Using provider between different screens and appBar in flutter - flutter

Question

I'm using Provider in my flutter app. I was able to change one widget with another one, without using set state. That was great!
My feature consist that when I tap in the button 'Añadir al carrito', a number over the shopping car change, increasing one by one.
This is the part of my code that I put in the button, that is inside the body of my scaffold using the provider.of:
final _numCompras = Provider.of<MyShoppingCart>(context);
return Padding(
padding: const EdgeInsets.only(top: 15.0),
child: GestureDetector(
onTap: () {
_numCompras.numCompras = _numCompras.numCompras + 1;
ScaffoldMessenger.of(context).showSnackBar(SnackBar(
content: const Text('Producto Añadido'),
duration: const Duration(seconds: 1),
action: SnackBarAction(
label: '',
onPressed: () {
},
),
));
},
child: Container(
height: 80,
width: double.infinity,
decoration: BoxDecoration(
color: Constants.kColorRojo,
borderRadius: BorderRadius.circular(60),
border: Border.all(width: 1, color: Colors.black),
),
child: Padding(
padding: const EdgeInsets.all(10.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text(
'Añadir al Carrito',
style: TextStyle(
color: Colors.white,
fontFamily: 'Poppins',
fontSize: 20,
),
),
SizedBox(
width: 15,
),
Icon(
Icons.shopping_cart_outlined,
color: Colors.white,
size: 30,
),
],
),
),
),
),
);
}
This is my class using ChangeNotifier
int _numCompras = 0;
get numCompras => _numCompras;
set numCompras(int newValue) {
_numCompras = newValue;
notifyListeners();
}
}
And in my main.dart I`m putting the ChangeNotifierProvider, because I thing that one contain all of the rest widgets.
class JuniorsApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MultiProvider(
providers: [
ChangeNotifierProvider<MyShoppingCart>(
create: (context) => MyShoppingCart(),
//builder: ,
)
],
child: MaterialApp(
theme: ThemeData.light().copyWith(
primaryColor: Color(0xFFd51921),
scaffoldBackgroundColor: Color(0xFFf2f2f2),
),
home: PageStart(),
initialRoute: PageStart().ID_PageStart,
routes: {
page_IniciarSesion().ID_PageIniciarSesion: (context) =>
page_IniciarSesion(),
PageStart().ID_PageStart: (context) => PageStart(),
RegistroNombrePage().ID_PageRegistroNombre: (context) =>
RegistroNombrePage()
},
debugShowCheckedModeBanner: false,
),
);
}
}
And finally the code of my appBar that is the widget that I`m changing:
Widget build(BuildContext context) {
bool _hasBackButton = hasBackArrow ?? true;
final height = MediaQuery.of(context).size.height;
final width = MediaQuery.of(context).size.width;
return Selector<MyShoppingCart,int>(
selector: (_, model) => model.numCompras,
builder: (context, numCompras, _) {
return SafeArea(
child: Material(
elevation: 15,
child: Padding(
padding: EdgeInsets.symmetric(horizontal: 16),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
if (_hasBackButton)
RoundedIconButton(
iconData: Icons.arrow_back_ios,
press: () {
Navigator.pop(context, MaterialPageRoute(
builder: (context) {
return Selector(builder: (context, numCompras, _){}, selector: (_, model) => model.numCompras);
},
)
);
}
),
Text(
this.title == null ? 'Junior \'s Tacos' : this.title,
style: Constants.kFuenteAppBar,
),
this.hasCart
? _widgetShoppingCar(context, height, width, numCompras)
: Spacer() ,
],
),
),
),
);
},
);
}
Widget _widgetShoppingCar(context, height, width, _numCompras) {
return Stack(
children: [
RoundedIconButton(
iconData: Icons.shopping_cart_outlined,
press: () {
_viewShop = !_viewShop;
this.changeAppBarShop(_viewShop);
/*Navigator.push(
context,
MaterialPageRoute(
builder: (context) => CartPage(),
),
);*/
},
),
Positioned(
bottom: height * 0.04,
left: width * 0.09,
child: Container(
width: width * 0.05,
height: height * 0.025,
decoration: BoxDecoration(
color: Colors.red[500],
border: Border.all(
color: Colors.red[500],
),
borderRadius: BorderRadius.all(Radius.circular(20))),
child: Center(
child: Text(
'${_numCompras}',
style: TextStyle(
fontWeight: FontWeight.bold,
color: Colors.white,
),
)),
),
)
],
);
}
The thing is that it works fine, but when I do Navigator.pop from the appBar. The count over the shopping car come back to zero.
Here is how its working at the moment
Could anyone give a me a tip about this?
thanks!

Answer 1

Well, if anyone have this kind of problem. The issue for me was that I have two ChangeNotifierProvider. One in my main.dart and the other one in my widget that contain the button. I remove the last one and now its working.