如何从颤振中的下拉列表中过滤JSON [英] how to filter json from dropdown in flutter
本文介绍了如何从颤振中的下拉列表中过滤JSON的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
以下是我的代码
数据-lang="js"数据-隐藏="假"数据-控制台="真"数据-巴贝尔="假">import 'package:flutter/material.dart';
void main() {
runApp(new MaterialApp(
title: "Para Dai",
home: new DropDown(),
));
}
class DropDown extends StatefulWidget {
DropDown() : super();
// end
final String title = "DropDown Demo";
@override
DropDownState createState() => DropDownState();
}
class Province {
int id;
String name;
Province(this.id, this.name);
static List<Province> getProvinceList() {
return <Province>[
Province(1, 'Central Java'),
Province(2, 'East kalimantan'),
Province(3, 'East java'),
Province(4, 'Bali'),
Province(5, 'Borneo'),
];
}
}
// ADD THIS
class District {
int id;
String name;
District(this.id, this.name);
static List<District> getDistrictList() {
return <District>[
District(1, 'Demak'),
District(2, 'Solo'),
District(3, 'Sidoarjo'),
District(4, 'Bandung'),
];
}
}
class DropDownState extends State<DropDown> {
String finalUrl = '';
List<Province> _provinces = Province.getProvinceList();
List<DropdownMenuItem<Province>> _dropdownMenuItems;
Province _selectedProvince;
// ADD THIS
List<District> _disctricts = District.getDistrictList();
List<DropdownMenuItem<District>> _dropdownMenuDistricts;
District _selectedDistrict;
@override
void initState() {
_dropdownMenuItems = buildDropdownMenuItems(_provinces);
_dropdownMenuDistricts = buildDropdownDistricts(_disctricts); // Add this
_selectedProvince = _dropdownMenuItems[0].value;
_selectedDistrict = _dropdownMenuDistricts[0].value; // Add this
super.initState();
}
List<DropdownMenuItem<Province>> buildDropdownMenuItems(List provinceses) {
List<DropdownMenuItem<Province>> items = List();
for (var province in provinceses) {
items.add(
DropdownMenuItem(
value: province,
child: Text(province.name),
),
);
}
return items;
}
// ADD THIS
List<DropdownMenuItem<District>> buildDropdownDistricts(
List<District> districts) {
List<DropdownMenuItem<District>> items = List();
for (var district in districts) {
items.add(
DropdownMenuItem(
value: district,
child: Text(district.name),
),
);
}
return items;
}
onChangeDropdownItem(Province newProvince) {
// Add this
final String url =
'https://onobang.com/flutter/index.php?province=${newProvince.name}&district=${_selectedDistrict.name}';
setState(() {
_selectedProvince = newProvince;
finalUrl = url; // Add this
});
}
onChangeDistrict(District newDistrict) {
// Add this
final String url =
'https://onobang.com/flutter/index.php?province=${_selectedProvince.name}&district=${newDistrict.name}';
setState(() {
_selectedDistrict = newDistrict;
finalUrl = url; // Add this
});
}
@override
Widget build(BuildContext context) {
return new MaterialApp(
debugShowCheckedModeBanner: false,
home: new Scaffold(
appBar: new AppBar(
title: new Text("DropDown Button Example"),
),
body: new Container(
margin: const EdgeInsets.all(0.0),
padding: const EdgeInsets.all(13.0),
child: new Column(
children: <Widget>[
new Container(
margin: const EdgeInsets.all(0.0),
padding: const EdgeInsets.all(13.0),
decoration: new BoxDecoration(
border: new Border.all(color: Colors.blueGrey)),
child: new Text(
"Welcome to teacher list app, please select teacher by province / district and name"),
),
new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text("Prov : "),
SizedBox(
height: 20.0,
),
DropdownButton(
value: _selectedProvince,
items: _dropdownMenuItems,
onChanged: onChangeDropdownItem,
),
SizedBox(
height: 20.0,
),
// Text('Selected: ${_selectedProvince.name}'),
