diff --git a/lib/localization/app_translations.dart b/lib/localization/app_translations.dart
index 0c8cc59..f578c5a 100644
--- a/lib/localization/app_translations.dart
+++ b/lib/localization/app_translations.dart
@@ -6,14 +6,14 @@ import 'package:flutter/material.dart';
 import 'package:flutter/services.dart' show rootBundle;
 
 class AppTranslations {
-  Locale locale;
-  static Map<dynamic, dynamic> _localisedValues;
+  late Locale locale;
+  static late Map<dynamic, dynamic> _localisedValues;
 
   AppTranslations(Locale locale) {
     this.locale = locale;
   }
 
-  static AppTranslations of(BuildContext context) {
+  static AppTranslations? of(BuildContext context) {
     return Localizations.of<AppTranslations>(context, AppTranslations);
   }
 
@@ -27,7 +27,7 @@ class AppTranslations {
 
   get currentLanguage => locale.languageCode;
 
-  String text(String key, {List<String> translationVariables}) {
+  String text(String key, {List<String>? translationVariables}) {
     String value = _localisedValues[key];
     if (value == null) {
       return "$key not found";
diff --git a/lib/localization/app_translations_delegate.dart b/lib/localization/app_translations_delegate.dart
index 010d1ac..c90f302 100644
--- a/lib/localization/app_translations_delegate.dart
+++ b/lib/localization/app_translations_delegate.dart
@@ -15,7 +15,7 @@ class AppTranslationsDelegate extends LocalizationsDelegate<AppTranslations> {
 
   @override
   Future<AppTranslations> load(Locale locale) {
-    return AppTranslations.load(newLocale ?? locale);
+    return AppTranslations.load(newLocale);
   }
 
   @override
diff --git a/lib/localization/transalation.dart b/lib/localization/transalation.dart
index 634ae80..8a548b9 100644
--- a/lib/localization/transalation.dart
+++ b/lib/localization/transalation.dart
@@ -23,5 +23,5 @@ class Translation {
       supportedLanguagesCodes.map<Locale>((language) => Locale(language, ""));
 
   //function to be invoked when changing the language
-  LocaleChangeCallback? onLocaleChanged;
+  late LocaleChangeCallback onLocaleChanged;
 }
diff --git a/lib/pages/contact/contact_editor.dart b/lib/pages/contact/contact_editor.dart
index 5a7cf50..8092c2f 100644
--- a/lib/pages/contact/contact_editor.dart
+++ b/lib/pages/contact/contact_editor.dart
@@ -1,6 +1,5 @@
 import 'package:fcs/domain/vo/contact.dart';
 import 'package:fcs/helpers/theme.dart';
-import 'package:fcs/localization/app_translations.dart';
 import 'package:fcs/pages/contact/model/contact_model.dart';
 import 'package:fcs/pages/main/util.dart';
 import 'package:fcs/pages/widgets/input_text.dart';
@@ -14,7 +13,7 @@ import 'package:provider/provider.dart';
 import 'widgets.dart';
 
 class ContactEditor extends StatefulWidget {
-  final Contact contact;
+  final Contact? contact;
   const ContactEditor({this.contact});
   @override
   _ContactEditorState createState() => _ContactEditorState();
@@ -29,22 +28,23 @@ class _ContactEditorState extends State<ContactEditor> {
   TextEditingController _facebook = new TextEditingController();
 
   bool _isLoading = false;
-  bool isNew;
+  bool isNew = false;
 
+  Contact? _contact;
   @override
   void initState() {
+    if (widget.contact != null) _contact = widget.contact!;
     super.initState();
-    if (widget.contact != null) {
-      isNew = false;
-      _usaPhone.text = widget.contact.usaContactNumber;
-      _mmPhone.text = widget.contact.mmContactNumber;
-      _usaAddress.text = widget.contact.usaAddress;
-      _mmAddress.text = widget.contact.mmAddress;
-      _email.text = widget.contact.emailAddress;
-      _facebook.text = widget.contact.facebookLink;
-    } else {
-      isNew = true;
-    }
+    isNew = widget.contact == null;
+  }
+
+  initContact() {
+    _usaPhone.text = _contact?.usaContactNumber ?? '';
+    _mmPhone.text = _contact?.mmContactNumber ?? '';
+    _usaAddress.text = _contact?.usaAddress ?? '';
+    _mmAddress.text = _contact?.mmAddress ?? '';
+    _email.text = _contact?.emailAddress ?? '';
+    _facebook.text = _contact?.facebookLink ?? '';
   }
 
