如何根据flutter中的API响应处理不同设备上的登录

Question

我对如何处理不同设备的多次登录感到困惑，当有其他设备刚刚登录到同一用户时，我想将功能返回到登录布局

Future<EventArticleList> getEventArticleList(String token) async {
BuildContext context;
Map<String, String> headers = {
"Accept": "application/json",
"Authorization": "Bearer $token"
};
var response = await client.get('$endpoint/', headers: headers);
if (response.statusCode == 200) {
print("Masuk Data");
return EventArticleList.fromJson(
json.decode(response.body),
);
} else if (response.statusCode == 401) {
print("401");
return Navigator.of(context)
.pushNamedAndRemoveUntil(RoutePaths.Login, (_) => false);
} else {
throw Exception("ini Eror apa ?");
}
}

编译出现了，我试图将导航器添加回状态。代码==401

NoSuchMethodError:方法"ancestorStateOfType"在null 上被调用

Answer 1

尝试此代码

您的主类

import 'package:flutter/material.dart';
import 'package:flutterapitut/view/adddata.dart';
import 'package:flutterapitut/view/dashboard.dart';
import 'package:flutterapitut/view/login.dart';
import 'package:flutterapitut/view/register.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
final String title='';
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter CRUD API',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: LoginPage(title: 'Flutter CRUD API'),
routes: <String,WidgetBuilder>{
'/dashboard' : (BuildContext context) => new Dashboard(title:title),
'/login' : (BuildContext context) => new LoginPage(title:title),
},
);
}
}

您的数据库帮助程序类

import 'package:http/http.dart' as http;
import 'dart:convert';
import 'package:shared_preferences/shared_preferences.dart';
class DatabaseHelper{
String serverUrl = "http://flutterapitutorial.codeforiraq.org/api";
var status ;
var token ;
loginData(String email , String password) async{
String myUrl = "$serverUrl/login1";
final response = await  http.post(myUrl,
headers: {
'Accept':'application/json'
},
body: {
"email": "$email",
"password" : "$password"
} ) ;
status = response.body.contains('error');
var data = json.decode(response.body);
if(status){
print('data : ${data["error"]}');
}else{
print('data : ${data["token"]}');
_save(data["token"]);
}
}

_save(String token) async {
final prefs = await SharedPreferences.getInstance();
final key = 'token';
final value = token;
prefs.setString(key, value);
}

read() async {
final prefs = await SharedPreferences.getInstance();
final key = 'token';
final value = prefs.get(key ) ?? 0;
print('read : $value');
} 
}

您的登录类

import 'package:flutter/material.dart';
import 'package:flutterapitut/Controllers/databasehelper.dart';
import 'package:flutterapitut/view/dashboard.dart';
import 'package:flutterapitut/view/register.dart';
import 'package:shared_preferences/shared_preferences.dart';

class LoginPage extends StatefulWidget{
LoginPage({Key key , this.title}) : super(key : key);
final String title;
@override
LoginPageState  createState() => LoginPageState();
}
class LoginPageState extends State<LoginPage> {

read() async {
final prefs = await SharedPreferences.getInstance();
final key = 'token';
final value = prefs.get(key ) ?? 0;
if(value != '0'){
Navigator.of(context).push(
new MaterialPageRoute(
builder: (BuildContext context) => new Dashboard(),
)
);
}
}
@override
initState(){
read();
}


DatabaseHelper databaseHelper = new DatabaseHelper();
String msgStatus = '';
final TextEditingController _emailController = new TextEditingController();
final TextEditingController _passwordController = new TextEditingController();

_onPressed(){
setState(() {
if(_emailController.text.trim().toLowerCase().isNotEmpty &&
_passwordController.text.trim().isNotEmpty ){
databaseHelper.loginData(_emailController.text.trim().toLowerCase(),
_passwordController.text.trim()).whenComplete((){
if(databaseHelper.status){
_showDialog();
msgStatus = 'Check email or password';
}else{
Navigator.pushReplacementNamed(context, '/dashboard');

}
});
}
});
}

@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Login',
home: Scaffold(
appBar: AppBar(
title:  Text('Login'),
),
body: Container(
child: ListView(
padding: const EdgeInsets.only(top: 62,left: 12.0,right: 12.0,bottom: 12.0),
children: <Widget>[
Container(
height: 50,
child: new TextField(
controller: _emailController,
keyboardType: TextInputType.emailAddress,
decoration: InputDecoration(
labelText: 'Email',
hintText: 'Place your email',
icon: new Icon(Icons.email),
),
),
),
Container(
height: 50,
child: new TextField(
controller: _passwordController,
keyboardType: TextInputType.text,
decoration: InputDecoration(
labelText: 'Password',
hintText: 'Place your password',
icon: new Icon(Icons.vpn_key),
),
),
),
new Padding(padding: new EdgeInsets.only(top: 44.0),),
Container(
height: 50,
child: new RaisedButton(
onPressed: _onPressed,
color: Colors.blue,
child: new Text(
'Login',
style: new TextStyle(
color: Colors.white,
backgroundColor: Colors.blue),),
),
),
new Padding(padding: new EdgeInsets.only(top: 44.0),),
Container(
height: 50,
child: new Text(
'$msgStatus',
textAlign: TextAlign.center,
overflow: TextOverflow.ellipsis,
style: TextStyle(fontWeight: FontWeight.bold),
),
),
new Padding(padding: new EdgeInsets.only(top: 44.0),),
Container(
height: 50,
child: new FlatButton(
onPressed: ()=>Navigator.of(context).push(
new MaterialPageRoute(
builder: (BuildContext context) => new RegisterPage(),
)
)
,
color: Colors.blue,
child: new Text(
'Register',
style: new TextStyle(
color: Colors.white,
),),
),
),
],
),
),
),
);
}

void _showDialog(){
showDialog(
context:context ,
builder:(BuildContext context){
return AlertDialog(
title: new Text('Failed'),
content:  new Text('Check your email or password'),
actions: <Widget>[
new RaisedButton(
child: new Text(
'Close',
),
onPressed: (){
Navigator.of(context).pop();
},
),
],
);
}
);
}
}

这里的Dashboard是您成功登录后期望导航的类想要更多代码请访问这里我希望这能正确运行