add structure

lib/widget/localization/app_translations.dart

@@ -0,0 +1,42 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:ui';
+
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart' show rootBundle;
+
+class AppTranslations {
+  Locale locale;
+  static Map<dynamic, dynamic> _localisedValues;
+
+  AppTranslations(Locale locale) {
+    this.locale = locale;
+  }
+
+  static AppTranslations of(BuildContext context) {
+    return Localizations.of<AppTranslations>(context, AppTranslations);
+  }
+
+  static Future<AppTranslations> load(Locale locale) async {
+    AppTranslations appTranslations = AppTranslations(locale);
+    String jsonContent = await rootBundle
+        .loadString("assets/local/localization_${locale.languageCode}.json");
+    _localisedValues = json.decode(jsonContent);
+    return appTranslations;
+  }
+
+  get currentLanguage => locale.languageCode;
+
+  String text(String key, {List<String> translationVariables}) {
+    String value = _localisedValues[key];
+    if (value == null) {
+      return "$key not found";
+    }
+    if (translationVariables != null) {
+      translationVariables.asMap().forEach((i, s) {
+        value = value.replaceAll("{$i}", s);
+      });
+    }
+    return value;
+  }
+}

lib/widget/localization/app_translations_delegate.dart

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+import 'dart:async';
+import 'package:flutter/material.dart';
+import 'app_translations.dart';
+import 'transalation.dart';
+
+class AppTranslationsDelegate extends LocalizationsDelegate<AppTranslations> {
+  final Locale newLocale;
+
+  const AppTranslationsDelegate({this.newLocale});
+
+  @override
+  bool isSupported(Locale locale) {
+    return Translation().supportedLanguagesCodes.contains(locale.languageCode);
+  }
+
+  @override
+  Future<AppTranslations> load(Locale locale) {
+    return AppTranslations.load(newLocale ?? locale);
+  }
+
+  @override
+  bool shouldReload(LocalizationsDelegate<AppTranslations> old) {
+    return true;
+  }
+}

lib/widget/localization/transalation.dart

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+import 'dart:ui';
+
+typedef void LocaleChangeCallback(Locale locale);
+
+class Translation {
+  static final Translation _translation = Translation._internal();
+
+  factory Translation() {
+    return _translation;
+  }
+
+  Translation._internal();
+
+  final List<String> supportedLanguages = [
+    "English",
+    "မြန်မာ ",
+  ];
+
+  final List<String> supportedLanguagesCodes = ["en", "mu"];
+
+  //returns the list of supported Locales
+  Iterable<Locale> supportedLocales() =>
+      supportedLanguagesCodes.map<Locale>((language) => Locale(language, ""));
+
+  //function to be invoked when changing the language
+  LocaleChangeCallback onLocaleChanged;
+}