Implement Localization Management

+ Implement change language by Bloc Architecture
+ Adapt lint and test rule

lib/data/model/language_model.dart

@@ -0,0 +1,24 @@
+import 'dart:ui';
+
+enum Language {
+  english(
+    Locale('en', 'US'),
+    'English',
+  ),
+  spanish(
+    Locale('es', 'ES'),
+    'Español',
+  ),
+  french(
+    Locale('fr', 'FR'),
+    'Français',
+  );
+
+  const Language(
+    this.value,
+    this.text,
+  );
+
+  final Locale value;
+  final String text;
+}

lib/l10n/app_en.arb

@@ -0,0 +1,6 @@
+{
+  "title": "Hello, World!",
+  "subtitle": "Welcome to Localization",
+  "description": "You have pushed the button this many times:",
+  "switch_language": "Switch language"
+}

lib/l10n/app_es.arb

@@ -0,0 +1,7 @@
+
+{
+"title": "¡Hola, Mundo!",
+"subtitle": "Bienvenido a Localización",
+"description": "Has pulsado el botón tantas veces:",
+"switch_language": "Cambiar idioma"
+}

lib/l10n/app_fr.arb

@@ -0,0 +1,6 @@
+{
+"title": "Bonjour",
+"subtitle": "Bienvenue dans Localisation",
+"description": "Vous avez appuyé sur le bouton autant de fois :",
+"switch_language": "Changer de langue"
+}

lib/main.dart

@@ -1,125 +1,47 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
+import 'presentation/bloc/language_bloc/language_bloc.dart';
+import 'presentation/homescreen/home_page.dart';
 
 void main() {
-  runApp(const MyApp());
+  runApp(
+    MultiBlocProvider(
+      providers: [
+        BlocProvider<LanguageBloc>(
+          create: (_) => LanguageBloc(),
+        ),
+      ],
+      child: MyApp(),
+    ),
+  );
 }
 
 class MyApp extends StatelessWidget {
   const MyApp({super.key});
 
-  // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
-    return MaterialApp(
-      title: 'Flutter Demo',
-      theme: ThemeData(
-        // This is the theme of your application.
-        //
-        // TRY THIS: Try running your application with "flutter run". You'll see
-        // the application has a purple toolbar. Then, without quitting the app,
-        // try changing the seedColor in the colorScheme below to Colors.green
-        // and then invoke "hot reload" (save your changes or press the "hot
-        // reload" button in a Flutter-supported IDE, or press "r" if you used
-        // the command line to start the app).
-        //
-        // Notice that the counter didn't reset back to zero; the application
-        // state is not lost during the reload. To reset the state, use hot
-        // restart instead.
-        //
-        // This works for code too, not just values: Most code changes can be
-        // tested with just a hot reload.
-        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
-        useMaterial3: true,
-      ),
-      home: const MyHomePage(title: 'Flutter Demo Home Page'),
-    );
-  }
-}
-
-class MyHomePage extends StatefulWidget {
-  const MyHomePage({super.key, required this.title});
-
-  // This widget is the home page of your application. It is stateful, meaning
-  // that it has a State object (defined below) that contains fields that affect
-  // how it looks.
-
-  // This class is the configuration for the state. It holds the values (in this
-  // case the title) provided by the parent (in this case the App widget) and
-  // used by the build method of the State. Fields in a Widget subclass are
-  // always marked "final".
-
-  final String title;
-
-  @override
-  State<MyHomePage> createState() => _MyHomePageState();
-}
-
-class _MyHomePageState extends State<MyHomePage> {
-  int _counter = 0;
-
-  void _incrementCounter() {
-    setState(() {
-      // This call to setState tells the Flutter framework that something has
-      // changed in this State, which causes it to rerun the build method below
-      // so that the display can reflect the updated values. If we changed
-      // _counter without calling setState(), then the build method would not be
-      // called again, and so nothing would appear to happen.
-      _counter++;
-    });
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    // This method is rerun every time setState is called, for instance as done
-    // by the _incrementCounter method above.
-    //
-    // The Flutter framework has been optimized to make rerunning build methods
-    // fast, so that you can just rebuild anything that needs updating rather
-    // than having to individually change instances of widgets.
-    return Scaffold(
-      appBar: AppBar(
-        // TRY THIS: Try changing the color here to a specific color (to
-        // Colors.amber, perhaps?) and trigger a hot reload to see the AppBar
-        // change color while the other colors stay the same.
-        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
-        // Here we take the value from the MyHomePage object that was created by
-        // the App.build method, and use it to set our appbar title.
-        title: Text(widget.title),
-      ),
-      body: Center(
-        // Center is a layout widget. It takes a single child and positions it
-        // in the middle of the parent.
-        child: Column(
-          // Column is also a layout widget. It takes a list of children and
-          // arranges them vertically. By default, it sizes itself to fit its
-          // children horizontally, and tries to be as tall as its parent.
-          //
-          // Column has various properties to control how it sizes itself and
-          // how it positions its children. Here we use mainAxisAlignment to
-          // center the children vertically; the main axis here is the vertical
-          // axis because Columns are vertical (the cross axis would be
-          // horizontal).
-          //
-          // TRY THIS: Invoke "debug painting" (choose the "Toggle Debug Paint"
-          // action in the IDE, or press "p" in the console), to see the
-          // wireframe for each widget.
-          mainAxisAlignment: MainAxisAlignment.center,
-          children: <Widget>[
-            const Text(
-              'You have pushed the button this many times:',
-            ),
-            Text(
-              '$_counter',
-              style: Theme.of(context).textTheme.headlineMedium,
-            ),
+    return BlocBuilder<LanguageBloc, LanguageState>(
+      builder: (context, state) {
+        return MaterialApp(
+          title: 'Flutter Demo',
+          locale: state.selectedLanguage.value,
+          localizationsDelegates: const [
+            AppLocalizations.delegate,
+            GlobalMaterialLocalizations.delegate,
+            GlobalWidgetsLocalizations.delegate,
+            GlobalCupertinoLocalizations.delegate,
           ],
-        ),
-      ),
-      floatingActionButton: FloatingActionButton(
-        onPressed: _incrementCounter,
-        tooltip: 'Increment',
-        child: const Icon(Icons.add),
-      ), // This trailing comma makes auto-formatting nicer for build methods.
+          supportedLocales: const [
+            Locale('en'), // English
+            Locale('es'), // Spanish
+            Locale('fr'), // French
+          ],
+          home: const MyHomePage(),
+        );
+      },
     );
   }
 }

