在具有多个列表的单个页面中显示来自 API 的嵌套 JSON
Show nested JSON from API in single Page with multiple lists
我是 Flutter 的新手,我正在努力处理来自 API 的嵌套 JSON 我想在一页中显示哪些数据。
我从 URL 得到这个 JSON 并在 class 中解码它,它工作正常:
{
"service1": [
{
"firstname": "Peter",
"lastname": "Smith"
},
{
"firstname": "Paul",
"lastname": "Johnson"
}
],
"service2": [
{
"firstname": "Mary",
"lastname": "Williams"
},
{
"firstname": "Guy",
"lastname": "Brown"
}
]
}
类:
/*------------------------------
staff.dart
------------------------------*/
import 'dart:convert';
class Staff {
String? service;
String? firstname;
String? lastname;
Staff({this.service, this.firstname, this.lastname});
factory Staff.fromMap(Map<String, dynamic> data) => Staff(
service: data['service'] as String?,
firstname: data['firstname'] as String?,
lastname: data['lastname'] as String?,
);
Map<String, dynamic> toMap() => {
'service': '',
'firstname': firstname,
'lastname': lastname,
};
/// Parses the string and returns the resulting Json object.
factory Staff.fromJson(String data) {
return Staff.fromMap(json.decode(data) as Map<String, dynamic>);
}
/// Converts [Staff] to a JSON string.
String toJson() => json.encode(toMap());
}
/*------------------------------
servicedesk.dart
------------------------------*/
import 'dart:convert';
import 'staff.dart';
class ServiceDesk {
List<Staff>? service1;
List<Staff>? service2;
ServiceDesk({
this.service1,
this.service2,
});
factory ServiceDesk.fromMap(Map<String, dynamic> data) => ServiceDesk(
service1: (data['service1'] as List<dynamic>?)
?.map((e) => Staff.fromMap(e as Map<String, dynamic>))
.toList(),
service2: (data['service2'] as List<dynamic>?)
?.map((e) => Staff.fromMap(e as Map<String, dynamic>))
.toList(),
);
Map<String, dynamic> toMap() => {
'service1': service1?.map((e) => e.toMap()).toList(),
'service2': service2?.map((e) => e.toMap()).toList(),
};
/// Parses the string and returns the resulting Json object as [ServiceDesk].
factory ServiceDesk.fromJson(String data) {
var object = ServiceDesk.fromMap(json.decode(data) as Map<String, dynamic>);
object.b1!.insert(0, Staff(service: 'Title for Service1'));
object.b2!.insert(0, Staff(service: 'Title for Service2'));
return object;
}
/// Converts to a JSON string.
String toJson() => json.encode(toMap());
}
这就是我的代码(之间的伪代码):
// PSEUDOCODE!!
Widget ListWithService(List<Staff>? entry) {
return ListView.builder(
itemCount: entry!.length,
padding: const EdgeInsets.all(2.0),
itemBuilder: (context, position) {
final item = entry[position];
if (item.service != null) {
return ListTile(
title: Text(
'${item.service}',
style: Theme.of(context).textTheme.headline5,
),
);
} else {
return ListTile(
title: Text(
'${item.firstname} ${item.lastname}',
style: Theme.of(context).textTheme.bodyText1,
),
);
}
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Service Desk'),
),
body: FutureBuilder<sdclass.ServiceDesk>(
future: getData(),
builder: (context, snapshot) {
if (snapshot.hasData == true) {
return [
ListWithService(snapshot.data.service1),
ListWithSercice(snapshot.data.service1);
] // PSEUDOCODE!!
} else if (snapshot.hasError) {
return const Icon(
Icons.error_outline,
color: Colors.red,
size: 60,
);
} else {
return const Center(
child: CircularProgressIndicator(),
);
}
}
),
);
}
最后我想要的在整页上应该是这样的:
服务标题1(标题)
彼得·史密斯
保罗·约翰逊
服务标题2(标题)
玛丽·威廉姆斯
盖伊·布朗
有人可以帮我写代码让它工作吗?
