Android 如何使用flatter访问JSON对象?
如何访问JSON对象 获取Android 如何使用flatter访问JSON对象?,android,ios,json,flutter,dart,Android,Ios,Json,Flutter,Dart,如何访问JSON对象 获取Employee Title=null如何直接使用该对象 像这样获得正确的输出Text('Employee Title=${list[0].Title}')还是直接使用模型对象的任何其他方式 正确的方法是什么 import 'dart:convert'; import 'package:flutter/material.dart'; import 'package:http/http.dart' as http; import 'package:flutter/cupe
Employee Title=null
如何直接使用该对象
像这样获得正确的输出Text('Employee Title=${list[0].Title}')
还是直接使用模型对象的任何其他方式
正确的方法是什么
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:flutter/cupertino.dart';
class EmployeeModel {
int userId;
int id;
String title;
String body;
EmployeeModel({this.userId, this.id, this.title, this.body});
EmployeeModel.fromJson(Map<String, dynamic> json) {
userId = json['userId'];
id = json['id'];
title = json['title'];
body = json['body'];
}
}
class EmployeePage extends StatefulWidget {
@override
State<StatefulWidget> createState() {
// TODO: implement createState
return EmployeePageState();
}
}
class EmployeePageState extends State<EmployeePage> {
EmployeeModel model = EmployeeModel();
List<EmployeeModel> list = List();
var isLoading = false;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Employee Title = ${model.title}'),
),
body: isLoading
? Center(
child: CircularProgressIndicator(),
):Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
])));
}
@override
void initState() {
super.initState();
getEmployee(2);
}
getEmployee(int id) async {
setState(() {
isLoading = true;
});
final response =
await http.get("https://jsonplaceholder.typicode.com/posts?userId=$id");
if (response.statusCode == 200) {
list = (json.decode(response.body) as List)
.map((data) => new EmployeeModel.fromJson(data))
.toList();
setState(() {
isLoading = false;
});
}
}
}
导入'dart:convert';
进口“包装:颤振/材料.省道”;
将“package:http/http.dart”导入为http;
进口“包装:颤振/cupertino.dart”;
类雇员模型{
int用户标识;
int-id;
字符串标题;
弦体;
EmployeeModel({this.userId,this.id,this.title,this.body});
EmployeeModel.fromJson(映射json){
userId=json['userId'];
id=json['id'];
title=json['title'];
body=json['body'];
}
}
类EmployeePage扩展StatefulWidget{
@凌驾
状态createState(){
//TODO:实现createState
返回EmployeePageState();
}
}
类EmployeePageState扩展了状态{
EmployeeModel=EmployeeModel();
List=List();
var isLoading=false;
@凌驾
小部件构建(构建上下文){
返回脚手架(
appBar:appBar(
title:Text('Employee title=${model.title}'),
),
主体:卸载
?中心(
子对象:CircularProgressIndicator(),
):中心(
子:列(
mainAxisAlignment:mainAxisAlignment.center,
儿童:[
])));
}
@凌驾
void initState(){
super.initState();
一名雇员(2名);
}
getEmployee(int-id)异步{
设置状态(){
isLoading=true;
});
最后答复=
等待http.get(“https://jsonplaceholder.typicode.com/posts?userId=$id”);
如果(response.statusCode==200){
list=(json.decode(response.body)作为列表)
.map((数据)=>newEmployeeModel.fromJson(数据))
.toList();
设置状态(){
isLoading=false;
});
}
}
}
我的代码运行良好,但我想知道这是正确的方法吗?
这边Text('Employee Title=${list[0].Title}')
或者,如果我想直接使用对象,该怎么办
我的代码运行良好,但我想知道这是正确的方法吗?
