Flutter 处理Json错误为*type';列表<;动态>';不是类型为';字符串'*
这是我的回答 我正在显示api中的列表,我得到了响应。身体完美,但不知道发生了什么 我的PODO或模型是Flutter 处理Json错误为*type';列表<;动态>';不是类型为';字符串'*,flutter,Flutter,这是我的回答 我正在显示api中的列表,我得到了响应。身体完美,但不知道发生了什么 我的PODO或模型是 class NewData { String id; String employeeName; String employeeSalary; String employeeAge; String profileImage; NewData( {this.id, this.employeeName, this.employ
class NewData {
String id;
String employeeName;
String employeeSalary;
String employeeAge;
String profileImage;
NewData(
{this.id,
this.employeeName,
this.employeeSalary,
this.employeeAge,
this.profileImage});
factory NewData.fromJson(Map<String, dynamic> json) => NewData(
id: json["id"],
employeeName: json["employee_name"],
employeeSalary: json["employee_salary"],
employeeAge: json["employee_age"],
profileImage: json["profile_image"],
);
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['id'] = this.id;
data['employee_name'] = this.employeeName;
data['employee_salary'] = this.employeeSalary;
data['employee_age'] = this.employeeAge;
data['profile_image'] = this.profileImage;
return data;
}
}
class新数据{
字符串id;
字符串employeeName;
字符串员工工资;
字符串雇员;
字符串轮廓图像;
新数据(
{this.id,
这是我的名字,
这是雇员的工资,
这就是就业年龄,
这个.profileImage});
工厂NewData.fromJson(映射json)=>NewData(
id:json[“id”],
employeeName:json[“员工姓名”],
employeeSalary:json[“员工工资”],
employeeAge:json[“雇员年龄”],
profileImage:json[“profile_image”],
);
映射到JSON(){
最终地图数据=新地图();
数据['id']=this.id;
数据['employee_name']=this.employeeName;
数据['employee_salary']=this.employeeSalary;
数据['employee_age']=此.employeeAge;
数据['profile_image']=this.profileImage;
返回数据;
}
}
我的主要任务是
body: Container(
child: Column(
children: <Widget>[
FutureBuilder<NewData>(
future: fetchPost(),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
return Text("ERROR : - " + snapshot.error.toString());
}
List<NewData> data = snapshot.data as List<NewData>;
return new ListView.builder(
itemCount: data.length,
itemBuilder: (context, index) {
return new ListTile(
title: new Text(data[index].employeeName),
);
},
);
} else {
// By default, show a loading spinner.
return Center(
child: CircularProgressIndicator(),
);
}
}),
],
),
),
);
}
Future<NewData> fetchPost() async {
var response = await http.get(url);
if (response.statusCode == 200) {
// If server returns an OK response, parse the JSON.
var resp = json.decode(response.body);
print(resp.toString());
return NewData.fromJson(resp);
} else {
// If that response was not OK, throw an error.
throw Exception('Failed to load post');
}
}
主体:容器(
子:列(
儿童:[
未来建设者(
future:fetchPost(),
生成器:(上下文,快照){
if(snapshot.connectionState==connectionState.done){
if(snapshot.hasError){
返回文本(“ERROR:-”+snapshot.ERROR.toString());
}
列表数据=快照。数据作为列表;
返回新的ListView.builder(
itemCount:data.length,
itemBuilder:(上下文,索引){
返回新的ListTile(
标题:新文本(数据[索引].employeeName),
);
},
);
}否则{
//默认情况下,显示加载微调器。
返回中心(
子对象:CircularProgressIndicator(),
);
}
}),
],
),
),
);
}
Future fetchPost()异步{
var response=wait http.get(url);
如果(response.statusCode==200){
//如果服务器返回OK响应,则解析JSON。
var resp=json.decode(response.body);
打印(分别为toString());
返回NewData.fromJson(resp);
}否则{
//如果该响应不正常,则抛出一个错误。
抛出异常(“加载post失败”);
}
}
但我犯了这个错误
类型“List”不是类型“String”的子类型
帮我做这个
我如何摆脱它?您请求的JSON将返回一个对象列表,在您的代码中,您将对单个对象进行反编码。因此,当您使用
NewData.fromJson(resp)
解析它时,您正在尝试解析对象列表,而不是单个对象
你最好做:
Iterable l = json.decode(rseponse.body);
List<NewData> dataList = l.map((Map model)=> NewData.fromJson(model)).toList();
Iterable l=json.decode(rsepose.body);
List dataList=l.map((map model)=>NewData.fromJson(model)).toList();
