Can toggle dark mode from menu on tablet mode

lib/helpers/preferences_helper.dart

@@ -76,6 +76,12 @@ class PreferencesHelper {
   ApplicationPreferences get preferences => ApplicationPreferences(
         enableDarkMode: getBool(PreferencesKeyList.ENABLE_DARK_THEME),
       );
+
+  /// Apply new preferences
+  Future<void> setPreferences(ApplicationPreferences preferences) async {
+    await setBool(
+        PreferencesKeyList.ENABLE_DARK_THEME, preferences.enableDarkMode);
+  }
 }
 
 PreferencesHelper preferences() {

lib/models/application_preferences.dart

@@ -5,9 +5,9 @@ import 'package:flutter/cupertino.dart';
 /// @author Pierre Hubert
 
 class ApplicationPreferences {
-  final bool enableDarkMode;
+  bool enableDarkMode;
 
-  const ApplicationPreferences({
+  ApplicationPreferences({
     @required this.enableDarkMode,
   }) : assert(enableDarkMode != null);
 }

lib/ui/widgets/tablet_mode/tablet_appbar_widget.dart

@@ -1,5 +1,6 @@
 import 'package:comunic/helpers/events_helper.dart';
 import 'package:comunic/helpers/notifications_helper.dart';
+import 'package:comunic/helpers/preferences_helper.dart';
 import 'package:comunic/models/count_unread_notifications.dart';
 import 'package:comunic/ui/routes/main_route/main_route.dart';
 import 'package:comunic/ui/screens/notifications_screen.dart';
@@ -7,6 +8,7 @@ import 'package:comunic/ui/screens/unread_conversations_screen.dart';
 import 'package:comunic/ui/widgets/safe_state.dart';
 import 'package:comunic/ui/widgets/tablet_mode/appbar_custom_dropdown_widget.dart';
 import 'package:comunic/utils/intl_utils.dart';
+import 'package:comunic/utils/ui_utils.dart';
 import 'package:flutter/material.dart';
 
 /// Comunic tablet AppBar widget
@@ -84,6 +86,14 @@ class _ComunicTabletAppBarWidgetState
         PopupMenuButton<_MenuItemCallback>(
           offset: Offset(0, 50),
           itemBuilder: (c) => [
+            // Toggle dark theme
+            _MainMenuItem(
+                label: tr("Night mode"),
+                icon: preferences().preferences.enableDarkMode
+                    ? Icons.brightness_2
+                    : Icons.wb_sunny,
+                onTap: _toggleDarkMode),
+
             // Sign out
             _MainMenuItem(
                 label: tr("Sign out"),
@@ -95,6 +105,15 @@ class _ComunicTabletAppBarWidgetState
       ],
     );
   }
+
+  /// Toggle dark mode
+  void _toggleDarkMode() async {
+    final prefs = preferences().preferences;
+    prefs.enableDarkMode = !prefs.enableDarkMode;
+    await preferences().setPreferences(prefs);
+
+    applyNewThemeSettings(context);
+  }
 }
 
 typedef _MenuItemCallback = void Function();