我目前正在构建一个应用程序来通过 api 读取数据,并且我正在尝试从 JSON Placeholder 解析 JSON api。
我为用户创建了一个模型类(users_future_model.dart):
class Users {
final int userID;
final String name;
final String username;
final String email;
final Address address;
Users({this.userID, this.name, this.username, this.email, this.address});
factory Users.fromJson(Map<String, dynamic> usersjson)=> Users(
userID: usersjson["id"],
name: usersjson["name"],
username: usersjson["username"],
email: usersjson["email"],
address: Address.fromJson(usersjson["address"])
);
}
class Address{
final String street;
final String suite;
final String city;
final String zipcode;
Address({this.street, this.suite, this.city, this.zipcode});
factory Address.fromJson(Map<String, dynamic> addjson){
return Address(
street: addjson["street"],
suite: addjson["suite"],
city: addjson["city"],
zipcode: addjson["zipcode"]
);
}
}
这是将 json 读入小部件的 main.dart:
import 'package:flutter/material.dart';
import 'model/users_future_model.dart';
import 'dart:convert';
import 'dart:async';
import 'package:http/http.dart' as http;
final String jsonplaceholder = "http://jsonplaceholder.typicode.com/users/";
//Future method to read the URL
Future<Users> fetchInfo() async{
final response = await http.get(jsonplaceholder);
final jsonresponse = json.decode(response.body);
return Users.fromJson(jsonresponse);
}
void main() {
runApp(new MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text("Parse JSON"),
),
body: new Center(
child: new Column(
children: <Widget>[
new FutureBuilder(
future: fetchInfo(),
builder: (context, snapshot){
if(snapshot.hasData){
return new Text(snapshot.data.email);
}else if(snapshot.hasError){
return new Text("Error ${snapshot.error}");
}
})
],
),
)
);
}
}
这是我试图读取的 JSON 信息,尽管它只是其中的一小部分:
{
id: 1,
name: "Leanne Graham",
username: "Bret",
email: "Sincere@april.biz",
address: {
street: "Kulas Light",
suite: "Apt. 556",
city: "Gwenborough",
zipcode: "92998-3874",
geo: {
lat: "-37.3159",
lng: "81.1496"
}
},
phone: "1-770-736-8031 x56442",
website: "hildegard.org",
company: {
name: "Romaguera-Crona",
catchPhrase: "Multi-layered client-server neural-net",
bs: "harness real-time e-markets"
}
}
我目前遇到的错误是:
Error type 'List<dynamic>' is not a subtype of type 'Map<String, dynamic>'
我该如何纠正这个错误?
最佳答案
API 返回 JSON 数组而不是 json 对象,因此是 List 而不是 Map。
即用户 json 是 Json Array 的第一个元素。
所以要获取第一个元素,请使用第一个索引。 内部获取信息更新
return Users.fromJson(jsonresponse[0]);
关于json - 错误 : List<dynamic> is not a subtype of type Map<String, 动态>,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/51854891/