Passing dates(variables) between Classes? - dart

Question

I need to pass variables between classes.
for example:
archive ClassN1.dart
The Class N1 content variable1 = 0
archive ClassN2.dart
the class N2 calculate sumVariables = Variable1 * 2;
For days I've been looking for information about it.
From already thank you very much!
import 'package:flutter/material.dart';
import 'Funtion_Calculate.dart';
class DatesPrincipal extends StatelessWidget {
get left => null;
#override
Widget build(BuildContext context) {
return new Container(
child: Row(
children: <Widget>[
new Container(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[ //First linea of dates
NumberDates(),
StatusNPS(),
PutDatesNPS()
],
),
)
],
),
);
}
}
class NumberDates extends StatefulWidget {
#override
_NumberDatesState createState() => _NumberDatesState();
}
class _NumberDatesState extends State<NumberDates> {
var adecuado = '0';
Widget build(BuildContext context) {
Widget iconList;
return iconList = DefaultTextStyle.merge(
style: descTextStyle,
child: Container(
child: new Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Container(
child: Column(
children: <Widget>[
Text(adecuado,
style: TextStyle(
fontSize: 18
),
),
Padding(
padding: EdgeInsets.all(4),
),
Text('Adecuado')
],
),
width: 100.0,
),
],
),
)
);
}
}
The archive number2.dart
- status = adecuado * 2
class StatusNPS extends StatefulWidget {
#override
_StatusNPSState createState() => _StatusNPSState();
}
class _StatusNPSState extends State<StatusNPS> {
var status = '82.9'; // status = adecuado * 2
Widget build(BuildContext context) {
Widget iconList;
return iconList = DefaultTextStyle.merge(
style: descTextStyle,
child: Container(
width: 400.0,
padding: EdgeInsets.fromLTRB(0.0, 10.0, 0.0, 10.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(status, style: TextStyle(
fontFamily: 'SF Pro',
),),
Text(' %', style: TextStyle(
fontSize: 65.0,
fontFamily:'SF Pro',
),)
],
)
)
);
}
}