How to use shared preferences to save token in flutter? - flutter

Question

I want to keep the user token in after the user successfully login in flutter.I am trying to save device token to SharedPreferences so I can use it in other widgets,but error is always : Invalid argument(s) (value): Must not be null . How i can save ID and access token ?
My code :
Future<User> login(String username, String password) async {
await checkInternet();
Map<String, String> headers = {
'Content-type': 'application/json',
'Accept': 'application/json',
// 'Authorization': 'Bearer $token'
};
Map<String, String> body = {'username': username, 'password': password};
var response = await http.post(Uri.parse(ApiUtil.AUTH_LOGIN),
headers: headers, body: jsonEncode(body));
switch (response.statusCode) {
case 200:
var body = jsonDecode(response.body);
// print(body);
var data = body['user'];
// print(data);
User user = User.fromJson(data);
await _saveUser(user.id, user.access_token);
return user;
case 404:
throw ResourceNotFound('User');
break;
case 422:
throw UnProcessedEntity();
break;
case 401:
throw LoginFailed();
default:
return null;
break;
}
}
Future<void> _saveUser(int id, String access_token) async {
SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
sharedPreferences.setInt('id', id);
sharedPreferences.setString('access_token', access_token);
}
}
and rhis the user model :
class User {
int id;
String name;
String email;
String username;
String phone;
String access_token;
String activeboxe_id;
String adress;
DateTime email_verifed_at;
User(this.name, this.email, this.username, this.phone, this.activeboxe_id,
this.adress, this.email_verifed_at,
[this.access_token, this.id]);
User.fromJson(Map<String, dynamic> jsonObject) {
this.id = jsonObject['id'];
this.name = jsonObject['name'];
this.email = jsonObject['email'];
this.phone = jsonObject['phone'];
this.access_token = jsonObject['access_token'];
this.activeboxe_id = jsonObject['activeboxe_id'];
this.adress = jsonObject['adress'];
this.email_verifed_at = jsonObject['email_verifed_at'];
this.username = jsonObject['username'];
}
}

Answer 1

First check if the values you are trying to save are not null and setInt or setString is an async function so you need to add await before them
Future<void> _saveUser(int id, String access_token) async {
SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
await sharedPreferences.setInt('id', id);
await sharedPreferences.setString('access_token', access_token);
}
And your User class is not return the .fromJson if you have noticed
class User {
int id;
String name;
String email;
String username;
String phone;
String access_token;
String activeboxe_id;
String adress;
DateTime email_verifed_at;
User(this.name, this.email, this.username, this.phone, this.activeboxe_id,
this.adress, this.email_verifed_at,
[this.access_token, this.id]);
// return a User object here
factory User.fromJson(Map<String, dynamic> jsonObject) => User({
this.id = jsonObject['id'];
this.name = jsonObject['name'];
this.email = jsonObject['email'];
this.phone = jsonObject['phone'];
this.access_token = jsonObject['access_token'];
this.activeboxe_id = jsonObject['activeboxe_id'];
this.adress = jsonObject['adress'];
this.email_verifed_at = jsonObject['email_verifed_at'];
this.username = jsonObject['username'];
});
}