How to call variables from different class in flutter

Question

I want this program to do three things. One, display the current value of my number. Two, show how much I have previously entered. Three, enter how much you want to subtract from the original value of the number.

But I am having one problem with my code. In the SubtractState class, I have an onPressed function for my FlatButton. Inside there is a variable called enteredValue. When I try to call this variable in the class 'Type' it's obviously giving me errors.

I know that I need to figure out a way to call a variable from a different class. But how should I do it?

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Container(
            child: Center(
                child: GestureDetector(
      onTap: () {
        Navigator.push(
          context,
          MaterialPageRoute(builder: (context) => Type()),
        );
      },
      child: Text(
        value.toString(),
        style: TextStyle(
          fontSize: 50.0,
        ),
      ),
    ))));
  }
}

class Type extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        debugShowCheckedModeBanner: false,
        home: Scaffold(
            body: Container(
                child: Center(
                    child: Column(
                        mainAxisAlignment: MainAxisAlignment.center,
                        children: <Widget>[
              GestureDetector(
                child: Text("You Entered ${globals.enteredValue} previously"),
                onTap: () {
                  Navigator.push(
                    context,
                    MaterialPageRoute(builder: (context) => Subtract()),
                  );
                },
              )
            ])))));
  }
}

class Subtract extends StatefulWidget {
  @override
  SubtractState createState() => SubtractState();
}

class SubtractState extends State<Subtract> {
  final _controller = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            appBar: AppBar(
              elevation: 0,
              leading: IconButton(
                  color: Colors.black,
                  icon: Icon(Icons.arrow_back_ios),
                  onPressed: () => Navigator.pop(context)),
            ),
            body: Container(
                padding: const EdgeInsets.all(30.0),
                child: Container(
                  child: Center(
                      child: Column(
                          mainAxisAlignment: MainAxisAlignment.center,
                          children: [
                        TextFormField(
                            textInputAction: TextInputAction.done,
                            controller: _controller,
                            keyboardType: TextInputType.number),
                        FlatButton(
                          child: Text("Subtract"),
                          onPressed: () {
                            //check if we can parse it
                            if (int.tryParse(_controller.text) == null)
                              return; //can't parse it
                            globals.enteredValue = int.parse(_controller.text);
                            setState(() {
                              value -= globals.enteredValue;
                            });
                            Navigator.push(
                              context,
                              MaterialPageRoute(builder: (context) => MyApp()),
                            );
                          },
                        ),
                      ])),
                ))));
  }
}

int value = 0;

Houssem · Accepted Answer · 2020-03-01 12:15:24Z

2

I suggest one of the existing easy solutions to use a global library to share your application variables between classes :
Create a dart file named globals.dart

globals.dart :

library YOUR_PACKAGE_NAME.globals;
int x = 1 ;

class1 :

 import 'package:YOUR_PACKAGE_NAME/globals.dart' as globals;
 print(globals.x) ; //prints 1 
 globals.x= 2 ;

in your class2 :

import 'package:YOUR_PACKAGE_NAME/globals.dart' as globals;
print(globals.x) ; //prints 2

answered Mar 1, 2020 at 12:15

Houssem

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1 Comment

Md. Kamrul Amin Over a year ago

You are a star.

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