   @override
@@ -136,14 +136,17 @@ class _ContactEditorState extends State<ContactEditor> {
       _isLoading = true;
     });
     try {
-      widget.contact.usaContactNumber = _usaPhone.text;
-      widget.contact.mmContactNumber = _mmPhone.text;
-      widget.contact.usaAddress = _usaAddress.text;
-      widget.contact.mmAddress = _mmAddress.text;
-      widget.contact.emailAddress = _email.text;
-      widget.contact.facebookLink = _facebook.text;
-      var contactModel = Provider.of<ContactModel>(context, listen: false);
-      await contactModel.saveContact(widget.contact);
+      _contact?.usaContactNumber = _usaPhone.text;
+      _contact?.mmContactNumber = _mmPhone.text;
+      _contact?.usaAddress = _usaAddress.text;
+      _contact?.mmAddress = _mmAddress.text;
+      _contact?.emailAddress = _email.text;
+      _contact?.facebookLink = _facebook.text;
+      if (this._contact != null) {
+        var contactModel = Provider.of<ContactModel>(context, listen: false);
+        await contactModel.saveContact(_contact!);
+      }
+
       Navigator.pop(context);
     } catch (e) {
       showMsgDialog(context, "Error", e.toString());
diff --git a/lib/pages/contact/contact_page.dart b/lib/pages/contact/contact_page.dart
index 404b2ac..0023a31 100644
--- a/lib/pages/contact/contact_page.dart
+++ b/lib/pages/contact/contact_page.dart
@@ -1,7 +1,6 @@
 import 'package:fcs/domain/entities/setting.dart';
 import 'package:fcs/domain/vo/contact.dart';
 import 'package:fcs/helpers/theme.dart';
-import 'package:fcs/localization/app_translations.dart';
 import 'package:fcs/pages/contact/contact_editor.dart';
 import 'package:fcs/pages/main/model/main_model.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
diff --git a/lib/pages/contact/widgets.dart b/lib/pages/contact/widgets.dart
index 40a78f6..f8f38b8 100644
--- a/lib/pages/contact/widgets.dart
+++ b/lib/pages/contact/widgets.dart
@@ -7,25 +7,25 @@ Widget itemTitle(BuildContext context, String textKey) {
   return Padding(
     padding: const EdgeInsets.only(left: 18.0, top: 25, bottom: 5),
     child: Text(
-      AppTranslations.of(context).text(textKey),
+      AppTranslations.of(context)!.text(textKey),
       style: TextStyle(
           fontWeight: FontWeight.bold, fontSize: 18, color: Colors.black),
     ),
   );
 }
 
-Widget subItemTitle(BuildContext context, String textKey, {IconData iconData}) {
+Widget subItemTitle(BuildContext context, String textKey, {IconData? iconData}) {
   return Padding(
     padding: const EdgeInsets.only(left: 0, top: 0, bottom: 0),
     child: Row(
       children: [
         Icon(
-          iconData,
+          iconData, 
           color: primaryColor,
         ),
         SizedBox(width: 10),
         Text(
-          AppTranslations.of(context).text(textKey),
+          AppTranslations.of(context)!.text(textKey),
           style: TextStyle(
               fontWeight: FontWeight.w700, fontSize: 15, color: primaryColor),
         ),
@@ -34,8 +34,8 @@ Widget subItemTitle(BuildContext context, String textKey, {IconData iconData}) {
   );
 }
 
-Widget contactItem(BuildContext context, String text, IconData iconData,
-    {Function() onTap, String labelKey}) {
+Widget contactItem(BuildContext context, String? text, IconData iconData,
+    {Function()? onTap, String? labelKey}) {
   return Material(
     child: Padding(
       padding: const EdgeInsets.only(left: 18.0, bottom: 10, right: 18),
diff --git a/lib/pages/delivery/delivery_info.dart b/lib/pages/delivery/delivery_info.dart
index f9fecd2..0f3e423 100644
--- a/lib/pages/delivery/delivery_info.dart
+++ b/lib/pages/delivery/delivery_info.dart
@@ -22,14 +22,13 @@ import 'package:fcs/pages/widgets/local_title.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 import 'package:intl/intl.dart';
 import 'package:provider/provider.dart';
 
 final DateFormat dateFormat = DateFormat("d MMM yyyy");
 
 class DeliveryInfo extends StatefulWidget {
-  final Carton box;
+  final Carton? box;
   DeliveryInfo({this.box});
 
   @override
@@ -38,8 +37,8 @@ class DeliveryInfo extends StatefulWidget {
 
 class _DeliveryInfoState extends State<DeliveryInfo> {
   bool _isLoading = false;
-  Carton _box;
-  String _selectedCartonType;
+  late Carton _box;
+  late String _selectedCartonType;
   List<Package> _packages = [];
   List<Carton> _mixBoxes = [];
   Carton _selectedShipmentBox = new Carton();
@@ -51,16 +50,17 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
   double volumetricRatio = 0;
   double shipmentWeight = 0;
 
