1、使用model和不使用model
import 'dart:convert';
import 'dart:io';
import 'package:flutter/material.dart';
void main() {
runApp(new MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key}) : super(key: key);
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class User {
final String origin;
User(this.origin);
User.fromJson(Map<String, dynamic> json)
: origin = json['origin'];
Map<String, dynamic> toJson() =>
{
'origin': origin,
};
}
class _MyHomePageState extends State<MyHomePage> {
var _ipAddress = 'Unknown';
_getIPAddress() async {
var url = 'https://httpbin.org/ip';
var httpClient = new HttpClient();
String result;
try {
var request = await httpClient.getUrl(Uri.parse(url));
var response = await request.close();
if (response.statusCode == HttpStatus.OK) {
var json = await response.transform(Utf8Decoder()).join();
Map userMap = jsonDecode(json);
var user = new User.fromJson(userMap);
print('Howdy, ${user.origin}!');
// Map<String, dynamic> user = jsonDecode(json);
// print(' ${user['origin']}');
// var data = JSON.decode(json);
// result = data['origin'];
} else {
result =
'Error getting IP address:\nHttp status ${response.statusCode}';
}
} catch (exception) {
result = 'Failed getting IP address';
}
// If the widget was removed from the tree while the message was in flight,
// we want to discard the reply rather than calling setState to update our
// non-existent appearance.
if (!mounted) return;
setState(() {
_ipAddress = result;
});
}
@override
Widget build(BuildContext context) {
var spacer = new SizedBox(height: 32.0);
return new Scaffold(
body: new Center(
child: new Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Text('Your current IP address is:'),
new Text('$_ipAddress.'),
spacer,
new RaisedButton(
onPressed: _getIPAddress,
child: new Text('Get IP address'),
),
],
),
),
);
}
}
{
Map<String, dynamic> user = jsonDecode(json);
print(' ${user['origin']}');
}
{
Map userMap = jsonDecode(json);
var user = new User.fromJson(userMap);
print('Howdy, ${user.origin}!');
}
2、使用json_serializable
添加依赖
dependencies:
flutter:
sdk: flutter
json_annotation: ^2.0.0
dev_dependencies:
flutter_test:
sdk: flutter
build_runner: ^1.0.0
json_serializable: ^2.0.0
创建model
import 'package:json_annotation/json_annotation.dart';
class User {
User(this.origin);
String origin;
}
添加注解（part后面是类名称/添加part会报红）
part 'User.g.dart';
@JsonSerializable()
运行命令
flutter packages pub run build_runner build一次性的生成文件
flutter packages pub run build_runner watch持续性的生成文件
添加fromJson和toJson
factory User.fromJson(Map<String, dynamic> json) => _$UserFromJson(json);
Map<String, dynamic> toJson() => _$UserToJson(this);
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