
Padding(
padding: EdgeInsets.all(10.0),
child: new Image.asset(
catimages[1],
width: 60.0,
height: 60.0,
),
),
new Text(
categoriesText[1],
style: TextStyle(color: Colors.white),
),
],
),
onTap: () {
debugPrint("on moview clicked");
widget. fetchApI.fetchSubCategories(context, 7);
},
),
new InkResponse(
child: new Column(
children: <Widget>[
Padding(
padding: EdgeInsets.all(10.0),
child: new Image.asset(
catimages[2],
width: 60.0,
height: 60.0,
),
),
new Text(
categoriesText[2],
style: TextStyle(color: Colors.white),
),
],
),
onTap: () {
debugPrint("on news clicked");
widget.fetchApI.fetchSubCategories(context, 10);
},
),
new InkResponse(
child: new Column(
children: <Widget>[
Padding(
padding: EdgeInsets.all(10.0),
child: new Image.asset(catimages[3],
width: 60.0, height: 60.0),
),
new Text(
categoriesText[3],
style: TextStyle(color: Colors.white),
),
],
),
onTap: () {
debugPrint('on shows clicked');
widget.fetchApI.fetchSubCategories(context, 8);
},
),
new InkResponse(
child: new Column(
children: <Widget>[
Padding(
padding: EdgeInsets.all(10.0),
child: new Image.asset('assets/live_icon.png',
width: 60.0, height: 60.0),
),
new Text(
'Live',
style: TextStyle(color: Colors.white),
),
],
),
onTap: () {
debugPrint('on live clicked');
},
),
],
),
ImageList(images,widget.fetchApI),
],
),
),
);
}
推荐答案
请确保指定数据列表的长度.例如，如果您使用的是 ListView.builder ，请为属性 itemCount 赋予适当的值.
Make sure specifying the length of the list of data. For example, if you're using ListView.builder give proper value to the attribute itemCount.
ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (ctx, index) {
return WidgetItem();
});
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