Changing the language of my application only works once - flutter

Question

I am making a Flutter application and I am making a settings page where I want to allow the user to choose the language they want. I have already tried many things but each time I have the same problem: I can only change the language once.
Here is my "settings" view:
class SettingViewState extends State<StatefulWidget> {
String _selectedLanguage = 'French';
#override
Widget build(BuildContext context) {
print('SettingViewState - build');
return Scaffold(
drawer: NavDrawableWidget(), // Hamburger menu
body: Column(
children: <Widget>[
Center(
child: Text('\n${AppSettings.strings.settingTitle}\n',
style: TextStyle(
fontSize: 18,
fontWeight: FontWeight.bold
),
),
),
Container(
child: Card(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(20),
side: BorderSide(color: Colors.black12, width: 2),
),
child: ListTile(
title: Text(AppSettings.strings.languageTitle),
leading: Icon(Icons.language),
trailing: Theme(
data: Theme.of(context).copyWith(
canvasColor: Colors.blue[50],
),
child: DropdownButton<String>(
value: _selectedLanguage,
items: [
DropdownMenuItem(
value: 'French',
child: Row(
children: <Widget>[
Image.asset(AppSettings.APP_FRENCH_FLAG,width: 30, height: 20,),
SizedBox(width: 10),
Text(AppSettings.strings.frenchTitle),
],
),
),
DropdownMenuItem(
value: 'English',
child: Row(
children: <Widget>[
Image.asset(AppSettings.APP_ENGLISH_FLAG,width: 30, height: 20,),
SizedBox(width: 10),
Text(AppSettings.strings.englishTitle),
],
),
),
],
onChanged: (String? newValue) {
setState(() {
_selectedLanguage = newValue ?? _selectedLanguage;
AppSettings.changeLanguage(_selectedLanguage);
});
},
),
),
),
),
),
],
),
);
}
}
And here is my method in my config file to change the language:
static void changeLanguage(String newLanguage)
{
APP_LANGUAGE = newLanguage;
}
Thanks in advance if you take the time to answer me and help me

Answer 1

Is Riverpod an option for your state management?
https://riverpod.dev/
I believe you can achieve what you want similar to the following:
state_providers.dart
import 'package:flutter_riverpod/flutter_riverpod.dart';
final selectedLanguageProvider = StateProvider<String>((ref) => 'English');
setting_view.dart
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:yourapp/providers/state_providers.dart';
class SettingViewState extends ConsumerWidget {
const SettingViewState({
super.key,
});
#override
Widget build(BuildContext context, WidgetRef ref) {
final selectedLanguage = ref.watch(selectedLanguageProvider);
return Column(
children: <Widget>[
Card(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(20),
side: const BorderSide(color: Colors.black12, width: 2),
),
child: ListTile(
title: const Text('Language'),
leading: const Icon(Icons.language),
trailing: Theme(
data: Theme.of(context).copyWith(
canvasColor: Colors.blue[50],
),
child: DropdownButton<String>(
value: selectedLanguage,
items: const [
DropdownMenuItem(
value: 'French',
child: Text('French'),
),
DropdownMenuItem(
value: 'English',
child: Text('English'),
),
],
onChanged: (String? newValue) {
ref.read(selectedLanguageProvider.notifier).state = newValue!;
},
),
),
),
),
],
);
}
}
It would also simplify accessing the state across Widgets as opposed to using a static settings file which I imagine you are doing. For example you can access the language state directly in an app bar widget
common_app_bar.dart
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:yourapp/providers/state_providers.dart';
class CommonAppBar extends ConsumerWidget implements PreferredSizeWidget {
const CommonAppBar({
Key? key,
}) : super(key: key);
#override
Size get preferredSize => const Size.fromHeight(kToolbarHeight);
#override
Widget build(BuildContext context, WidgetRef ref) {
final selectedLanguage = ref.watch(selectedLanguageProvider);
return AppBar(
backgroundColor: Colors.grey,
elevation: 0,
title: Text(selectedLanguage == 'English' ? 'Hello' : 'Bonjour'),
);
}
}