Why does flutter localization not work properly? - flutter

Question

I want to add the tr tag to the Flutter localization section. I am
getting an error although there is support for Tr. The error is as
follows; error: The element type 'Locale (where Locale is defined in
C:\Users\StatTark\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\intl-0.16.1\lib\src\locale.dart)'
can't be assigned to the list type 'Locale (where Locale is defined in
C:\flutter\bin\cache\pkg\sky_engine\lib\ui\window.dart)'.
error: Abstract classes can't be instantiated.
(instantiate_abstract_class at [ajanda] lib\pages\mainmenu.dart:36)
I do not understand if I am making a mistake in use, I will be glad if you help.
class MainMenu extends StatelessWidget {
MainMenu({Key key}) : super(key: key);
final _sdb = SettingsDbHelper();
#override
Widget build(BuildContext context) {
return FutureBuilder(
future: _sdb.getSettings(),
builder: (context, snapshot) {
if (snapshot.data == null) {
return MaterialApp(
localizationsDelegates: [
GlobalMaterialLocalizations.delegate,
GlobalWidgetsLocalizations.delegate
],
supportedLocales: [Locale('en','US'),Locale('tr','')], //The error is here
debugShowCheckedModeBanner: false,
home: Scaffold(
body: Center(
child: Text(proTranslate["Yükleniyor....."][Language.languageIndex]),
),
),
);
} else {
Language.languageIndex = snapshot.data[0].language;
return DynamicTheme(
defaultBrightness: Brightness.light,
data: (brightness) => ThemeData(
brightness: brightness,
fontFamily: snapshot.data[0].fontName,
floatingActionButtonTheme: FloatingActionButtonThemeData(
foregroundColor: Colors.green,
),
),
themedWidgetBuilder: (context, theme) {
return MaterialApp(
localizationsDelegates: [
GlobalMaterialLocalizations.delegate,
GlobalWidgetsLocalizations.delegate
],
supportedLocales: [Locale('en','US'),Locale('tr','')],
debugShowCheckedModeBanner: false,
theme: theme,
home: MainMenuBody(
warning: snapshot.data[0].warning,
),
// navigatorKey: navigatorKey,
);
});
}
},
);
}
}
class MainMenuBody extends StatefulWidget {....}

Answer 1

I'm coming a bit late but I just fixed this same issue I had.
I'm pretty sure your file is importing intl/locale.dart instead of flutter/material.dart as both define a Local type.
To fix it, just replace your import at the top of the file from:
import 'package:intl/locale.dart';
to
import 'package:flutter/material.dart';
and you should be OK.

Answer 2

Few suggestions you can try/test, see below.
Replace [Locale('en','US'),Locale('tr','')], with [Locale('en'),Locale('tr')],
init list of supported locales first and use it accordingly.
// init before build
final List<Locale> appSupportedLocales = [
Locale('en'),
Locale('tr')
];
// ...
// then use it like this
supportedLocales: appSupportedLocales,