更新代码
感谢您更新示例。我在我的代码中测试了它。首先,一切看起来都很好。但是当我切换到带有 json 的屏幕时,我得到一个错误:
Expected a value of type 'FutureOr<Map<String, List<Map<String, String>>>>', but got one of type '_JsonMap'
import 'dart:convert';
import 'dart:core';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
class ServiceDesk extends StatelessWidget {
const ServiceDesk({Key? key}) : super(key: key);
Future<Map<String, List<Map<String, String>>>> getData() async {
String link = "https://url-to-json-file.json";
final res = await http
.get(Uri.parse(link), headers: {"Accept": "application/json"});
if (res.statusCode == 200) {
var utf8decoded = utf8.decode(res.body.toString().codeUnits);
var decoded = json.decode(utf8decoded);
return decoded;
} else {
throw Exception('Failed to load JSON');
}
}
Widget listViewWidget(
Iterable<MapEntry<String, List<Map<String, String>>>> entries) {
return ListView.builder(
itemCount: entries.length,
padding: const EdgeInsets.all(2.0),
itemBuilder: (context, index) {
final entry = entries.elementAt(index);
final key = entry.key;
final values = entry.value;
return Column(
children: [
ListTile(
title: Text(
'Title for $key',
style: Theme.of(context).textTheme.headline5,
),
),
for (var person in values)
ListTile(
title: Text(
'${person["firstname"]} ${person["lastname"]}',
style: Theme.of(context).textTheme.bodyText1,
),
),
],
);
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Service Desk'),
),
body: FutureBuilder(
future: getData(),
builder: (_,
AsyncSnapshot<Map<String, List<Map<String, String>>>> snapshot) {
if (snapshot.hasData == true) {
final entries = snapshot.data?.entries ?? {};
return listViewWidget(entries);
} else if (snapshot.hasError) {
return Center(
child: Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Icon(
Icons.error_outline,
color: Colors.red,
size: 60,
),
Text("Fehler: ${snapshot.error}"),
],
));
} else {
return const Center(
child: CircularProgressIndicator(),
);
}
}),
);
}
}
在Dart语言中,你可以在列表中使用for循环,这样更容易与Flutter一起工作UI。
import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'dart:convert';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const RootView(),
);
}
}
class RootView extends StatelessWidget {
const RootView({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: TextButton(
child: const Text('GO TO SAFF SERVICE'),
onPressed: () {
Navigator.push(context, Home.route());
},
),
),
);
}
}
class Home extends StatefulWidget {
const Home({Key? key}) : super(key: key);
static Route route() {
return CupertinoPageRoute(builder: (_) => const Home());
}
@override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
late Future<StaffService> staffService;
@override
void initState() {
staffService = getStaffService();
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('Services')),
body: Center(
child: FutureBuilder<StaffService>(
future: staffService,
builder: (_, snapshot) {
if (snapshot.hasData) {
final saff = snapshot.data!;
return ListView(
children: [
if (saff.service1.isNotEmpty)
StaffServiceTile(
title: Text(
'Title for Service 1',
style: Theme.of(context).textTheme.headline5,
),
services: saff.service1,
),
if (saff.service2.isNotEmpty)
StaffServiceTile(
title: Text(
'Title for Service 2',
style: Theme.of(context).textTheme.headline5,
),
services: saff.service2,
),
],
);
} else if (snapshot.hasError) {
return const Text('Error on loaad data. Try again later.');
} else {
return const CircularProgressIndicator();
}
},
),
),
);
}
}
class StaffServiceTile extends StatelessWidget {
const StaffServiceTile({
Key? key,
required this.title,
required this.services,
}) : super(key: key);
final Widget title;
final List<Service> services;
@override
Widget build(BuildContext context) {
return Column(
children: [
ListTile(title: title),
for (var person in services)
ListTile(
title: Text(
'${person.firstname} ${person.lastname}',
),
),
],
);
}
}
class StaffService {
StaffService({this.service1 = const [], this.service2 = const []});
List<Service> service1, service2;
factory StaffService.fromJson(String str) {
return StaffService.fromMap(json.decode(str));
}
String toJson() => json.encode(toMap());
factory StaffService.fromMap(Map<String, dynamic> json) => StaffService(
service1: List<Service>.from(json["service1"].map((x) => Service.fromMap(x))),
service2: List<Service>.from(json["service2"].map((x) => Service.fromMap(x))),
);
Map<String, dynamic> toMap() => {
"service1": List<dynamic>.from(service1.map((x) => x.toMap())),
"service2": List<dynamic>.from(service2.map((x) => x.toMap())),
};
}
class Service {
Service({this.firstname, this.lastname});
String? firstname, lastname;
factory Service.fromJson(String str) => Service.fromMap(json.decode(str));
String toJson() => json.encode(toMap());
factory Service.fromMap(Map<String, dynamic> json) => Service(
firstname: json["firstname"],
lastname: json["lastname"],
);
Map<String, dynamic> toMap() => {
"firstname": firstname,
"lastname": lastname,
};
}
Future<StaffService> getStaffService() async {
await Future.delayed(const Duration(seconds: 2));
return StaffService.fromMap(data); // <- use fromJson if you load data from the JSON.
