diff --git a/lib/widgets/desktop/desktop_me.dart b/lib/widgets/desktop/desktop_me.dart
index c94af66..c60a139 100644
--- a/lib/widgets/desktop/desktop_me.dart
+++ b/lib/widgets/desktop/desktop_me.dart
@@ -16,9 +16,9 @@ import '../../utils/util_web.dart'
     if (dart.library.io) '../../utils/util_io.dart';
 import '../../utils/utils.dart';
 
-late MediaQueryData mediaQuery;
-late double statusBarHeight;
-late double screenHeight;
+MediaQueryData? mediaQuery;
+double? statusBarHeight;
+double? screenHeight;
 
 class DesktopMe extends StatefulWidget {
   final Key? key;
@@ -67,8 +67,8 @@ class DesktopMeState extends State<DesktopMe> {
     }
 
     mediaQuery ??= MediaQuery.of(context);
-    screenHeight ??= mediaQuery.size.height;
-    statusBarHeight ??= mediaQuery.padding.top;
+    screenHeight ??= mediaQuery!.size.height;
+    statusBarHeight ??= mediaQuery!.padding.top;
 
     Widget userInfo = GestureDetector(
       child: Container(
diff --git a/lib/widgets/mobile/mobile_me.dart b/lib/widgets/mobile/mobile_me.dart
index 9757036..e5a8531 100644
--- a/lib/widgets/mobile/mobile_me.dart
+++ b/lib/widgets/mobile/mobile_me.dart
@@ -20,9 +20,9 @@ import '../../utils/util_web.dart'
     if (dart.library.io) '../../utils/util_io.dart';
 import '../../utils/utils.dart';
 
-late MediaQueryData mediaQuery;
-late double statusBarHeight;
-late double screenHeight;
+MediaQueryData? mediaQuery;
+double? statusBarHeight;
+double? screenHeight;
 
 class MobileMe extends StatefulWidget {
   final Key? key;
@@ -43,7 +43,7 @@ class MobileMeState extends State<MobileMe> {
   User? _user;
 
   late ShopScrollCoordinator _shopCoordinator;
-  late ShopScrollController _pageScrollController;
+  ShopScrollController? _pageScrollController;
   final double _sliverAppBarInitHeight = 165.0;
   final double _appBarHeight = 85.0;
 
@@ -65,13 +65,13 @@ class MobileMeState extends State<MobileMe> {
     }
 
     mediaQuery ??= MediaQuery.of(context);
-    screenHeight ??= mediaQuery.size.height;
-    statusBarHeight ??= mediaQuery.padding.top;
+    screenHeight ??= mediaQuery!.size.height;
+    statusBarHeight ??= mediaQuery!.padding.top;
 
     _pageScrollController ??=
         _shopCoordinator.pageScrollController(_sliverAppBarInitHeight * -1.0);
     _shopCoordinator.pinnedHeaderSliverHeightBuilder ??= () {
-      return statusBarHeight + kToolbarHeight + _appBarHeight;
+      return statusBarHeight! + kToolbarHeight + _appBarHeight;
     };
 
     _listScrollController1 = _shopCoordinator.newChildScrollController();
diff --git a/lib/widgets/mobile/mobile_product_detail_page.dart b/lib/widgets/mobile/mobile_product_detail_page.dart
index 605900f..d5b5120 100644
--- a/lib/widgets/mobile/mobile_product_detail_page.dart
+++ b/lib/widgets/mobile/mobile_product_detail_page.dart
@@ -23,10 +23,10 @@ import '../../widgets/general/add_remove_button.dart';
 import '../../widgets/general/carousel.dart';
 import '../../widgets/general/show_price.dart';
 
-late MediaQueryData mediaQuery;
-late double statusBarHeight;
-late double screenHeight;
-late double screenWidth;
+MediaQueryData? mediaQuery;
+double? statusBarHeight;
+double? screenHeight;
+double? screenWidth;
 
 class MobileProductDetailPage extends StatefulWidget {
   final Business business;
@@ -45,12 +45,12 @@ class MobileProductDetailPage extends StatefulWidget {
 class MobileProductDetailPageState extends State<MobileProductDetailPage>
     with SingleTickerProviderStateMixin {
   late ShopScrollCoordinator _shopCoordinator;
-  late ShopScrollController _pageScrollController;
+  ShopScrollController? _pageScrollController;
 
   late TabController _tabController;
 
-  late double _sliverAppBarInitHeight;
-  late double _sliverAppBarMaxHeight;
+  double? _sliverAppBarInitHeight;
+  double? _sliverAppBarMaxHeight;
   final double _tabBarHeight = 50;
 