-  bool isMixBox;
-  bool isFromShipments;
-  bool isFromPackages;
-  bool isSmallBag;
-  bool isEdiable;
+  late bool isMixBox;
+  late bool isFromShipments;
+  late bool isFromPackages;
+  late bool isSmallBag;
+  late bool isEdiable;
 
   @override
   void initState() {
     super.initState();
-    _box = widget.box;
+    if(widget.box != null)
+    _box = widget.box!;
     _selectedCartonType = _box.cartonType;
 
     //for shipment weight
@@ -143,13 +143,13 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
       iconData: Ionicons.ios_airplane,
     );
     final fcsIDBox = DisplayText(
-      text: _box.fcsID == null ? "" : _box.fcsID,
+      text: _box.fcsID,
       labelTextKey: "box.fcs.id",
       icon: FcsIDIcon(),
     );
 
     final customerNameBox = DisplayText(
-      text: _box.userName == null ? "" : _box.userName,
+      text: _box.userName,
       labelTextKey: "box.name",
       iconData: Icons.person,
     );
@@ -173,13 +173,11 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
         children: <Widget>[
           Expanded(
               child: new Text(
-            _selectedShipmentBox.shipmentNumber == null
-                ? ""
-                : _selectedShipmentBox.shipmentNumber,
+            _selectedShipmentBox.shipmentNumber,
             style: textStyle,
           )),
           new Text(
-            _selectedShipmentBox.desc == null ? "" : _selectedShipmentBox.desc,
+            _selectedShipmentBox.desc,
             style: textStyle,
           ),
         ],
@@ -216,7 +214,7 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
     );
 
     final shipmentWeightBox = DisplayText(
-      text: shipmentWeight != null ? shipmentWeight.toStringAsFixed(0) : "",
+      text: shipmentWeight.toStringAsFixed(0) : "",
       labelTextKey: "box.shipment_weight",
       iconData: MaterialCommunityIcons.weight,
     );
@@ -302,7 +300,7 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
     });
     try {
       var deliveryModel = Provider.of<DeliveryModel>(context, listen: false);
-      await deliveryModel.deliver(widget.box);
+      await deliveryModel.deliver(this._box);
       Navigator.pop(context, true);
     } catch (e) {
       showMsgDialog(context, "Error", e.toString());
diff --git a/lib/pages/delivery/delivery_list_row.dart b/lib/pages/delivery/delivery_list_row.dart
index 16bdcac..d688e2a 100644
--- a/lib/pages/delivery/delivery_list_row.dart
+++ b/lib/pages/delivery/delivery_list_row.dart
@@ -3,14 +3,13 @@ import 'package:fcs/helpers/theme.dart';
 import 'package:fcs/pages/main/util.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 import 'package:intl/intl.dart';
 
 import 'delivery_info.dart';
 
 class DeliveryListRow extends StatelessWidget {
-  final Carton box;
-  DeliveryListRow({Key key, this.box}) : super(key: key);
+  final Carton? box;
+  DeliveryListRow({Key? key, this.box}) : super(key: key);
 
   final double dotSize = 15.0;
   final DateFormat dateFormat = new DateFormat("dd MMM yyyy");
@@ -19,10 +18,11 @@ class DeliveryListRow extends StatelessWidget {
   Widget build(BuildContext context) {
     return InkWell(
       onTap: () {
-        Navigator.push(
-          context,
-          CupertinoPageRoute(builder: (context) => DeliveryInfo(box: box)),
-        );
+        if (box != null)
+          Navigator.push(
+            context,
+            CupertinoPageRoute(builder: (context) => DeliveryInfo(box: box!)),
+          );
       },
       child: Container(
         padding: EdgeInsets.only(left: 15, right: 15),
@@ -48,7 +48,7 @@ class DeliveryListRow extends StatelessWidget {
                           Padding(
                             padding: const EdgeInsets.only(left: 8.0),
                             child: new Text(
-                              box.cartonNumber ?? "",
+                              box?.cartonNumber ?? "",
                               style: new TextStyle(
                                   fontSize: 15.0, color: Colors.black),
                             ),
@@ -56,7 +56,7 @@ class DeliveryListRow extends StatelessWidget {
                           Padding(
                             padding: const EdgeInsets.only(left: 10.0, top: 10),
                             child: new Text(
-                              box.userName ?? "",
+                              box?.userName ?? "",
                               style: new TextStyle(
                                   fontSize: 15.0, color: Colors.grey),
                             ),
@@ -72,14 +72,14 @@ class DeliveryListRow extends StatelessWidget {
               children: <Widget>[
                 Padding(
                   padding: const EdgeInsets.all(0),
-                  child: getStatus(box.status == null ? "" : box.status),
+                  child: getStatus(box?.status ?? ''),
                 ),
                 Padding(
                   padding: const EdgeInsets.only(left: 8.0, top: 5, bottom: 5),
                   child: Row(
                     children: <Widget>[
                       new Text(
-                        "${box.actualWeight?.toString() ?? ''} lb",
+                        "${box?.actualWeight.toString() ?? ''} lb",
                         style:
                             new TextStyle(fontSize: 15.0, color: Colors.grey),
                       ),
diff --git a/lib/pages/delivery_address/delivery_address_editor.dart b/lib/pages/delivery_address/delivery_address_editor.dart
index 812e0db..336adeb 100644
--- a/lib/pages/delivery_address/delivery_address_editor.dart
+++ b/lib/pages/delivery_address/delivery_address_editor.dart
@@ -7,13 +7,12 @@ import 'package:fcs/pages/widgets/input_text.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 
 class DeliveryAddressEditor extends StatefulWidget {
-  final DeliveryAddress deliveryAddress;
-  final User user;
+  final DeliveryAddress? deliveryAddress;
+  final User? user;
   DeliveryAddressEditor({this.deliveryAddress, this.user});
 
