[英]Why my list is not updating while using setState in Flutter
我在我的文件中制作了一个OriginDestination
类的列表,即_allCities
。 然后我分配了所有值filteredCities
和cities
在initState
。
然后我做了一个函数 runFilter ,它会从 TextField 中获取关键字并相应地过滤结果并将它们保存到resultCities
。 然后我使用resultCities
在ListView.builder
显示信息。 但问题是,该列表没有根据我正在搜索的关键字进行过滤。
此外,如果您能提出更好的使用参数城市的方法,我将不胜感激,即我不认为将cities
作为参数通过状态的构造函数传递是一种很好的做法。
这是代码 -
import 'package:flutter/material.dart';
import 'package:passenger_flutter_app/models/new_city.dart';
import 'package:passenger_flutter_app/models/origin_destination.dart';
import 'package:passenger_flutter_app/utils/colors.dart';
class SelectionScreen extends StatefulWidget {
List<OriginDestination>? cities;
SelectionScreen({this.cities});
@override
_SelectionScreenState createState() => _SelectionScreenState(cities);
}
class _SelectionScreenState extends State<SelectionScreen> {
final List<OriginDestination>? _allCities;
_SelectionScreenState(this._allCities);
bool originSelected=false;
List<OriginDestination>? resultCities = [];
List<OriginDestination>? filteredCities = [];
void getCitiesFromResponse() {
/*for(var city in _allCities!) {
cities!.add(city.origin!);
}*/
filteredCities=_allCities;
resultCities=_allCities;
}
@override
initState() {
// at the beginning, all users are shown
getCitiesFromResponse();
super.initState();
}
void _runFilter(String enteredKeyword) {
if (enteredKeyword.isEmpty) {
// if the search field is empty or only contains white-space, we'll display all users
filteredCities = _allCities;
} else {
filteredCities = _allCities!
.where((city) =>
city.origin!.name!.toLowerCase().contains(enteredKeyword.toLowerCase()))
.toList();
// we use the toLowerCase() method to make it case-insensitive
}
@override
void setState() {
resultCities=filteredCities;
}
}
@override
Widget build(BuildContext context) {
var originSelected;
return SafeArea(
child: Scaffold(
backgroundColor: const Color(0xffEEEDEF),
body: Column(
children: [
Padding(
padding: const EdgeInsets.symmetric(vertical: 10.0),
child: Column(
children: [
Container(
width: MediaQuery.of(context).size.width*0.8,
),
Row(
children: [
IconButton(
icon: const Icon(Icons.arrow_back),
color: Colors.orange,
onPressed: () {
Navigator.pop(context);
},
),
Column(
children: [
originSelected==true ? Container(
child: Text(''),
) :
Container(
width: MediaQuery.of(context).size.width * 0.85,
height: 50.0,
decoration: BoxDecoration(
color: Colors.white,
borderRadius:
const BorderRadius.all(Radius.circular(5.0)),
border: Border.all(color: colorAccent)),
child: TextField(
decoration: InputDecoration(
hintText: "Enter Origin",
border: InputBorder.none,
contentPadding: const EdgeInsets.only(left: 10.0),
hintStyle: TextStyle(
fontSize: 15.0,
color: Colors.grey[500],
),
),
onChanged: (value) {
_runFilter(value);
},
),
),
],
),
],
),
],
),
),
Align(
alignment: Alignment.centerLeft,
child: Padding(
padding: EdgeInsets.only(
left: MediaQuery.of(context).size.width * 0.04, top: 3.0),
child: Text(
'Popular Searches:',
style: TextStyle(
color: popUpLightTextColor,
fontSize: MediaQuery.of(context).size.width * 0.035),
),
),
),
Expanded(
child: ListView.builder(
itemCount: resultCities!.length,
itemBuilder: (context, index) {
return Padding(
padding: EdgeInsets.only(
left: 18.0, top: index==0 ? 29.0 : 15.0, bottom: 15.0),
child: InkWell(
onTap: () {
print(resultCities?[index].origin!.name);
/*setState(() {
widget.city=filteredCities[index]['city'];
print("Changed to - ");
//print(widget.city);
Navigator.pop(context);
});*/
},
child: Text(
resultCities?[index].origin!.name??"No name",
style: const TextStyle(
color: darkText,
fontSize: 15.0,
fontWeight: FontWeight.normal,
),
),
),
);
},
),
),
],
),
),
);
}
}
好像你定义了 setState 函数而不是调用它,所以而不是:
@override
void setState() {
resultCities=filteredCities;
}
写:
setState(() {
resultCities=filteredCities;
});
为什么要覆盖 setState。 您还可以将回调作为 setState 中的参数传回。
您应该在触发器上调用 setState,例如手势或按钮:
setState(() => resultCities = filteredCities);
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