Load user preferences at start of app. Manage locations: user is able to add locations by lat and lon to shared preferences

lib/components/settings_form.dart

@@ -1,5 +1,5 @@
 import 'package:flutter/material.dart';
-import 'package:shared_preferences/shared_preferences.dart';
+import 'package:wetter/services/user_preferences.dart';
 
 class SettingsForm extends StatefulWidget {
   const SettingsForm({Key? key}) : super(key: key);
@@ -9,20 +9,13 @@ class SettingsForm extends StatefulWidget {
 }
 
 class SettingsFormState extends State<SettingsForm> {
-  SharedPreferences? prefs;
   int _daysToLoad = 7;
   final _formKey = GlobalKey<FormState>();
 
   @override
   void initState() {
+    _daysToLoad = UserPreferences.preferences!.getInt("daysToLoad") ?? 7;
     super.initState();
-    initializePreferences().whenComplete(() => setState(() {
-          _daysToLoad = prefs?.getInt("daysToLoad") ?? 7;
-        }));
-  }
-
-  Future<void> initializePreferences() async {
-    prefs = await SharedPreferences.getInstance();
   }
 
   @override
@@ -35,12 +28,13 @@ class SettingsFormState extends State<SettingsForm> {
               value: _daysToLoad.toDouble(),
               min: 1.0,
               max: 14.0,
-              divisions: 14,
+              divisions: 13,
               label: _daysToLoad.round().toString(),
               onChanged: (double value) {
                 setState(() {
                   _daysToLoad = value.round();
-                  prefs?.setInt("daysToLoad", _daysToLoad);
+                  UserPreferences.preferences!
+                      .setInt("daysToLoad", _daysToLoad);
                 });
               },
             )