   @override
@@ -38,7 +37,7 @@ class _DeliveryAddressEditorState extends State<DeliveryAddressEditor> {
     super.initState();
     if (widget.deliveryAddress != null) {
       _isNew = false;
-      _deliveryAddress = widget.deliveryAddress;
+      _deliveryAddress = widget.deliveryAddress!;
       _nameController.text = _deliveryAddress.fullName;
       _address1Controller.text = _deliveryAddress.addressLine1;
       _address2Controller.text = _deliveryAddress.addressLine2;
@@ -198,7 +197,7 @@ class _DeliveryAddressEditorState extends State<DeliveryAddressEditor> {
       return;
     }
     if (widget.user != null) {
-      deliveryAddress.userID = widget.user.id;
+      deliveryAddress.userID = widget.user!.id;
     }
     setState(() {
       _isLoading = true;
@@ -224,7 +223,7 @@ class _DeliveryAddressEditorState extends State<DeliveryAddressEditor> {
       return;
     }
     if (widget.user != null) {
-      deliveryAddress.userID = widget.user.id;
+      deliveryAddress.userID = widget.user!.id;
     }
     setState(() {
       _isLoading = true;
@@ -255,7 +254,7 @@ class _DeliveryAddressEditorState extends State<DeliveryAddressEditor> {
       DeliveryAddressModel deliveryAddressModel =
           Provider.of<DeliveryAddressModel>(context, listen: false);
       if (widget.user != null) {
-        _deliveryAddress.userID = widget.user.id;
+        _deliveryAddress.userID = widget.user!.id;
       }
       await deliveryAddressModel.deleteDeliveryAddress(_deliveryAddress);
       Navigator.pop(context, true);
@@ -278,7 +277,7 @@ class _DeliveryAddressEditorState extends State<DeliveryAddressEditor> {
           _stateController.text != "Yangon";
     } else {
       DeliveryAddress deliveryAddress = _getPayload();
-      return widget.deliveryAddress.isChangedForEdit(deliveryAddress);
+      return this._deliveryAddress.isChangedForEdit(deliveryAddress);
     }
   }
 }
diff --git a/lib/pages/delivery_address/delivery_address_list.dart b/lib/pages/delivery_address/delivery_address_list.dart
index c8455ba..480e5b6 100644
--- a/lib/pages/delivery_address/delivery_address_list.dart
+++ b/lib/pages/delivery_address/delivery_address_list.dart
@@ -13,9 +13,9 @@ import 'model/delivery_address_model.dart';
 
 class DeliveryAddressList extends StatefulWidget {
   final bool isAdminCreation;
-  final DeliveryAddress deliveryAddress;
+  final DeliveryAddress? deliveryAddress;
   const DeliveryAddressList(
-      {Key key, this.isAdminCreation = false, this.deliveryAddress})
+      {Key? key, this.isAdminCreation = false,  this.deliveryAddress})
       : super(key: key);
   @override
   _DeliveryAddressListState createState() => _DeliveryAddressListState();
@@ -85,7 +85,7 @@ class _DeliveryAddressListState extends State<DeliveryAddressList> {
             padding: const EdgeInsets.all(10.0),
             child: Icon(Icons.check,
                 color: widget.isAdminCreation
-                    ? widget.deliveryAddress.id == deliveryAddress.id
+                    ? widget.deliveryAddress?.id == deliveryAddress.id
                         ? primaryColor
                         : Colors.black26
                     : deliveryAddress.isDefault
diff --git a/lib/pages/delivery_address/delivery_address_row.dart b/lib/pages/delivery_address/delivery_address_row.dart
index e596213..fd8f576 100644
--- a/lib/pages/delivery_address/delivery_address_row.dart
+++ b/lib/pages/delivery_address/delivery_address_row.dart
@@ -3,15 +3,14 @@ import 'package:fcs/helpers/theme.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 
 typedef SelectionCallback(DeliveryAddress deliveryAddress);
 
 class DeliveryAddressRow extends StatelessWidget {
   final DeliveryAddress deliveryAddress;
-  final SelectionCallback selectionCallback;
+  final SelectionCallback? selectionCallback;
   const DeliveryAddressRow(
-      {Key key, this.deliveryAddress, this.selectionCallback})
+      {Key? key, required this.deliveryAddress, this.selectionCallback})
       : super(key: key);
 