// SizedBox(
// height: 20.0,
// ),
Text(" Dist : "),
SizedBox(
height: 20.0,
),
DropdownButton(
value: _selectedDistrict,
items: _dropdownMenuDistricts,
onChanged: onChangeDistrict,
),
SizedBox(
height: 20.0,
),
// Text('Selected: ${_selectedDistrict.name}'),
// SizedBox(
// height: 20.0,
// ),
// Padding(
// padding: const EdgeInsets.all(8.0),
// child: Text('$finalUrl'),
// ),
],
),
new Card(
child: new Center(
child: TextFormField(
decoration: InputDecoration(labelText: 'Teacher Name'),
))),
new FlatButton(
color: Colors.blue,
textColor: Colors.white,
disabledColor: Colors.grey,
disabledTextColor: Colors.black,
padding: EdgeInsets.all(8.0),
splashColor: Colors.blueAccent,
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => SecondWidget(value:"$finalUrl"))
);
// what action to show next screen
},
child: Text(
"Show List",
),
),
],
),
),
),
);
}
}
// ignore: must_be_immutable
class SecondWidget extends StatelessWidget
{
String value;
SecondWidget({Key key, @required this.value}):super(key:key);
@override
Widget build(BuildContext context) {
// TODO: implement build
return Scaffold(
appBar: AppBar(title: Text("Page 2"),),
body: Column(children: <Widget>[
Text("I wish Show JSON Mysql listview with this URL : "+this.value),
RaisedButton(child: Text("Go Back"),
onPressed: () {
Navigator.pop(context);
}),
],)
);
}
}在我还是一个扑翼初学者，学扑翼非常困难之前，非常感谢你的帮助
推荐答案
编辑
如果您是指单击菜单项并更改_BuildSearchResults内容，
Your_BuildSearchResults基于LIST_SearchResult，像在onSearchTextChanged中所做的那样修改内容将起作用。在RaisedButton中，您可以使用onPressed
执行此操作
RaisedButton(
填充：const EdgeInsets.all(8.0)，
文本颜色：颜色。白色，
颜色：颜色。蓝色，
按下：(新区){
SetState((){
_myRegion=newRegion；
_earchResult.lear()；
//重新创建您的_earchResult。
})；
},
子：新文本("提交")，
)
onChanged: (newDistrict) {
setState(() {
_myDistrict = newDistrict;
_searchResult.clear();
//recreate your _searchResult again.
});
},
如果我理解清楚，您正试图通过JSON字符串GET从API创建Dropdown MenuItem。
来自不同接口的JSON，您可以加入
List<Map> _jsonApi1 = [
{"id": 0, "name": "default 1"}
];
List<Map> _jsonApi2 = [
{"id": 1, "name": "second 2"},
{"id": 2, "name": "third 3"}
];
List<Map> _myJson = new List.from(_jsonApi1)..addAll(_jsonApi2);
生成菜单项
new DropdownButton<String>(
isDense: true,
hint: new Text("${_jsonApi1[0]["name"]}"),
value: _mySelection,
onChanged: (String newValue) {
setState(() {
_mySelection = newValue;
});
print(_mySelection);
},
items: _myJson.map((Map map) {
return new DropdownMenuItem<String>(
value: map["id"].toString(),
child: new Text(
map["name"],
),
);
}).toList(),
完整代码
import 'package:flutter/material.dart';
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(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.
// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
List<Map> _jsonApi1 = [
{"id": 0, "name": "default 1"}
];
List<Map> _jsonApi2 = [
{"id": 1, "name": "second 2"},
{"id": 2, "name": "third 3"}
];
List<Map> _myJson = new List.from(_jsonApi1)..addAll(_jsonApi2);
class _MyHomePageState extends State<MyHomePage> {
String _mySelection;
@override
Widget build(BuildContext context) {
return new Scaffold(
body: SafeArea(
child: Column(
children: <Widget>[
Container(
height: 500.0,
child: new Center(
child: new DropdownButton<String>(
isDense: true,
hint: new Text("${_jsonApi1[0]["name"]}"),
value: _mySelection,
onChanged: (String newValue) {
setState(() {
_mySelection = newValue;
});
print(_mySelection);
},
items: _myJson.map((Map map) {
return new DropdownMenuItem<String>(
value: map["id"].toString(),
child: new Text(
map["name"],
),
);
}).toList(),
),
),
),
],
),
),
);
}
}
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