这边Text('Employee Title=${list[0].Title}')
或者,如果我想直接使用object,方法是什么?您从未从json初始化模型,因此模型的所有属性都为空。试着这样做:
if (response.statusCode == 200) {
final employees = json.decode(response.body);
list = (employees as List)
.map((data) => new EmployeeModel.fromJson(data))
.toList();
setState(() {
model = new EmployeeModel.fromJson(employees[0]);
isLoading = false;
});
}
我有两个模型课:
class EmployeeList {
final List<Employee> employees;
EmplyeeList({
this.employees,
});
factory EmployeeList.fromJson(List<dynamic> parsedJson) {
List<Employee> employees = new List<Employee>();
employees = parsedJson.map((i)=>Employee.fromJson(i)).toList();
return new EmployeeList(
employees: employees
);
}
}
class Employee{
final String id;
final String title;
final String body;
final String userId;
Employee({
String userId;
String id;
String title;
String body;
}) ;
factory Employee.fromJson(Map<String, dynamic> json){
return new Employee(
id: json['id'],
userId:[userId]
title: json['title'],
body: json['body'],
);
}
}
class员工列表{
最终员工名单;
雇主({
这是我的员工,
});
FactoryEmployeeList.fromJson(List parsedJson){
列出员工=新列表();
employees=parsedJson.map((i)=>Employee.fromJson(i)).toList();
返回新员工列表(
雇员:雇员
);
}
}
班级员工{
最终字符串id;
最后的字符串标题;
最终管柱体;
最终字符串用户标识;
雇员({
字符串用户标识;
字符串id;
字符串标题;
弦体;
}) ;
factory Employee.fromJson(映射json){
返回新员工(
id:json['id'],
userId:[用户id]
标题:json['title'],
body:json['body'],
);
}
}
也许还可以考虑使用FutureBuilder…从Flatter文档:试试这个
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: EmployeePage(),
);
}
}
class EmployeePage extends StatefulWidget {
@override
State<StatefulWidget> createState() => EmployeePageState();
}
class EmployeePageState extends State<EmployeePage> {
Future<List<EmployeeModel>> _employeeList;
@override
void initState() {
_employeeList = _getEmployee(2);
super.initState();
}
Future<List<EmployeeModel>> _getEmployee(int id) async {
final response = await http.get(
"https://jsonplaceholder.typicode.com/posts?userId=$id",
);
if (response.statusCode == 200) {
final jsonBody = json.decode(response.body) as List;
return jsonBody.map((data) => new EmployeeModel.fromJson(data)).toList();
} else
throw Exception("Unable to get Employee list");
}
@override
Widget build(BuildContext context) {
return FutureBuilder<List<EmployeeModel>>(
future: _employeeList,
builder: (context, snapshot) {
print(snapshot);
if (snapshot.hasData)
return _buildBody(snapshot.data);
else if (snapshot.hasError)
return _buildErrorPage(snapshot.error);
else
return _buildLoadingPage();
},
);
}
Widget _buildBody(List<EmployeeModel> employeeList) => Scaffold(
appBar: AppBar(
title: Text('Employee Title = ${employeeList[0].title}'),
),
body: ListView.builder(
itemCount: employeeList.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(employeeList[index].title),
);
},
),
);
Widget _buildErrorPage(error) => Material(
child: Center(
child: Text("ERROR: $error"),
),
);
Widget _buildLoadingPage() => Material(
child: Center(
child: CircularProgressIndicator(),
),
);
}
class EmployeeModel {
int userId;
int id;
String title;
String body;
EmployeeModel({this.userId, this.id, this.title, this.body});
EmployeeModel.fromJson(Map<String, dynamic> json) {
userId = json['userId'];
id = json['id'];
title = json['title'];
body = json['body'];
}
}
导入'dart:convert';
进口“包装:颤振/材料.省道”;
将“package:http/http.dart”导入为http;
void main()=>runApp(MyApp());
类MyApp扩展了无状态小部件{
@凌驾
小部件构建(构建上下文){
返回材料PP(
主页:EmployeePage(),
);
}
}
类EmployeePage扩展StatefulWidget{
@凌驾
State createState()=>EmployeePageState();
}
类EmployeePageState扩展了状态{
未来雇员名单;
@凌驾
void initState(){
_employeeList=\u getEmployee(2);
super.initState();
}
Future\u getEmployee(int-id)异步{
最终响应=等待http.get(
"https://jsonplaceholder.typicode.com/posts?userId=$id“,
);
如果(response.statusCode==200){
final jsonBody=json.decode(response.body)作为列表;
返回jsonBody.map((数据)=>newEmployeeModel.fromJson(数据)).toList();
}否则
抛出异常(“无法获取员工列表”);
}
@凌驾
小部件构建(构建上下文){
回归未来建设者(
未来:_员工名单,
生成器:(上下文,快照){
打印(快照);
if(snapshot.hasData)
返回构建体(snapshot.data);
else if(snapshot.hasrerror)
返回_buildErrorPage(snapshot.error);
其他的
返回_buildLoadingPage();
},
);
}
Widget\u buildBody(List employeeList)=>Scaffold(
appBar:appBar(
title:Text('Employee title=${employeeList[0].title}'),
),
正文:ListView.builder(
itemCount:employeeList.length,
itemBuilder:(上下文,索引){
返回列表块(
标题:文本(员工列表[索引].标题),
);
},
),
);
小部件构建错误页面(错误)=>材料(
儿童:中心(
子项:文本(“错误:$ERROR”),
),
);
小部件_buildLoadingPage()=>材质(
儿童:中心(
子对象:CircularProgressIndicator(),
),
);
}
类雇员模型{
int用户标识;
int-id;
字符串标题;
弦体;
EmployeeModel({this.userId,this.id,this.title,this.body});
EmployeeModel.fromJson(映射json){
userId=json['userId'];
id=json['id'];
title=json['title'];
body=json['body'];
}
}