How to send onPressed value to another widget Flutter - flutter

Question

I want to send data from widget to another widget, in my example I want to send onPressed value as a variable.
appBar: CancelAppBar(onPressed: ),
What should I write after onPressed (in the above code) to send the value:
Navigator.of(context).push(MaterialPageRoute(builder: (context) => UnderBuild()));
to a widget in a seperate dart file?
Following is the other file:
class CancelAppBar extends StatefulWidget implements PreferredSizeWidget {
CancelAppBar({Key? key, required this.onPressed}) : super(key: key);
final ValueGetter<String> onPressed;
static final _appBar = AppBar();
#override
Size get preferredSize => _appBar.preferredSize;
#override
_CancelAppBarState createState() => _CancelAppBarState();
}
class _CancelAppBarState extends State<CancelAppBar> {
get onPressed => null;
#override
Widget build(BuildContext context) {
return AppBar(
titleSpacing: 0.0,
title: Row(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Padding(padding: EdgeInsets.only(left: 8.w)),
IconButton(
onPressed: ,
icon: Icon(Icons.close),
)
],
),
backgroundColor: AppColors.dark,
);
}
}

Answer 1

You can access any StatefulWidget variable in the State class with widget getter, like:
Also, you can notice that:
Your onPressed variable has ValueGetter<String> type which is only a typedef to String Function()
The onPressed of IconButton widget has the type void Function()
Then you can use your variable like that:
class CancelAppBar extends StatefulWidget implements PreferredSizeWidget {
CancelAppBar({Key? key, required this.onPressed}) : super(key: key);
final ValueGetter<String> onPressed;
static final _appBar = AppBar();
#override
Size get preferredSize => _appBar.preferredSize;
#override
_CancelAppBarState createState() => _CancelAppBarState();
}
class _CancelAppBarState extends State<CancelAppBar> {
#override
Widget build(BuildContext context) {
return AppBar(
titleSpacing: 0.0,
title: Row(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Padding(padding: EdgeInsets.only(left: 8.w)),
IconButton(
onPressed: () {
/// Access your variable by [widget.onPressed]
widget.onPressed(); /// Call it inside this function because your variable doesn't match directly the [onPressed] of [IconButton] widget
},
icon: Icon(Icons.close),
)
],
),
backgroundColor: AppColors.dark,
);
}
}