}
final data = <String, List<Map<String, String>>>{
"service1": [
{"firstname": "Peter", "lastname": "Smith"},
{"firstname": "Paul", "lastname": "Johnson"}
],
"service2": [
{"firstname": "Mary", "lastname": "Williams"},
{"firstname": "Guy", "lastname": "Brown"}
]
};
复制并粘贴到 DartPad 中进行测试。
我是 Flutter 的新手,我正在努力处理来自 API 的嵌套 JSON 我想在一页中显示哪些数据。
我从 URL 得到这个 JSON 并在 class 中解码它,它工作正常:
{
"service1": [
{
"firstname": "Peter",
"lastname": "Smith"
},
{
"firstname": "Paul",
"lastname": "Johnson"
}
],
"service2": [
{
"firstname": "Mary",
"lastname": "Williams"
},
{
"firstname": "Guy",
"lastname": "Brown"
}
]
}
类:
/*------------------------------
staff.dart
------------------------------*/
import 'dart:convert';
class Staff {
String? service;
String? firstname;
String? lastname;
Staff({this.service, this.firstname, this.lastname});
factory Staff.fromMap(Map<String, dynamic> data) => Staff(
service: data['service'] as String?,
firstname: data['firstname'] as String?,
lastname: data['lastname'] as String?,
);
Map<String, dynamic> toMap() => {
'service': '',
'firstname': firstname,
'lastname': lastname,
};
/// Parses the string and returns the resulting Json object.
factory Staff.fromJson(String data) {
return Staff.fromMap(json.decode(data) as Map<String, dynamic>);
}
/// Converts [Staff] to a JSON string.
String toJson() => json.encode(toMap());
}
/*------------------------------
servicedesk.dart
------------------------------*/
import 'dart:convert';
import 'staff.dart';
class ServiceDesk {
List<Staff>? service1;
List<Staff>? service2;
ServiceDesk({
this.service1,
this.service2,
});
factory ServiceDesk.fromMap(Map<String, dynamic> data) => ServiceDesk(
service1: (data['service1'] as List<dynamic>?)
?.map((e) => Staff.fromMap(e as Map<String, dynamic>))
.toList(),
service2: (data['service2'] as List<dynamic>?)
?.map((e) => Staff.fromMap(e as Map<String, dynamic>))
.toList(),
);
Map<String, dynamic> toMap() => {
'service1': service1?.map((e) => e.toMap()).toList(),
'service2': service2?.map((e) => e.toMap()).toList(),
};
/// Parses the string and returns the resulting Json object as [ServiceDesk].
factory ServiceDesk.fromJson(String data) {
var object = ServiceDesk.fromMap(json.decode(data) as Map<String, dynamic>);
object.b1!.insert(0, Staff(service: 'Title for Service1'));
object.b2!.insert(0, Staff(service: 'Title for Service2'));
return object;
}
/// Converts to a JSON string.
String toJson() => json.encode(toMap());
}
这就是我的代码(之间的伪代码):
// PSEUDOCODE!!
Widget ListWithService(List<Staff>? entry) {
return ListView.builder(
itemCount: entry!.length,
padding: const EdgeInsets.all(2.0),
itemBuilder: (context, position) {
final item = entry[position];
if (item.service != null) {
return ListTile(
title: Text(
'${item.service}',
style: Theme.of(context).textTheme.headline5,
),
);
} else {
return ListTile(
title: Text(
'${item.firstname} ${item.lastname}',
style: Theme.of(context).textTheme.bodyText1,
),
);
}
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Service Desk'),
),
body: FutureBuilder<sdclass.ServiceDesk>(
future: getData(),
builder: (context, snapshot) {
if (snapshot.hasData == true) {
return [
ListWithService(snapshot.data.service1),
ListWithSercice(snapshot.data.service1);
] // PSEUDOCODE!!
} else if (snapshot.hasError) {
return const Icon(
Icons.error_outline,
color: Colors.red,
size: 60,
);
} else {
return const Center(
child: CircularProgressIndicator(),
);
}
}
),
);
}
最后我想要的在整页上应该是这样的:
服务标题1(标题)
彼得·史密斯
保罗·约翰逊
服务标题2(标题)
玛丽·威廉姆斯
盖伊·布朗
有人可以帮我写代码让它工作吗?
