How to pass a variable reference between different routes? - flutter

Question

Im writing a simple gamebook game in flutter with menu, game and options route. In option route there is button that on pressed should delete all saved games.
Right at this moment Im loading saved games on application launch from SharedPreferences. Right after loading them I set up boolean _savedGame that im using in 'Continue' button in menu route and 'Delete saved games' button in options route to activate or deactivate them. The whole problem is - i dont know how to change variables in menu route from option route. When im creating option route I give it _savedGame so that it knows if it should render active or deactivated button.
PS. Yes, I know that right now im sending option route a copy of _savedGame variable.
Menu route option page button.
RaisedButton(
onPressed: () => Navigator.push(
context,
MaterialPageRoute(
builder: (context) => OptionsPage(_savedGame),
),
),
Option page
class OptionsPageState extends State<OptionsPage> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(
"Options",
style: TextStyle(color: Colors.white),
),
backgroundColor: Colors.blueGrey[900],
),
body: Container(
alignment: Alignment.center,
color: Colors.cyan,
child: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
RaisedButton(
child:
Text('Delete saved games', style: TextStyle(fontSize: 40)),
onPressed:
widget.isGameSaved ? () => _showWarning(context) : null,
),
const SizedBox(height: 30),
RaisedButton(
child: Text('Back', style: TextStyle(fontSize: 40)),
onPressed: () {
Navigator.pop(context);
},
),
])),
),
);
}
Future<void> _showWarning(BuildContext context) {
return showDialog<void>(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: Text('Are you sure you want to delete saved game?'),
actions: <Widget>[
FlatButton(
child: Text('No'),
onPressed: () {
Navigator.of(context).pop();
},
),
FlatButton(
child: Text('Yes'),
onPressed: () {
saveGame('empty');
Navigator.of(context).pop();
setState(() {
widget.isGameSaved = false;
});
},
),
],
);
},
);
}
}
How do I "setState" for variables in different routes?

Answer 1

What you could do is have an InheritedWidget (call it say GameStateWidget) above your Navigator (or MaterialApp if you're using its navigator). In the InheritedWidget have a ValueNotifier, say savedGame that has the value you want to share.
Then in the route where you need to set the value
GameStateWidget.of(context).savedGame.value = ...
And in the route where you need the value
ValueListenableBuilder(
valueListenable: GameStateWidget.of(context).savedGame,
builder: (context, savedGameValue, child) => ...
)