Flutter setState public var to another page? - flutter

Question

how to setState public var to another page?
int x = 1;
that was in public
in the first page text(x) i want to setstate from the other page
my first page is
class AddFullRequest extends StatefulWidget {
#override
_AddFullRequestState createState() => _AddFullRequestState();
}
class _AddFullRequestState extends State<AddFullRequest> {
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: <Widget>[
Text(x),
GestureDetector(
onTap: (){
Navigator.of(context).push(new MaterialPageRoute(
builder: (BuildContext context) => AddItemScr()));
},
child: Text('goto'),
),
],
),
);
}
in the other page button to ++ the var in the first page
my other page is
class AddItemScr extends StatefulWidget {
#override
_AddItemScrState createState() => _AddItemScrState();
}
class _AddItemScrState extends State<AddItemScr> {
#override
Widget build(BuildContext context) {
return Scaffold(
body: WillPopScope(onWillPop: (){
Navigator.of(context).pop();
},
child: Column(
children: <Widget>[
FlatButton(onPressed: (){setState(() {
x++;
});}, child: Text('pluss'),)
],
),
),
);
}
}
please help me with this

Answer 1

You can use the callback pattern. In this example, a function (onPressed) is passed to the child. The child calls the function when a button is pressed:
class AddFullRequest extends StatefulWidget {
#override
_AddFullRequestState createState() => _AddFullRequestState();
}
class _AddFullRequestState extends State<AddFullRequest> {
int _x = 0;
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: <Widget>[
Text("$_x"),
GestureDetector(
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (context) => AddItemScr(
onPressed: () => setState(() => _x++),
),
),
);
},
child: Text('goto'),
),
],
),
);
}
}
class AddItemScr extends StatelessWidget {
final VoidCallback onPressed;
const AddItemScr({
Key key,
#required this.onPressed,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: <Widget>[
FlatButton(
onPressed: onPressed,
child: Text('Increment'),
),
],
),
);
}
}

Answer 2

You can pass variables between screens. NavigatorState#pop supports passing objects that you can await in the previous screen and set it to it's value.
class AddFullRequest extends StatefulWidget {
#override
_AddFullRequestState createState() => _AddFullRequestState();
}
class _AddFullRequestState extends State<AddFullRequest> {
int x = 0;
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: <Widget>[
Text('$x'),
GestureDetector(
onTap: () async {
final result = await Navigator.of(context).push<int>(
MaterialPageRoute(
builder: (_) => AddItemScr(variable: x),
),
);
x = result;
setState(() {});
},
child: Text('goto'),
),
],
),
);
}
}
class AddItemScr extends StatefulWidget {
final int variable;
AddItemScr({this.variable});
#override
_AddItemScrState createState() => _AddItemScrState();
}
class _AddItemScrState extends State<AddItemScr> {
int _variable;
#override
void initState() {
_variable = widget.variable;
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: <Widget>[
FlatButton(
onPressed: () {
setState(() {
_variable++;
});
},
child: Text('pluss'),
),
FlatButton(
onPressed: () {
Navigator.of(context).pop(_variable);
},
child: Text('go back'),
),
],
),
);
}
}