Added follow system preference for theme

lib/helper/dark_theme_preference.dart

@@ -1,15 +1,19 @@
 import 'package:shared_preferences/shared_preferences.dart';
+import 'package:vernet/models/dark_theme_provider.dart';
 
 class DarkThemePreference {
-  static const themeStatus = 'THEMESTATUS';
+  static const themeStatus = 'THEMESTATUS_NEW';
 
-  Future<void> setDarkTheme(bool value) async {
+  Future<void> setDarkTheme(ThemePreference value) async {
     final SharedPreferences prefs = await SharedPreferences.getInstance();
-    prefs.setBool(themeStatus, value);
+    prefs.setString(themeStatus, value.name);
   }
 
-  Future<bool> getTheme() async {
+  Future<ThemePreference> getTheme() async {
     final SharedPreferences prefs = await SharedPreferences.getInstance();
-    return prefs.getBool(themeStatus) ?? false;
+    return ThemePreference.values.firstWhere(
+      (element) => element.name == prefs.getString(themeStatus),
+      orElse: () => ThemePreference.light,
+    );
   }
 }

lib/main.dart

@@ -42,7 +42,7 @@ class _MyAppState extends State<MyApp> {
   }
 
   Future<void> getCurrentAppTheme() async {
-    themeChangeProvider.darkTheme =
+    themeChangeProvider.themePref =
         await themeChangeProvider.darkThemePreference.getTheme();
   }
 

lib/models/dark_theme_provider.dart

@@ -1,15 +1,26 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
 import 'package:vernet/helper/dark_theme_preference.dart';
 
 class DarkThemeProvider with ChangeNotifier {
   DarkThemePreference darkThemePreference = DarkThemePreference();
-  bool _darkTheme = false;
+  ThemePreference _darkTheme = ThemePreference.system;
 
-  bool get darkTheme => _darkTheme;
+  ThemePreference get themePref => _darkTheme;
 
-  set darkTheme(bool value) {
+  set themePref(ThemePreference value) {
     _darkTheme = value;
     darkThemePreference.setDarkTheme(value);
     notifyListeners();
   }
+
+  bool get darkTheme {
+    if (themePref == ThemePreference.system) {
+      return SchedulerBinding.instance.platformDispatcher.platformBrightness ==
+          Brightness.dark;
+    }
+    return ThemePreference.dark == themePref;
+  }
 }
+
+enum ThemePreference { system, dark, light }