Passing Variables Between Two Classes in Flutter

Question

I am making register and login pages in flutter and facing a problem as I want to use the same variables 'email' and 'password' declared inside class _MyHomePage in main.dart file

to another class SignupPage in signup.dart file.

I already imported the files but I can not use the values in both classes

class _MyHomePageState extends State<MyHomePage> {
 int _counter = 0;

String _email = '';
String _password = '';

final formKey = new GlobalKey<FormState>();

FormType _formType = FormType.login;

bool validateAndSave() {
final form = formKey.currentState;
if (form.validate()) {
  form.save();
  return true;
 //      print('Form is Valid  Email: $_email, Password: $_password');
}
return false;
}

Answer 1

You can pass the data when you navigate your screen in following way.

Navigator.push(
                context,
                MaterialPageRoute(
                  builder: (context) => SignUp(email: emailvariable,pass: passvariable),
                ),

in following way you can receive data

class SignUp extends StatefulWidget {

  final email;
  final pass; 
  SignUp({Key key,this.email,this.pass}) : super(key: key);

  @override
  _SignUpState createState() => _SignUpState();
}

now in state widget you can access email and pass variable as

widget.pass and widget.email

Answer 2

There are two approaches for that

Pass values through class constructor

If you don't want to go back and forth you can use this

Just in the second page use like this

class Register extends StatefulWidget {
  Register({Key key, this.email, this.pass});

  final String email;
  final String pass;

  @override
  _RegisterState createState() => _RegisterState();
}

class _RegisterState extends State<Register> {

  @override
  Widget build(BuildContext context) {
    print(widget.email);
    print(widget.pass);
    // to use state class values you need to use the widget as the parent class object
    return Container(
    );
  }
}

To pass the values in constructor

Navigator.push(
  context,
  MaterialPageRoute(
    builder: (context) => Register(email: email, pass: pass),
  ),

Store the values in global scope before routing to another page

If you have to route multiple times and even require these values further, you store the values in global file before routing to another page and access there

Make one file

global.dart

library my_project.global;

// set default values for the initial run
String email = '';
String pass = '';

To access the values

import 'global.dart' as global;

main() {
 // import the global.dart file to access the variables across the application
 global.email = '[email protected]';
 print(global.email);
}