Made PreferencesMixin generic

lib/src/mixins/preferences_mixin.dart

@@ -1,16 +1,42 @@
 import 'package:shared_preferences/shared_preferences.dart';
 
 mixin PreferencesMixin {
-  void savePreference(key, value) async {
+  void savePreference(String key, dynamic value) async {
     final prefs = await SharedPreferences.getInstance();
-    prefs.setString(key, value);
+    if (value is bool) {
+      prefs.setBool(key, value);
+    } else if (value is double) {
+      prefs.setDouble(key, value);
+    } else if (value is int) {
+      prefs.setInt(key, value);
+    } else if (value is String) {
+      prefs.setString(key, value);
+    } else if (value is List<String>) {
+      prefs.setStringList(key, value);
+    }
   }
 
-  Future getPreference(key) async {
+  Future<T?> getPreference<T>(String key) async {
     final prefs = await SharedPreferences.getInstance();
     if (prefs.containsKey(key)) {
-      final preference = prefs.getString(key);
-      return preference ?? false;
+      if (T == bool) {
+        return prefs.getBool(key) as T;
+      } else if (T == double) {
+        return prefs.getDouble(key) as T;
+      } else if (T == int) {
+        return prefs.getInt(key) as T;
+      } else if (T == String) {
+        return prefs.getString(key) as T;
+      } else if (T == List) {
+        return prefs.getStringList(key) as T;
+      }
+    }
+  }
+
+  Future<void> deletePreference(String key) async {
+    final prefs = await SharedPreferences.getInstance();
+    if (prefs.containsKey(key)) {
+      prefs.remove(key);
     }
   }
 }

lib/src/pages/manager.dart

@@ -27,13 +27,11 @@ class _ManagerState extends State<Manager> with PreferencesMixin {
   @override
   void initState() {
     super.initState();
-    getPreference(prefWorkingDirectory).then((pref) {
-      if (pref is String) {
-        setState(() {
-          Directory.current = pref;
-        });
-        Future.delayed(Duration.zero, () => _getVms(context)); // Reload VM list when we enter the page.
-      }
+    getPreference<String>(prefWorkingDirectory).then((pref) {
+      setState(() {
+        Directory.current = pref;
+      });
+      Future.delayed(Duration.zero, () => _getVms(context)); // Reload VM list when we enter the page.
     });
 
     refreshTimer = Timer.periodic(const Duration(seconds: 5), (Timer t) {

lib/src/widgets/home_page/downloader_menu.dart

@@ -16,12 +16,10 @@ class _DownloaderMenuState extends State<DownloaderMenu> with PreferencesMixin {
   @override
   void initState() {
     super.initState();
-    getPreference(prefWorkingDirectory).then((pref) {
-      if (pref is String) {
-        setState(() {
-          Directory.current = pref;
-        });
-      }
+    getPreference<String>(prefWorkingDirectory).then((pref) {
+      setState(() {
+        Directory.current = pref;
+      });
     });
   }