   @override
@@ -19,7 +18,7 @@ class DeliveryAddressRow extends StatelessWidget {
     return InkWell(
       onTap: selectionCallback == null
           ? null
-          : () => this.selectionCallback(deliveryAddress),
+          : () => this.selectionCallback!(deliveryAddress),
       child: Row(
         children: <Widget>[
           Expanded(
@@ -54,8 +53,8 @@ class DeliveryAddressRow extends StatelessWidget {
     );
   }
 
-  Widget line(BuildContext context, String text,
-      {IconData iconData, Color color, double fontSize}) {
+  Widget line(BuildContext context, String? text,
+      {IconData? iconData, Color? color, double? fontSize}) {
     return Row(
       children: [
         iconData == null
@@ -69,7 +68,7 @@ class DeliveryAddressRow extends StatelessWidget {
             context,
             text ?? "",
             fontSize: fontSize ?? 14,
-            color: color,
+            color: color ?? Colors.grey,
           ),
         ),
       ],
diff --git a/lib/pages/discount/discount_editor.dart b/lib/pages/discount/discount_editor.dart
index d967cb5..742e9c0 100644
--- a/lib/pages/discount/discount_editor.dart
+++ b/lib/pages/discount/discount_editor.dart
@@ -1,24 +1,21 @@
 import 'package:fcs/domain/entities/discount.dart';
-import 'package:fcs/domain/entities/user.dart';
 import 'package:fcs/helpers/theme.dart';
 import 'package:fcs/localization/app_translations.dart';
 import 'package:fcs/pages/discount/model/discount_model.dart';
 import 'package:fcs/pages/main/util.dart';
-import 'package:fcs/pages/rates/model/shipment_rate_model.dart';
 import 'package:fcs/pages/user_search/user_serach.dart';
 import 'package:fcs/pages/widgets/display_text.dart';
 import 'package:fcs/pages/widgets/input_text.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 import 'package:font_awesome_flutter/font_awesome_flutter.dart';
 import 'package:provider/provider.dart';
 
 class DiscountEditor extends StatefulWidget {
-  final Discount discount;
+  final Discount? discount;
 
-  const DiscountEditor({Key key, this.discount}) : super(key: key);
+  const DiscountEditor({Key? key, this.discount}) : super(key: key);
   @override
   _DiscountEditorState createState() => _DiscountEditorState();
 }
@@ -38,12 +35,12 @@ class _DiscountEditorState extends State<DiscountEditor> {
   void initState() {
     super.initState();
     if (widget.discount != null) {
-      _discount = widget.discount;
+      _discount = widget.discount!;
       _codeController.text = _discount.code;
       _amountController.text = _discount.amount.toStringAsFixed(2);
       _statusController.text = _discount.status;
-      customerName = widget.discount.customerName;
-      customerId = widget.discount.customerId;
+      customerName = _discount.customerName;
+      customerId = _discount.customerId;
     } else {
       _isNew = true;
     }
@@ -71,7 +68,7 @@ class _DiscountEditorState extends State<DiscountEditor> {
       children: <Widget>[
         Expanded(
             child: DisplayText(
-          text: customerName != null ? customerName : "",
+          text: customerName,
           labelTextKey: "discount.name",
           iconData: Feather.user,
         )),
@@ -93,7 +90,7 @@ class _DiscountEditorState extends State<DiscountEditor> {
           appBar: AppBar(
             centerTitle: true,
             title: Text(
-              AppTranslations.of(context).text("discount.form"),
+              AppTranslations.of(context)!.text("discount.form"),
             ),
             leading: new IconButton(
               icon: new Icon(CupertinoIcons.back),
@@ -162,7 +159,7 @@ class _DiscountEditorState extends State<DiscountEditor> {
       if (_isNew) {
         await discountModel.addDiscount(_discount);
       } else {
-        _discount.id = widget.discount.id;
+        _discount.id = this._discount.id;
         await discountModel.updateDiscount(_discount);
       }
       Navigator.pop(context);
@@ -186,7 +183,7 @@ class _DiscountEditorState extends State<DiscountEditor> {
     });
     try {
       var discountModel = Provider.of<DiscountModel>(context, listen: false);
-      await discountModel.deleteDiscount(widget.discount);
+      await discountModel.deleteDiscount(_discount);
       Navigator.pop(context);
     } catch (e) {
       showMsgDialog(context, "Error", e.toString());
@@ -208,7 +205,7 @@ class _DiscountEditorState extends State<DiscountEditor> {
           customerName: customerName,
           customerId: customerId,
           amount: double.parse(_amountController.text));
-      return widget.discount.isChangedForEdit(_discount);
+      return widget.discount!.isChangedForEdit(_discount);
     }
   }
 }
diff --git a/lib/pages/discount/discount_list.dart b/lib/pages/discount/discount_list.dart
index ca2845a..466f800 100644
--- a/lib/pages/discount/discount_list.dart
+++ b/lib/pages/discount/discount_list.dart
@@ -16,7 +16,7 @@ import 'discount_editor.dart';
 class DiscountList extends StatefulWidget {
   final bool selectionMode;
 
