android - 如何在flutter中访问json列表
问题描述
我正在尝试访问通过 API 发送的儿子。但是 JSON 包含一个列表。我无法访问它。请帮我。
这是我从 API 收到的 JSON。
{
"message": "success",
"events": [
{
"schools": 0,
"participants": 0,
"_id": "5ed6acc6836b3263e4f50662",
"eventid": "01",
"schoolname": "abc school",
"teacherid": "0015",
"teachername": "Malar",
"eventdate": "2000-03-05T18:30:00.000Z",
"eventname": "Science Workshop",
"eventdescription": "This is a very grand event.",
"eventtype": "science",
"eventimage": "none",
"__v": 0
},
{
"schools": 0,
"participants": 0,
"_id": "5ed6ad38836b3263e4f50665",
"eventid": "02",
"schoolname": "abc school",
"teacherid": "0016",
"teachername": "Malaring",
"eventdate": "2000-06-02T18:30:00.000Z",
"eventname": "Science Workshop",
"eventdescription": "This is a very grand event.",
"eventtype": "science",
"eventimage": "none",
"__v": 0
},
]
}
我的 PODO 课程是
// To parse this JSON data, do
//
// final allEvents = allEventsFromJson(jsonString);
import 'dart:convert';
GetAllEvents allEventsFromJson(String str) => GetAllEvents.fromJson(json.decode(str));
String allEventsToJson(GetAllEvents data) => json.encode(data.toJson());
class GetAllEvents {
GetAllEvents({
this.message,
this.events,
});
String message;
List<Event> events;
factory GetAllEvents.fromJson(Map<String, dynamic> json) => GetAllEvents(
message: json["message"],
events: List<Event>.from(json["events"].map((x) => Event.fromJson(x))),
);
Map<String, dynamic> toJson() => {
"message": message,
"events": List<dynamic>.from(events.map((x) => x.toJson())),
};
}
class Event {
Event({
this.schools,
this.participants,
this.id,
this.eventid,
this.schoolname,
this.teacherid,
this.teachername,
this.eventdate,
this.eventname,
this.eventdescription,
this.eventtype,
this.eventimage,
this.v,
});
int schools;
int participants;
String id;
String eventid;
String schoolname;
String teacherid;
String teachername;
DateTime eventdate;
String eventname;
String eventdescription;
String eventtype;
String eventimage;
int v;
factory Event.fromJson(Map<String, dynamic> json) => Event(
schools: json["schools"],
participants: json["participants"],
id: json["_id"],
eventid: json["eventid"],
schoolname: json["schoolname"],
teacherid: json["teacherid"],
teachername: json["teachername"],
eventdate: DateTime.parse(json["eventdate"]),
eventname: json["eventname"],
eventdescription: json["eventdescription"],
eventtype: json["eventtype"],
eventimage: json["eventimage"],
v: json["__v"],
);
Map<String, dynamic> toJson() => {
"schools": schools,
"participants": participants,
"_id": id,
"eventid": eventid,
"schoolname": schoolname,
"teacherid": teacherid,
"teachername": teachername,
"eventdate": eventdate.toIso8601String(),
"eventname": eventname,
"eventdescription": eventdescription,
"eventtype": eventtype,
"eventimage": eventimage,
"__v": v,
};
}
我未来的功能是:
final String getAllEventsUrl = "http://192.168.1.5:8080/api/events/getall";
Future getAllEvents() async {
Response response = await post(getAllEventsUrl);
var result = response.body;
var body = jsonDecode(result);
return GetAllEvents.fromJson(body);
}
我的代码是:
Container(
margin: EdgeInsets.fromLTRB(5, 0, 5, 0),
child: FutureBuilder(
future: eventsApi.getAllEvents(),
builder: (context, snapshot) {
if(snapshot.hasData){
print(snapshot.data);
List<GetAllEvents> events = snapshot.data;
ListView(
children: events.map((e) => ListTile(title: Text(e.events[0].eventdescription),)).toList(),
);
}
return Center(child: CircularProgressIndicator());
},
),
);
我收到这个错误
'GetAllEvents' 类型不是 'List' 类型的子类型我现在应该做什么。请帮忙。
解决方案
您可以在下面复制粘贴运行完整代码
第 1 步:您可以提供类型GetAllEvents
和Future
第AsyncSnapshot<GetAllEvents>
2 步:您需要检查connectionState
Future<GetAllEvents> _future;
...
