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;
+  }
+}