-  const DiscountList({Key key, this.selectionMode = false}) : super(key: key);
+  const DiscountList({Key? key, this.selectionMode = false}) : super(key: key);
   @override
   _DiscountListState createState() => _DiscountListState();
 }
@@ -62,7 +62,7 @@ class _DiscountListState extends State<DiscountList> {
         appBar: AppBar(
           centerTitle: true,
           title: Text(
-            AppTranslations.of(context).text("discount.title"),
+            AppTranslations.of(context)!.text("discount.title"),
           ),
           leading: new IconButton(
             icon: new Icon(CupertinoIcons.back),
diff --git a/lib/pages/discount/discount_list_row.dart b/lib/pages/discount/discount_list_row.dart
index 868905d..473b5b3 100644
--- a/lib/pages/discount/discount_list_row.dart
+++ b/lib/pages/discount/discount_list_row.dart
@@ -5,15 +5,14 @@ import 'package:fcs/pages/discount/discount_editor.dart';
 import 'package:fcs/pages/main/util.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 import 'package:intl/intl.dart';
 
 typedef OnSelect(Discount discount);
 
 class DiscountListRow extends StatelessWidget {
-  final OnSelect onSelect;
-  final Discount discount;
-  DiscountListRow({Key key, this.discount, this.onSelect}) : super(key: key);
+  final OnSelect? onSelect;
+  final Discount? discount;
+  DiscountListRow({Key? key, this.discount, this.onSelect}) : super(key: key);
 
   final DateFormat dateFormat = new DateFormat("dd MMM yyyy");
 
@@ -21,8 +20,8 @@ class DiscountListRow extends StatelessWidget {
   Widget build(BuildContext context) {
     return InkWell(
       onTap: () {
-        if (onSelect != null) {
-          onSelect(discount);
+        if (onSelect != null && discount != null) {
+        onSelect!(discount!);
         }
       },
       child: Container(
@@ -49,7 +48,7 @@ class DiscountListRow extends StatelessWidget {
                           Padding(
                             padding: const EdgeInsets.only(left: 8.0),
                             child: new Text(
-                              discount.code ?? "",
+                              discount?.code ?? "",
                               style: new TextStyle(
                                   fontSize: 15.0, color: Colors.black),
                             ),
@@ -57,7 +56,7 @@ class DiscountListRow extends StatelessWidget {
                           Padding(
                             padding: const EdgeInsets.only(left: 10.0, top: 10),
                             child: new Text(
-                              discount.customerName ?? "",
+                              discount?.customerName ?? "",
                               style: new TextStyle(
                                   fontSize: 15.0, color: Colors.grey),
                             ),
@@ -73,14 +72,14 @@ class DiscountListRow extends StatelessWidget {
               children: <Widget>[
                 Padding(
                   padding: const EdgeInsets.all(0),
-                  child: Text(discount.status),
+                  child: Text(discount?.status ?? ''),
                 ),
                 Padding(
                   padding: const EdgeInsets.only(left: 8.0, top: 5, bottom: 5),
                   child: Row(
                     children: <Widget>[
                       new Text(
-                        "${discount.amount.toStringAsFixed(2) ?? ''}",
+                        "${discount?.amount.toStringAsFixed(2) ?? ''}",
                         style:
                             new TextStyle(fontSize: 15.0, color: Colors.grey),
                       ),
diff --git a/lib/pages/discount/model/discount_model.dart b/lib/pages/discount/model/discount_model.dart
index 5a25660..445853f 100644
--- a/lib/pages/discount/model/discount_model.dart
+++ b/lib/pages/discount/model/discount_model.dart
@@ -11,13 +11,13 @@ import 'package:logging/logging.dart';
 class DiscountModel extends BaseModel {
   final log = Logger('DiscountModel');
 
-  StreamSubscription<QuerySnapshot> listener;
+  StreamSubscription<QuerySnapshot>? listener;
 
   List<Discount> _discounts = [];
   List<Discount> get discounts =>
       _selectedIndex == 1 ? _discounts : List<Discount>.from(_used.values);
 
-  Paginator _used;
+  late Paginator _used;
   bool isLoading = false;
   int _selectedIndex = 1;
   set selectedIndex(int index) {
@@ -25,14 +25,14 @@ class DiscountModel extends BaseModel {
     notifyListeners();
   }
 
