Flutter 颤振:显示单个列表值时出错
在flatter中,我从磁盘读取一个文件,并将列表项显示为一个列表。使用ListView.builder可以很好地工作,但如果文本小部件显示单个值,则会出现此错误。有人能帮忙吗 我得到的错误是生成MyHomePagedirty时引发的以下范围错误,状态:_MyHomePageState9932: RangeError索引:无效值:有效值范围为空:9Flutter 颤振:显示单个列表值时出错,flutter,listview,dart,text,Flutter,Listview,Dart,Text,在flatter中,我从磁盘读取一个文件,并将列表项显示为一个列表。使用ListView.builder可以很好地工作,但如果文本小部件显示单个值,则会出现此错误。有人能帮忙吗 我得到的错误是生成MyHomePagedirty时引发的以下范围错误,状态:_MyHomePageState9932: RangeError索引:无效值:有效值范围为空:9 import 'package:flutter/material.dart'; import 'dart:convert'; import
import 'package:flutter/material.dart';
import 'dart:convert';
import 'package:flutter/services.dart';
import 'dart:async';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
//This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(),
);
}
}
______________________________
WITH List.View.builder
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
List<String> _names = [];
Future<List<String>> loadNames() async {
List<String> names = [];
await rootBundle.loadString('assets/Stulkur_A.txt').then((q) => {
for (String i in LineSplitter().convert(q)) {names.add(i)}
});
return names;
}
_setup() async {
List<String> names = await loadNames();
setState(() {
_names = names;
});
}
@override
void initState() {
_setup();
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Names'),
),
body: Center(
child: Container(
padding: EdgeInsets.all(15),
child: ListView.builder(
itemCount: _names.length,
itemBuilder: (context, index) {
return Text(_names[index]);
})),
),
);
}
}
_____________________
WITH Text widget
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
List<String> _names = [];
Future<List<String>> loadNames() async {
List<String> names = [];
await rootBundle.loadString('assets/Stulkur_A.txt').then((q) => {
for (String i in LineSplitter().convert(q)) {names.add(i)}
});
return names;
}
_setup() async {
List<String> names = await loadNames();
setState(() {
_names = names;
});
}
@override
void initState() {
_setup();
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Names'),
),
body: Center(
child: Container(
padding: EdgeInsets.all(15),
child: Text(_names[9]),
),
),
);
}
}
您应该检查_names.length==0是否显示加载程序或您想要的所有内容,否则显示ListView小部件。试试看
body: Center(
child: Container(
padding: EdgeInsets.all(15),
child: _names.isEmpty
? CircularProgressIndicator()
: ListView.builder(
itemCount: _names.length,
itemBuilder: (context, index) {
return Text(_names[index]);
},
),
),
),
重新启动你的应用程序,重新调试,并为我们提供真正的代码