Flutter: Calling SetState() from another class - flutter

Question

I am trying to make a simple image that appears or disappears when a button is pushed. This button resides in a separate class to the image, so in Flutter this creates a massive headache of an issue.
I have read many forums on this and I have tried all the solutions posed but none of them are working for me.
What I am trying to do:
class SinglePlayerMode extends StatefulWidget {
#override
SinglePlayerModeParentState createState() => SinglePlayerModeParentState();
}
class SinglePlayerModeParentState extends State<SinglePlayerMode> {\
bool coinVisible = false;
toggleCoin() {
setState(() {
coinVisible = !coinVisible;
});
}
Widget topMenuRow() {
return Stack(
children: [
Column(
children: [
coinVisible == true ?
Padding(
padding: EdgeInsets.all(50),
child: Container(
height: 60,
width: 60,
color: Colors.blueGrey[0],
decoration: BoxDecoration(
color: Colors.blueAccent,
image: DecorationImage(
image: ExactAssetImage('lib/images/coin_head.jpg'),
fit: BoxFit.cover,
),
),
),
) : Container(
height: 60,
width: 60,
color: Colors.black,
),
],
),
],
);
}
#override
Widget build(BuildContext context) {
return Scaffold(
child: ListView(
padding: EdgeInsets.symmetric(horizontal: 10.0, vertical: 10.0),
children: [
topMenuRow(),
SizedBox(height: 40),
],
),
),
);
}
And this is the separate class which I would like to trigger the SetState() on coinVisible from:
class dropDownMenu extends StatefulWidget { #override
_dropDownMenuState createState() => _dropDownMenuState();
}
class _dropDownMenuState extends State<dropDownMenu> {
#override
Widget build(BuildContext context) {
return Stack(
children: <Widget> [
Column(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
Container(
child: Opacity(
opacity: 0.0,
child: FloatingActionButton(
heroTag: null,
onPressed: (){
//SOMEHOW CALL SetState() ON coinVisble HERE!
},
),
),
);
}
}
But nothing I have tried is working, and I have lost hours.

Answer 1

It simple, you need to send your SinglePlayMode::toggleCoin function as callback to dropDownMenu class.
class dropDownMenu extends StatefulWidget {
final _callback; // callback reference holder
//you will pass the callback here in constructor
dropDownMenu( {#required void toggleCoinCallback() } ) :
_callback = toggleCoinCallback;
#override
_dropDownMenuState createState() => _dropDownMenuState();
}
class _dropDownMenuState extends State<dropDownMenu> {
#override
Widget build(BuildContext context) {
return Stack(
children: <Widget> [
Column(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
Container(
child: Opacity(
opacity: 0.0,
child: FloatingActionButton(
heroTag: null,
onPressed: (){
widget?._callback(); // callback calling
},
),
),
);
}
}
Then when you create a dropDownMenu class instance in your SinglePlayerMode class you will do
dropDownMenu(
toggleCoinCallback: toogleCoin,
);