-  get selectedIndex => _selectedIndex;
+  int get selectedIndex => _selectedIndex;
 
   initData() {
     _selectedIndex = 1;
     _load();
 
     if (_used != null) _used.close();
-    _used = _getUsed();
+    if (_getUsed() != null) _used = _getUsed()!;
     _used.load();
   }
 
@@ -42,7 +42,7 @@ class DiscountModel extends BaseModel {
   }
 
   _load() {
-    if (listener != null) listener.cancel();
+    if (listener != null) listener!.cancel();
     try {
       listener = Firestore.instance
           .collection("/$discounts_collection")
@@ -60,7 +60,7 @@ class DiscountModel extends BaseModel {
     }
   }
 
-  Paginator _getUsed() {
+  Paginator? _getUsed() {
     if (user == null || !user.hasFcsShipments()) return null;
 
     var pageQuery = Firestore.instance
@@ -73,7 +73,7 @@ class DiscountModel extends BaseModel {
     return paginator;
   }
 
-  Future<List<Discount>> getDiscount(String userID) async {
+  Future<List<Discount>?> getDiscount(String userID) async {
     String path = "/$discounts_collection";
     try {
       var q = Firestore.instance
@@ -113,7 +113,7 @@ class DiscountModel extends BaseModel {
 
   @override
   logout() async {
-    if (listener != null) await listener.cancel();
+    if (listener != null) await listener!.cancel();
     if (_used != null) _used.close();
 
     _discounts = [];
diff --git a/lib/pages/faq/faq_detail_page.dart b/lib/pages/faq/faq_detail_page.dart
index 8a4124f..9e7ea4b 100644
--- a/lib/pages/faq/faq_detail_page.dart
+++ b/lib/pages/faq/faq_detail_page.dart
@@ -13,14 +13,14 @@ import 'package:provider/provider.dart';
 
 class FAQDetailPage extends StatefulWidget {
   final FAQ faq;
-  const FAQDetailPage({this.faq});
+  const FAQDetailPage({required this.faq});
   @override
   _FAQDetailPageState createState() => _FAQDetailPageState();
 }
 
 class _FAQDetailPageState extends State<FAQDetailPage> {
   bool _isLoading = false;
-  FAQ faq;
+  FAQ faq = new FAQ();
 
   intState() {
     super.initState();
diff --git a/lib/pages/faq/faq_edit_page.dart b/lib/pages/faq/faq_edit_page.dart
index 73045be..a3c8ad4 100644
--- a/lib/pages/faq/faq_edit_page.dart
+++ b/lib/pages/faq/faq_edit_page.dart
@@ -10,13 +10,12 @@ import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 import 'package:provider/provider.dart';
 
 const info = "Select additional page";
 
 class FAQEditor extends StatefulWidget {
-  final FAQ faq;
+  final FAQ? faq;
   const FAQEditor({this.faq});
   @override
   _FAQEditorState createState() => _FAQEditorState();
@@ -35,20 +34,22 @@ class _FAQEditorState extends State<FAQEditor> {
   bool _isLoading = false;
   bool _isNew = false;
   String _pageLink = info;
+  FAQ _faq = new FAQ();
 
   @override
   void initState() {
     super.initState();
     _isNew = widget.faq == null;
     if (widget.faq != null) {
-      _sn.text = widget.faq.sn.toString();
-      _engQ.text = widget.faq.questionEng;
-      _mmQ.text = widget.faq.questionMm;
-      _engA.text = widget.faq.answerEng;
-      _mmA.text = widget.faq.answerMm;
-      _pageLabelEng.text = widget.faq.pageLinkLabelEng;
-      _pageLabelMm.text = widget.faq.pageLinkLabelMm;
-      _pageLink = widget.faq.pageLink;
+      _faq = widget.faq!;
+      _sn.text = _faq.sn.toString();
+      _engQ.text = _faq.questionEng;
+      _mmQ.text = _faq.questionMm;
+      _engA.text = _faq.answerEng;
+      _mmA.text = _faq.answerMm;
+      _pageLabelEng.text = _faq.pageLinkLabelEng;
+      _pageLabelMm.text = _faq.pageLinkLabelMm;
+      _pageLink = _faq.pageLink;
     }
   }
 
