Global variable in Dart/Flutter - flutter

Question

i wrote an function to login user by rest api in flutter. I want to use response from post but i don't know how to export my variable into another file.
I want use userID, but i dont know how,
can somebody help me?
class LoginScreenState extends State<LoginScreen>{
makeLoginRequest(String email, password) async {
SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
Map data = {
'email':email,
'password':password
};
var jsonResponse;
var url = 'http://10.0.2.2:80/user/login';
var response = await http.post(url, body:data);
if(response.statusCode == 200){
jsonResponse = json.decode(response.body);
int userID = jsonResponse['id'];//HERE
if(jsonResponse != null){
setState(() {
_isLoading = false;
});
sharedPreferences.setString("token", jsonResponse['token']);
Navigator.of(context).pushAndRemoveUntil(MaterialPageRoute(builder: (BuildContext context) => UserPage()), (Route<dynamic> route) => false);
}
}

Answer 1

In your UserPage use a variable to get the ID.
Example:
class UserPage extends StatefulWidget {
final int userId;
UserPage({#required this.userId});
#override
_UserPageState createState() => _UserPageState();
}
class _UserPageState extends State<UserPage> {
#override
Widget build(BuildContext context) {
return Container();
}
}
While navigating to UserPage after login pass the userID:
Navigator.of(context).pushAndRemoveUntil(MaterialPageRoute(builder: (BuildContext context) => UserPage(userId: userID)), (Route<dynamic> route) => false);
When you want to get the value of userId in UserPage, you can use it in following way: widget.userId