Добавил тексты локализации

lib/main.dart

@@ -1,6 +1,17 @@
 import 'package:flutter/material.dart';
 import 'splash.dart';
 import 'consts.dart';
+import 'stock_strings.dart';
+import 'dart:async';
+import 'i18n/stock_messages_all.dart';
+import 'package:intl/intl.dart';
+
+Future<LocaleQueryData> _onLocaleChanged(Locale locale) async {
+  final String localeString = locale.toString();
+  await initializeMessages(localeString);
+  Intl.defaultLocale = localeString;
+  return StockStrings.instance;
+}
 
 /// Точка входа в приложение.
 void main() {
@@ -11,6 +22,7 @@ class Checker extends StatelessWidget {
   @override Widget build(BuildContext context) {
     return new MaterialApp(title: appName,
       home: new SplashScreen(),
+      onLocaleChanged: _onLocaleChanged,
       theme: new ThemeData(
         primaryColor: primaryColor,
         accentColor: primaryColor