资料来源:
然后,您将能够将
fetchPost()
返回类型更新为Future
您请求的JSON将返回一个对象列表,并且在您的代码中取消对单个对象的编码。因此,当您使用NewData.fromJson(resp)
解析它时,您正在尝试解析对象列表,而不是单个对象
你最好做:
Iterable l = json.decode(rseponse.body);
List<NewData> dataList = l.map((Map model)=> NewData.fromJson(model)).toList();
Iterable l=json.decode(rsepose.body);
List dataList=l.map((map model)=>NewData.fromJson(model)).toList();
资料来源:
然后,您将能够将
fetchPost()
返回类型更新为Future
,您需要进行一些更改以使其正常工作:
FutureBuilder(
至FutureBuilder(
List data=snapshot.data as List;
toList data=snapshot.data;
返回新的ListView.builder(
到返回新的扩展(子项:ListView.builder(
fetchPost()方法
import 'package:http/http.dart' as http;
import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:convert';
class Demo extends StatefulWidget {
@override
_DemoState createState() => _DemoState();
}
class _DemoState extends State<Demo> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("DEMO"),
),
body: Container(
child: Column(
children: <Widget>[
FutureBuilder<List<NewData>>(
future: fetchPost(),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
return Text("ERROR : - " + snapshot.error.toString());
}
List<NewData> data = snapshot.data;
return new Expanded(
child: ListView.builder(
itemCount: data.length,
itemBuilder: (context, index) {
return new ListTile(
title: new Text(data[index].employeeName),
);
},
));
} else {
// By default, show a loading spinner.
return Center(
child: CircularProgressIndicator(),
);
}
}),
],
),
),
);
}
Future<List<NewData>> fetchPost() async {
var response =
await http.get("http://dummy.restapiexample.com/api/v1/employees");
if (response.statusCode == 200) {
// If server returns an OK response, parse the JSON.
var resp = json.decode(response.body);
print(resp.toString());
final parsed = resp.cast<Map<String, dynamic>>(); // added this
return parsed
.map<NewData>((json) => NewData.fromJson(json))
.toList(); // add this too
} else {
// If that response was not OK, throw an error.
throw Exception('Failed to load post');
}
}
}
class NewData {
String id;
String employeeName;
String employeeSalary;
String employeeAge;
String profileImage;
NewData(
{this.id,
this.employeeName,
this.employeeSalary,
this.employeeAge,
this.profileImage});
factory NewData.fromJson(Map<String, dynamic> json) => NewData(
id: json["id"],
employeeName: json["employee_name"],
employeeSalary: json["employee_salary"],
employeeAge: json["employee_age"],
profileImage: json["profile_image"],
);
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['id'] = this.id;
data['employee_name'] = this.employeeName;
data['employee_salary'] = this.employeeSalary;
data['employee_age'] = this.employeeAge;
data['profile_image'] = this.profileImage;
return data;
}
}
import'package:http/http.dart'作为http;
进口“包装:颤振/材料.省道”;
导入“dart:async”;
导入“dart:convert”;
类Demo扩展StatefulWidget{
@凌驾
_DemoState createState();
}
类_DemoState扩展了状态{
@凌驾
小部件构建(构建上下文){
返回脚手架(
appBar:appBar(
标题:文本(“演示”),
),
主体:容器(
子:列(
儿童:[
未来建设者(
future:fetchPost(),
生成器:(上下文,快照){
if(snapshot.connectionState==connectionState.done){
if(snapshot.hasError){
返回文本(“ERROR:-”+snapshot.ERROR.toString());
}
列表数据=snapshot.data;
返回新的扩展(
子项:ListView.builder(
itemCount:data.length,
itemBuilder:(上下文,索引){
返回新的ListTile(
标题:新文本(数据[索引].employeeName),
);
},
));
}否则{
//默认情况下,显示加载微调器。
返回中心(
子对象:CircularProgressIndicator(),
);
}
}),
],
),
),
);
}
Future fetchPost()异步{
var响应=
等待http.get(“http://dummy.restapiexample.com/api/v1/employees");
如果(response.statusCode==200){
//如果服务器返回OK响应,则解析JSON。
var resp=json.decode(response.body);
打印(r)