问题：
未处理的异常：类型“\u InternalLinkedHashMap”不是类型转换中“List”类型的子类型？
白光耀
以下是回应
{
"overview": "A ticking-time-bomb insomniac and a slippery soap salesman channel primal male aggression into a shocking new form of therapy. Their concept catches on, with underground "fight clubs" forming in every town, until an eccentric gets in the way and ignites an out-of-control spiral toward oblivion.",
"title": "Fight Club",
}
模型
class Movies {
String title;
String overview;
Movies(
{this.title , this.overview});
factory Movies.fromJson(Map <String, dynamic> parsedJson){
return Movies(title: parsedJson['title'] , overview: parsedJson['overview']);
}
}
和
Future <List<Movies>> fetchMovies () async {
var response = await http.get(url);
var jsonData = jsonDecode(response.body) as List ;
List<Movies> movies = jsonData.map((e) => Movies.fromJson(e)).toList();
print(movies.length);
return movies;
}
我收到此错误（未处理的异常：键入“\u InternalLinkedHashMap
共有3个答案
曾德水
看看他的回答
[
{
"overview":"A ticking-time-bomb insomniac and a slippery soap salesman channel primal male aggression into a shocking new form of therapy. Their concept catches on, with underground \"fight clubs\" forming in every town, until an eccentric gets in the way and ignites an out-of-control spiral toward oblivion.",
"title":"Fight Club"
},
{
"overview":"A ticking-time-bomb insomniac and a slippery soap salesman channel primal male aggression into a shocking new form of therapy. Their concept catches on, with underground fight clubs forming in every town, until an eccentric gets in the way and ignites an out-of-control spiral toward oblivion.",
"title":"second Club"
}
]
模型
// To parse this JSON data, do
//
// final movies = moviesFromJson(jsonString);
import 'dart:convert';
List<Movies> moviesFromJson(String str) => List<Movies>.from(json.decode(str).map((x) => Movies.fromJson(x)));
String moviesToJson(List<Movies> data) => json.encode(List<dynamic>.from(data.map((x) => x.toJson())));
class Movies {
Movies({
this.overview,
this.title,
});
String overview;
String title;
factory Movies.fromJson(Map<String, dynamic> json) => Movies(
overview: json["overview"],
title: json["title"],
);
Map<String, dynamic> toJson() => {
"overview": overview,
"title": title,
};
}
UI页面：
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:json_parsing_example/models.dart';
// To parse this JSON data, do
//
// final user = userFromJson(jsonString);
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Users'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
bool _isLoading = false;
List<Movies> dataList = List();
Future<String> loadFromAssets() async {
return await rootBundle.loadString('json/parse.json');
}
@override
void initState() {
super.initState();
getData();
}
getData() async {
setState(() {
_isLoading = true;
});
String jsonString = await loadFromAssets();
final movies = moviesFromJson(jsonString);
dataList = movies;
setState(() {
_isLoading = false;
});
}
// In your case you just check out this code check out the model class
/* Future <List<Movies>> fetchMovies () async {
var response = await http.get(url);
return moviesFromJson(response.body);
} */
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text(widget.title),
),
body: _isLoading
? Center(
child: CircularProgressIndicator(),
)
: Container(
child: ListView.builder(
itemCount: dataList.length,
shrinkWrap: true,
itemBuilder: (context, i) {
return Card(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Text(dataList[i].overview),
));
}),
),
);
}
}
要告诉你的是概述的值有双引号，这就是为什么可能会有一些解析问题，只要检查代码，让我知道它是否工作。
庄浩言
您可以在下面复制粘贴运行完整代码
您可以使用moviesFromJson并使用FutureBuilder
代码片段显示
List<Movies> moviesFromJson(String str) =>
List<Movies>.from(json.decode(str).map((x) => Movies.fromJson(x)));
if (response.statusCode == 200) {
return moviesFromJson(jsonString);
工作演示
完整代码
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
List<Movies> moviesFromJson(String str) =>
List<Movies>.from(json.decode(str).map((x) => Movies.fromJson(x)));
String moviesToJson(List<Movies> data) =>
json.encode(List<dynamic>.from(data.map((x) => x.toJson())));
class Movies {
Movies({
this.overview,
this.title,
});
String overview;
String title;
factory Movies.fromJson(Map<String, dynamic> json) => Movies(
overview: json["overview"],
title: json["title"],
);
Map<String, dynamic> toJson() => {
"overview": overview,
"title": title,
};
}
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<List<Movies>> _future;
Future<List<Movies>> fetchMovies() async {
String jsonString = '''
[{
"overview" : "with underground \\"fight clubs\\" forming in every town, until an eccentric gets in the way and ignites an out-of-control spiral toward oblivion",
"title" : "Fight Club"
},
{
"overview" : "test overview",
"title" : "test title"
}
]
''';
var response = http.Response(jsonString, 200);
if (response.statusCode == 200) {
return moviesFromJson(jsonString);
} else {
print(response.statusCode);
}
}
@override
void initState() {
_future = fetchMovies();
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: FutureBuilder(
future: _future,
builder: (context, AsyncSnapshot<List<Movies>> 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.length,
itemBuilder: (context, index) {
return Card(
elevation: 6.0,
child: Padding(
padding: const EdgeInsets.only(
top: 6.0,
bottom: 6.0,
left: 8.0,
right: 8.0),
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(snapshot.data[index].title),
Spacer(),
Expanded(
child: Text(
snapshot.data[index].overview,
),
),
],
),
));
});
}
}
}));
}
}
方通
您试图将jsonData强制转换为List，但解码器说它是Map类型（您的响应也显示了它的Map类型）
Future <List<Movies>> fetchMovies () async {
var response = await http.get(url);
var jsonData = jsonDecode(response.body);
if(jsonData is List) //check if it's a List
return List<Movies>.from(jsonData.map(map) => Movies.fromJson(map));
else if(jsonData is Map) //check if it's a Map
return [Movies.fromJson(jsonData)]; //return a List of length 1
}
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