我是Flutter的新手,我尝试从“ 10.0.2.2:8000/api/membres”上的api中获取数据,但出现类似“列表动态”的错误,而不是“列表”类型的子类型。 我以抖动为例:https://flutter.dev/docs/cookbook/networking/fetch-data#complete-example
请帮助我遵循一个有用的教程,并告诉我如何解决此代码。
MyHomePage.dart
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'dart:convert';
class MyHomePage extends StatefulWidget {
const MyHomePage({Key key}) : super(key: key);
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
static const url = "10.0.2.2:8000/api/membres";
Future<List<Map<String, dynamic>>> _future;
@override
void initState() {
super.initState();
_future = fetch();
}
Future<List<Map<String, dynamic>>> fetch() {
return http
.get("http://10.0.2.2:8000/api/membres")
.then((response) {
return response.statusCode == 200
? response.body
: throw 'Error when getting data';
})
.then((body) => json.decode(body)) //
.then((list) => (list as List).cast<Map<String, dynamic>>());
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Home'),
),
body: RefreshIndicator(
onRefresh: () async {
_future = fetch();
setState(() {});
return _future;
},
child: FutureBuilder<List<Map<String, dynamic>>>(
future: _future,
builder: (context, snapshot) {
if (snapshot.hasError) {
return Center(
child: Container(
constraints: BoxConstraints.expand(),
child: SingleChildScrollView(
physics: AlwaysScrollableScrollPhysics(),
child: Text(snapshot.error.toString()),),),);}
if (!snapshot.hasData) {
return Center(
child: CircularProgressIndicator(),
);}
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (BuildContext context, int index) {
final item = snapshot.data[index];
return ListTile(
title: Text(item['nom']),
subtitle: Text(item['prenom']),
);
},
);
},
),
),
);
}
}
我用Postman测试了API,并且可以正常工作:
在模拟器中:
答案 0 :(得分:1)
您有几个问题...
您可能应该将fetch
整理为async
:
Future<Map<String, dynamic>> fetch() async {
http.Response response = await http.get('http://10.0.2.2:8000/api/membres');
if (response.statusCode != 200) return null;
return json.decode(response.body);
}
如果您查看邮递员提供的json,您会看到最上面的项目是地图-至少有一个键membres
。该键似乎包含其他地图的列表。从您的类型看来,您希望获得该列表。
如果该假设是正确的,则可以如下进行调整:
Future<List<Map<String, dynamic>>> fetch() async {
http.Response response = await http.get('http://10.0.2.2:8000/api/membres');
if (response.statusCode != 200) return null;
return List<Map<String, dynamic>>.from(json.decode(response.body)['membre']);
}