更新代码
感谢您更新示例。我在我的代码中测试了它。首先,一切看起来都很好。但是当我切换到带有 json 的屏幕时,我得到一个错误:
Expected a value of type 'FutureOr<Map<String, List<Map<String, String>>>>', but got one of type '_JsonMap'
import 'dart:convert';
import 'dart:core';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
class ServiceDesk extends StatelessWidget {
const ServiceDesk({Key? key}) : super(key: key);
Future<Map<String, List<Map<String, String>>>> getData() async {
String link = "https://url-to-json-file.json";
final res = await http
.get(Uri.parse(link), headers: {"Accept": "application/json"});
if (res.statusCode == 200) {
var utf8decoded = utf8.decode(res.body.toString().codeUnits);
var decoded = json.decode(utf8decoded);
return decoded;
} else {
throw Exception('Failed to load JSON');
}
}
Widget listViewWidget(
Iterable<MapEntry<String, List<Map<String, String>>>> entries) {
return ListView.builder(
itemCount: entries.length,
padding: const EdgeInsets.all(2.0),
itemBuilder: (context, index) {
final entry = entries.elementAt(index);
final key = entry.key;
final values = entry.value;
return Column(
children: [
ListTile(
title: Text(
'Title for $key',
style: Theme.of(context).textTheme.headline5,
),
),
for (var person in values)
ListTile(
title: Text(
'${person["firstname"]} ${person["lastname"]}',
style: Theme.of(context).textTheme.bodyText1,
),
),
],
);
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Service Desk'),
),
body: FutureBuilder(
future: getData(),
builder: (_,
AsyncSnapshot<Map<String, List<Map<String, String>>>> snapshot) {
if (snapshot.hasData == true) {
final entries = snapshot.data?.entries ?? {};
return listViewWidget(entries);
} else if (snapshot.hasError) {
return Center(
child: Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Icon(
Icons.error_outline,
color: Colors.red,
size: 60,
),
Text("Fehler: ${snapshot.error}"),
],
));
} else {
return const Center(
child: CircularProgressIndicator(),
);
}
}),
);
}
}
在Dart语言中,你可以在列表中使用for循环,这样更容易与Flutter一起工作UI。
import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'dart:convert';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const RootView(),
);
}
}
class RootView extends StatelessWidget {
const RootView({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: TextButton(
child: const Text('GO TO SAFF SERVICE'),
onPressed: () {
Navigator.push(context, Home.route());
},
),
),
);
}
}
class Home extends StatefulWidget {
const Home({Key? key}) : super(key: key);
static Route route() {
return CupertinoPageRoute(builder: (_) => const Home());
}
@override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
late Future<StaffService> staffService;
@override
void initState() {
staffService = getStaffService();
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('Services')),
body: Center(
child: FutureBuilder<StaffService>(
future: staffService,
builder: (_, snapshot) {
if (snapshot.hasData) {
final saff = snapshot.data!;
return ListView(
children: [
if (saff.service1.isNotEmpty)
StaffServiceTile(
title: Text(
'Title for Service 1',
style: Theme.of(context).textTheme.headline5,
),
services: saff.service1,
),
if (saff.service2.isNotEmpty)
StaffServiceTile(
title: Text(
'Title for Service 2',
style: Theme.of(context).textTheme.headline5,
),
services: saff.service2,
),
],
);
} else if (snapshot.hasError) {
return const Text('Error on loaad data. Try again later.');
} else {
return const CircularProgressIndicator();
}
},
),
),
);
}
}
class StaffServiceTile extends StatelessWidget {
const StaffServiceTile({
Key? key,
required this.title,
required this.services,
}) : super(key: key);
final Widget title;
final List<Service> services;
@override
Widget build(BuildContext context) {
return Column(
children: [
ListTile(title: title),
for (var person in services)
ListTile(
title: Text(
'${person.firstname} ${person.lastname}',
),
),
],
);
}
}
class StaffService {
StaffService({this.service1 = const [], this.service2 = const []});
List<Service> service1, service2;
factory StaffService.fromJson(String str) {
return StaffService.fromMap(json.decode(str));
}
String toJson() => json.encode(toMap());
factory StaffService.fromMap(Map<String, dynamic> json) => StaffService(
service1: List<Service>.from(json["service1"].map((x) => Service.fromMap(x))),
service2: List<Service>.from(json["service2"].map((x) => Service.fromMap(x))),
);
Map<String, dynamic> toMap() => {
"service1": List<dynamic>.from(service1.map((x) => x.toMap())),
"service2": List<dynamic>.from(service2.map((x) => x.toMap())),
};
}
class Service {
Service({this.firstname, this.lastname});
String? firstname, lastname;
factory Service.fromJson(String str) => Service.fromMap(json.decode(str));
String toJson() => json.encode(toMap());
factory Service.fromMap(Map<String, dynamic> json) => Service(
firstname: json["firstname"],
lastname: json["lastname"],
);
Map<String, dynamic> toMap() => {
"firstname": firstname,
"lastname": lastname,
};
}
Future<StaffService> getStaffService() async {
await Future.delayed(const Duration(seconds: 2));
return StaffService.fromMap(data); // <- use fromJson if you load data from the JSON.
}
final data = <String, List<Map<String, String>>>{
"service1": [
{"firstname": "Peter", "lastname": "Smith"},
{"firstname": "Paul", "lastname": "Johnson"}
],
"service2": [
{"firstname": "Mary", "lastname": "Williams"},
{"firstname": "Guy", "lastname": "Brown"}
]
};
复制并粘贴到 DartPad 中进行测试。