   ProductDetail? productDetail;
@@ -75,18 +75,18 @@ class MobileProductDetailPageState extends State<MobileProductDetailPage>
     refresh = false;
 
     mediaQuery ??= MediaQuery.of(context);
-    screenHeight ??= mediaQuery.size.height;
-    screenWidth ??= mediaQuery.size.width;
-    statusBarHeight ??= mediaQuery.padding.top;
+    screenHeight ??= mediaQuery!.size.height;
+    screenWidth ??= mediaQuery!.size.width;
+    statusBarHeight ??= mediaQuery!.padding.top;
 
     _sliverAppBarInitHeight ??= screenWidth;
     _sliverAppBarMaxHeight ??= screenWidth;
 
     _pageScrollController ??= _shopCoordinator
-        .pageScrollController(_sliverAppBarMaxHeight - _sliverAppBarInitHeight);
+        .pageScrollController(_sliverAppBarMaxHeight! - _sliverAppBarInitHeight!);
 
     _shopCoordinator.pinnedHeaderSliverHeightBuilder ??= () {
-      return statusBarHeight + kToolbarHeight + _tabBarHeight;
+      return statusBarHeight! + kToolbarHeight + _tabBarHeight;
     };
 
     return Scaffold(
@@ -110,10 +110,10 @@ class MobileProductDetailPageState extends State<MobileProductDetailPage>
                 },
               ),
               backgroundColor: Theme.of(context).primaryColor,
-              expandedHeight: _sliverAppBarMaxHeight - 30.0,
+              expandedHeight: _sliverAppBarMaxHeight! - 30.0,
               flexibleSpace: FlexibleSpaceBar(
                 background: Carousel(
-                  height: _sliverAppBarInitHeight + 0.0,
+                  height: _sliverAppBarInitHeight! + 0.0,
                   pages: _getProductPictures(context),
                   autoPlay: false,
                 ),
diff --git a/lib/widgets/mobile/shop.dart b/lib/widgets/mobile/shop.dart
index 9c72e3a..5edf2af 100644
--- a/lib/widgets/mobile/shop.dart
+++ b/lib/widgets/mobile/shop.dart
@@ -37,10 +37,10 @@ import 'product_item.dart';
 import 'product_search.dart';
 import 'shopping_cart_bar.dart';
 
-late MediaQueryData mediaQuery;
-late double statusBarHeight;
-late double screenWidth;
-late double screenHeight;
+MediaQueryData? mediaQuery;
+double? statusBarHeight;
+double? screenWidth;
+double? screenHeight;
 
 class Shop extends StatefulWidget {
   final int? businessId;
@@ -80,11 +80,11 @@ class ShopState extends State<Shop>
   bool refresh = false;
 
   late ShopScrollCoordinator _shopCoordinator;
-  late ShopScrollController _pageScrollController;
+  ShopScrollController? _pageScrollController;
   late TabController _tabController;
   final double _sliverAppBarInitHeight = 150.0;
   final double _tabBarHeight = 50.0;
-  late double _sliverAppBarMaxHeight;
+  double? _sliverAppBarMaxHeight;
 
   ShopScrollController? _listScrollController1;
   late ShopScrollController _listScrollController2;
@@ -204,17 +204,17 @@ class ShopState extends State<Shop>
     }
 
     mediaQuery ??= MediaQuery.of(context);
-    screenWidth ??= mediaQuery.size.width;
-    screenHeight ??= mediaQuery.size.height;
-    statusBarHeight ??= mediaQuery.padding.top;
+    screenWidth ??= mediaQuery!.size.width;
+    screenHeight ??= mediaQuery!.size.height;
+    statusBarHeight ??= mediaQuery!.padding.top;
 
-    _sliverAppBarMaxHeight ??= screenHeight - 150.0;
+    _sliverAppBarMaxHeight ??= screenHeight! - 150.0;
 
     _pageScrollController ??= _shopCoordinator
-        .pageScrollController(_sliverAppBarMaxHeight - _sliverAppBarInitHeight);
+        .pageScrollController(_sliverAppBarMaxHeight! - _sliverAppBarInitHeight);
 
     _shopCoordinator.pinnedHeaderSliverHeightBuilder ??= () {
-      return statusBarHeight + kToolbarHeight + _tabBarHeight;
+      return statusBarHeight! + kToolbarHeight + _tabBarHeight;
     };
 
     refresh = false;
@@ -513,8 +513,8 @@ class ShopState extends State<Shop>
         Positioned(
           top: 0,
           right: 0,
-          left: screenWidth - 100,
-          bottom: screenHeight - 100,
+          left: screenWidth! - 100,
+          bottom: screenHeight! - 100,
           child: Image.asset(
             'assets/images/under_renovation.png',
             width: 200.0,
@@ -953,7 +953,7 @@ class ShopState extends State<Shop>
                   color: Colors.white,
                 )),
             Container(
-              width: mediaQuery.size.width - 30.0,
+              width: mediaQuery!.size.width - 30.0,
               padding: EdgeInsets.only(right: 10.0, bottom: 10.0),
               child: new Text(
                 _business!.bulletin!.isEmpty ? '' : _business!.bulletin!,