@override
void initState() {
_future = getAllEvents();
...
Future<GetAllEvents> getAllEvents() async {
...
FutureBuilder(
future: _future,
builder: (context, AsyncSnapshot<GetAllEvents> snapshot) {
switch (snapshot.connectionState) {
...
case ConnectionState.waiting:
return Center(child: CircularProgressIndicator());
case ConnectionState.active:
return Text('');
case ConnectionState.done:
if (snapshot.hasError) {
...
} else {
return ListView.builder(
itemCount: snapshot.data.events.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(snapshot
.data.events[index].eventdescription))
工作演示
完整代码
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
GetAllEvents allEventsFromJson(String str) =>
GetAllEvents.fromJson(json.decode(str));
String allEventsToJson(GetAllEvents data) => json.encode(data.toJson());
class GetAllEvents {
GetAllEvents({
this.message,
this.events,
});
String message;
List<Event> events;
factory GetAllEvents.fromJson(Map<String, dynamic> json) => GetAllEvents(
message: json["message"],
events: List<Event>.from(json["events"].map((x) => Event.fromJson(x))),
);
Map<String, dynamic> toJson() => {
"message": message,
"events": List<dynamic>.from(events.map((x) => x.toJson())),
};
}
class Event {
Event({
this.schools,
this.participants,
this.id,
this.eventid,
this.schoolname,
this.teacherid,
this.teachername,
this.eventdate,
this.eventname,
this.eventdescription,
this.eventtype,
this.eventimage,
this.v,
});
int schools;
int participants;
String id;
String eventid;
String schoolname;
String teacherid;
String teachername;
DateTime eventdate;
String eventname;
String eventdescription;
String eventtype;
String eventimage;
int v;
factory Event.fromJson(Map<String, dynamic> json) => Event(
schools: json["schools"],
participants: json["participants"],
id: json["_id"],
eventid: json["eventid"],
schoolname: json["schoolname"],
teacherid: json["teacherid"],
teachername: json["teachername"],
eventdate: DateTime.parse(json["eventdate"]),
eventname: json["eventname"],
eventdescription: json["eventdescription"],
eventtype: json["eventtype"],
eventimage: json["eventimage"],
v: json["__v"],
);
Map<String, dynamic> toJson() => {
"schools": schools,
"participants": participants,
"_id": id,
"eventid": eventid,
"schoolname": schoolname,
"teacherid": teacherid,
"teachername": teachername,
"eventdate": eventdate.toIso8601String(),
"eventname": eventname,
"eventdescription": eventdescription,
"eventtype": eventtype,
"eventimage": eventimage,
"__v": v,
};
}
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;
Future<GetAllEvents> _future;
Future<GetAllEvents> getAllEvents() async {
String jsonString = '''
{
"message": "success",
"events": [
{
"schools": 0,
"participants": 0,
"_id": "5ed6acc6836b3263e4f50662",
"eventid": "01",
"schoolname": "abc school",
"teacherid": "0015",
"teachername": "Malar",
"eventdate": "2000-03-05T18:30:00.000Z",
"eventname": "Science Workshop",
"eventdescription": "This is a very grand event.",
"eventtype": "science",
"eventimage": "none",
"__v": 0
},
{
"schools": 0,
"participants": 0,
"_id": "5ed6ad38836b3263e4f50665",
"eventid": "02",
"schoolname": "abc school",
"teacherid": "0016",
"teachername": "Malaring",
"eventdate": "2000-06-02T18:30:00.000Z",
"eventname": "Science Workshop",
"eventdescription": "This is a very grand event.",
"eventtype": "science",
"eventimage": "none",
"__v": 0
}
]
}
''';
//Response response = await post(getAllEventsUrl);
http.Response response = http.Response(jsonString, 200);
var result = response.body;
var body = jsonDecode(result);
return GetAllEvents.fromJson(body);
}
@override
void initState() {
_future = getAllEvents();
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: FutureBuilder(
future: _future,
builder: (context, AsyncSnapshot<GetAllEvents> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text('none');
case ConnectionState.waiting:
return Center(child: CircularProgressIndicator());
case ConnectionState.active:
return Text('');
case ConnectionState.done:
if (snapshot.hasError) {
return Text(
'${snapshot.error}',
style: TextStyle(color: Colors.red),
);
} else {
return ListView.builder(
itemCount: snapshot.data.events.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(snapshot
.data.events[index].eventdescription));
});
}
}
}));
}
}
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