lib/presentation/bloc/language_bloc/language_bloc.dart

@@ -0,0 +1,19 @@
+import 'package:bloc/bloc.dart';
+import 'package:equatable/equatable.dart';
+import '../../../data/model/language_model.dart';
+part 'language_event.dart';
+part 'language_state.dart';
+
+const languagePrefsKey = 'languagePrefs';
+
+class LanguageBloc extends Bloc<LanguageEvent, LanguageState> {
+  LanguageBloc() : super(const LanguageState()) {
+    on<ChangeLanguage>(onChangeLanguage);
+  }
+  Future<void> onChangeLanguage(
+    ChangeLanguage event,
+    Emitter<LanguageState> emit,
+  ) async {
+    emit(state.copyWith(selectedLanguage: event.selectedLanguage));
+  }
+}

lib/presentation/bloc/language_bloc/language_event.dart

@@ -0,0 +1,19 @@
+part of 'language_bloc.dart';
+
+abstract class LanguageEvent extends Equatable {
+  const LanguageEvent();
+
+  @override
+  List<Object> get props => [];
+}
+
+class ChangeLanguage extends LanguageEvent {
+
+  const ChangeLanguage({
+    required this.selectedLanguage,
+  });
+  final Language selectedLanguage;
+
+  @override
+  List<Object> get props => [selectedLanguage];
+}

lib/presentation/bloc/language_bloc/language_state.dart

@@ -0,0 +1,25 @@
+part of 'language_bloc.dart';
+
+class LanguageState extends Equatable {
+  const LanguageState({
+    this.selectedLanguage = Language.english, // Default to English
+  });
+
+  final Language selectedLanguage;
+
+  @override
+  List<Object> get props => [selectedLanguage];
+
+  LanguageState copyWith({Language? selectedLanguage}) {
+    return LanguageState(
+      selectedLanguage: selectedLanguage ?? this.selectedLanguage,
+    );
+  }
+}
+
+class LanguageInitial extends LanguageState {
+  const LanguageInitial()
+      : super(
+          selectedLanguage: Language.english,
+        ); // Explicitly set default language to English
+}

lib/presentation/homescreen/home_page.dart

@@ -0,0 +1,50 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+import '../widget/language_widget.dart';
+
+class MyHomePage extends StatefulWidget {
+  const MyHomePage({super.key});
+  @override
+  State<MyHomePage> createState() => _MyHomePageState();
+}
+
+class _MyHomePageState extends State<MyHomePage> {
+  int _counter = 0;
+
+  void _incrementCounter() {
+    setState(() {
+      _counter++;
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
+        title: Text(AppLocalizations.of(context)?.title ?? ''),
+      ),
+      body: Center(
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: <Widget>[
+            Text(
+              AppLocalizations.of(context)?.subtitle ?? '',
+            ),
+            Text(
+              '$_counter',
+              style: Theme.of(context).textTheme.headlineMedium,
+            ),
+            const SizedBox(height: 20),
+            const LanguageSelector(), // Add the language selector here
+          ],
+        ),
+      ),
+      floatingActionButton: FloatingActionButton(
+        onPressed: _incrementCounter,
+        tooltip: 'Increment',
+        child: const Icon(Icons.add),
+      ),
+    );
+  }
+}

lib/presentation/widget/language_widget.dart

@@ -0,0 +1,44 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+
+import '../../data/model/language_model.dart';
+import '../bloc/language_bloc/language_bloc.dart';
+
+class LanguageSelector extends StatelessWidget {
+  const LanguageSelector({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Row(
+      mainAxisAlignment: MainAxisAlignment.center,
+      children: [
+        ElevatedButton(
+          onPressed: () {
+            context.read<LanguageBloc>().add(
+                  ChangeLanguage(selectedLanguage: Language.english),
+                );
+          },
+          child: const Text('English'),
+        ),
+        const SizedBox(width: 8),
+        ElevatedButton(
+          onPressed: () {
+            context.read<LanguageBloc>().add(
+                  ChangeLanguage(selectedLanguage: Language.spanish),
+                );
+          },
+          child: const Text('Español'),
+        ),
+        const SizedBox(width: 8),
+        ElevatedButton(
+          onPressed: () {
+            context.read<LanguageBloc>().add(
+                  ChangeLanguage(selectedLanguage: Language.french),
+                );
+          },
+          child: const Text('Français'),
+        ),
+      ],
+    );
+  }
+}