Dark mode settings save to SharedPreferences

lib/src/app.dart

@@ -1,5 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
+import 'package:quickgui/src/globals.dart';
+import 'package:quickgui/src/mixins/preferences_mixin.dart';
 import 'package:quickgui/src/model/app_theme.dart';
 import 'package:quickgui/src/pages/main_page.dart';
 
@@ -10,16 +12,30 @@ class App extends StatefulWidget {
   State<App> createState() => _AppState();
 }
 
-class _AppState extends State<App> {
+class _AppState extends State<App> with PreferencesMixin {
   @override
   Widget build(BuildContext context) {
-    return Consumer<AppTheme>(
-      builder: (context, appTheme, _) => MaterialApp(
-        theme: ThemeData(primarySwatch: Colors.pink),
-        darkTheme: ThemeData.dark(),
-        themeMode: appTheme.themeMode,
-        home: const MainPage(title: 'Quickgui - A Flutter frontend for Quickget and Quickemu'),
-      ),
+    return FutureBuilder<bool?>(
+      future: getPreference<bool>(prefThemeMode),
+      builder: (context, AsyncSnapshot<bool?> snapshot) {
+        if (snapshot.connectionState == ConnectionState.done) {
+          if (snapshot.data != null) {
+            context.read<AppTheme>().useDarkMode = snapshot.data!;
+          }
+          return Consumer<AppTheme>(
+            builder: (context, appTheme, _) => MaterialApp(
+              theme: ThemeData(primarySwatch: Colors.pink),
+              darkTheme: ThemeData.dark(),
+              themeMode: appTheme.themeMode,
+              home: const MainPage(title: 'Quickgui - A Flutter frontend for Quickget and Quickemu'),
+            ),
+          );
+        } else {
+          return const Center(
+            child: CircularProgressIndicator(),
+          );
+        }
+      },
     );
   }
 }

lib/src/globals.dart

@@ -2,3 +2,4 @@ import 'dart:io';
 
 var gIsSnap = Platform.environment['SNAP']?.isNotEmpty ?? false;
 const String prefWorkingDirectory = 'workingDirectory';
+const String prefThemeMode = 'themeMode';

lib/src/widgets/left_menu.dart

@@ -1,10 +1,12 @@
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
+import 'package:quickgui/src/globals.dart';
 import 'package:quickgui/src/mixins/app_version.dart';
+import 'package:quickgui/src/mixins/preferences_mixin.dart';
 import 'package:quickgui/src/model/app_theme.dart';
 
-class LeftMenu extends StatelessWidget {
+class LeftMenu extends StatelessWidget with PreferencesMixin {
   const LeftMenu({Key? key}) : super(key: key);
 
   @override
@@ -27,6 +29,7 @@ class LeftMenu extends StatelessWidget {
                     value: Theme.of(context).brightness == Brightness.dark,
                     onChanged: (value) {
                       appTheme.useDarkMode = value;
+                      savePreference(prefThemeMode, value);
                     },
                   ),
                 ],