Flutter MaterialApp with navigatorKey and key is not restarting - flutter

Question

When testing, press the increment button a few times to view if the app restarts.
I was trying to "restart" a toy app in Flutter. I was using the old counter example and after modifying it the behavior is not the expected.
For example, with this code:
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
final GlobalKey<NavigatorState> _navigatorKey = GlobalKey<NavigatorState>();
UniqueKey _materialKey;
UniqueKey _homeKey;
#override
void initState() {
super.initState();
_awaitAndRun();
}
#override
Widget build(BuildContext context) {
return MaterialApp(
key: _materialKey,
navigatorKey: _navigatorKey,
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(
key: _homeKey,
title: 'Flutter Demo Home Page',
),
);
}
Future<void> _awaitAndRun() async {
print('Starting delay... Please press the button before the time ends.');
await Future<dynamic>.delayed(Duration(seconds: 5));
setState(() {
_materialKey = UniqueKey();
_homeKey = UniqueKey();
});
print('Has been the screen reloaded?');
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
The awaitAndRun function should restart the App because I am setting the _materialKey and _homeKey as new instances. As part of it, the MyHomePage widget also should be rebuilt (because the key value has changed) but it didn't.
I can understand it's because the _navigatorKey is "saving" the state of the MaterialApp but the MyHomePage should be rebuild because its key has changed!
It's even more strange because if I remove the _materialKey (as shown in the code below), the MyHomePage widget gets rebuilt.
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
final GlobalKey<NavigatorState> _navigatorKey = GlobalKey<NavigatorState>();
UniqueKey _materialKey;
UniqueKey _homeKey;
#override
void initState() {
super.initState();
_awaitAndRun();
}
#override
Widget build(BuildContext context) {
return MaterialApp(
//key: _materialKey,
navigatorKey: _navigatorKey,
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(
key: _homeKey,
title: 'Flutter Demo Home Page',
),
);
}
Future<void> _awaitAndRun() async {
print('Starting delay... Please press the button before the time ends.');
await Future<dynamic>.delayed(Duration(seconds: 5));
setState(() {
_materialKey = UniqueKey();
_homeKey = UniqueKey();
});
print('Has been the screen reloaded?');
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
So it doesn't have any sense for me, why does this happen? Why when I set the _materialKey the MyHomePage widget doesn't get rebuilt?

Answer 1

It's pretty normal. Flutter always target safe and clean state and doesn't keep any item usually time. You can use a lot of methods, so I think should provider
You need to game states keep to app state, so I created ToysGame(sample) and added count property, you can use and change this property so unaffected state changes.
Firstly wrap single provider instance to your app page.
home: Provider(
create: (context) => ToysGame(),
child: MyHomePage(
key: _homeKey,
title: 'Flutter Demo Home Page',
),
),
After doesn't keep count on in page state, you should use toys state with provider.
Text(
Provider.of<ToysGame>(context).count.toString(),
style: Theme.of(context).textTheme.headline4,
),
And you want to change value
void _incrementCounter() {
Provider.of<ToysGame>(context, listen: false).count++;
setState(() {});
}
Finally, it's done. I added on my stackhelpover repo with restart app lib name.
(You read provider package and maybe other feature help for you [ change notifier or multi-provider ])
StackHelpOver