@@ -89,7 +90,8 @@ class _FAQEditorState extends State<FAQEditor> {
         height: 2,
         color: primaryColor,
       ),
-      onChanged: (String newValue) {
+      onChanged: (String? newValue) {
+        if(newValue != null)
         setState(() {
           _pageLink = newValue;
         });
@@ -211,7 +213,7 @@ class _FAQEditorState extends State<FAQEditor> {
       if (_isNew) {
         await faqModel.addFAQ(_faq);
       } else {
-        _faq.id = widget.faq.id;
+        _faq.id = this._faq.id;
         await faqModel.updateFAQ(_faq);
       }
       Navigator.pop(context);
@@ -234,7 +236,7 @@ class _FAQEditorState extends State<FAQEditor> {
     });
     try {
       FAQModel faqModel = Provider.of<FAQModel>(context, listen: false);
-      await faqModel.deleteFAQ(widget.faq);
+      await faqModel.deleteFAQ(this._faq);
       Navigator.pop(context);
     } catch (e) {
       showMsgDialog(context, "Error", e.toString());
diff --git a/lib/pages/faq/faq_list_page.dart b/lib/pages/faq/faq_list_page.dart
index 2c5ae2d..1e8bc36 100644
--- a/lib/pages/faq/faq_list_page.dart
+++ b/lib/pages/faq/faq_list_page.dart
@@ -1,14 +1,12 @@
 import 'package:fcs/domain/constants.dart';
 import 'package:fcs/domain/entities/faq.dart';
 import 'package:fcs/helpers/theme.dart';
-import 'package:fcs/localization/app_translations.dart';
 import 'package:fcs/pages/buying_instruction/buying_online.dart';
 import 'package:fcs/pages/faq/faq_edit_page.dart';
 import 'package:fcs/pages/main/model/language_model.dart';
 import 'package:fcs/pages/main/model/main_model.dart';
 import 'package:fcs/pages/payment_methods/payment_method_page.dart';
 import 'package:fcs/pages/rates/shipment_rates.dart';
-import 'package:fcs/pages/widgets/bottom_up_page_route.dart';
 import 'package:fcs/pages/widgets/fcs_expansion_tile.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:flutter/cupertino.dart';
@@ -26,8 +24,8 @@ class FAQListPage extends StatefulWidget {
 
 class _FAQListPageState extends State<FAQListPage>
     with SingleTickerProviderStateMixin {
-  AnimationController _controller;
-  Animation<double> _iconTurns;
+  AnimationController? _controller;
+  Animation<double>? _iconTurns;
 
   @override
   void initState() {
@@ -35,7 +33,7 @@ class _FAQListPageState extends State<FAQListPage>
     _controller = AnimationController(duration: _kExpand, vsync: this);
     var _halfTween = Tween<double>(begin: 0.0, end: 0.5);
     var _easeInTween = CurveTween(curve: Curves.easeIn);
-    _iconTurns = _controller.drive(_halfTween.chain(_easeInTween));
+    _iconTurns = _controller?.drive(_halfTween.chain(_easeInTween));
   }
 
   @override
@@ -139,7 +137,7 @@ class _FAQListPageState extends State<FAQListPage>
     );
   }
 
-  Widget _pageLink(String linkPage, String text) {
+  Widget _pageLink(String? linkPage, String? text) {
     return linkPage == null || linkPage == "" || text == null || text == ""
         ? Container()
         : Row(
diff --git a/lib/pages/main/initial_language_selection.dart b/lib/pages/main/initial_language_selection.dart
index 35389db..0253db3 100644
--- a/lib/pages/main/initial_language_selection.dart
+++ b/lib/pages/main/initial_language_selection.dart
@@ -3,7 +3,6 @@ import 'package:fcs/helpers/theme.dart';
 import 'package:fcs/localization/transalation.dart';
 import 'package:fcs/pages/main/model/language_model.dart';
 import 'package:fcs/pages/main/model/main_model.dart';
-import 'package:fcs/pages/signin/signin_page.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/material.dart';
@@ -27,9 +26,9 @@ class _InitialLanguageSelectionPageState
     languagesList[1]: languageCodesList[1],
   };
 
-  late String selectedLanguage;
+   String selectedLanguage = 'en';
   late int selectedIndex;
-  bool _isLoading = false;
+   bool _isLoading = false;
 
   @override
   void initState() {
@@ -102,8 +101,8 @@ class _InitialLanguageSelectionPageState
                                   ? BoxDecoration()
                                   : BoxDecoration(
                                       border: Border(
-                                        bottom: BorderSide(
-                                            color: Colors.grey.shade300),
+                                        bottom:
+                                            BorderSide(color: Colors.grey.shade300),
                                       ),
                                     ),
                               child: ListTile(
diff --git a/lib/pages/profile/profile_currency_edit.dart b/lib/pages/profile/profile_currency_edit.dart
index 6bf1c6f..f1d3b71 100644
--- a/lib/pages/profile/profile_currency_edit.dart
+++ b/lib/pages/profile/profile_currency_edit.dart
@@ -1,6 +1,4 @@
 import 'package:fcs/helpers/theme.dart';
-import 'package:fcs/localization/app_translations.dart';
-import 'package:fcs/pages/main/model/language_model.dart';
 import 'package:fcs/pages/main/model/main_model.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:fcs/pages/widgets/progress.dart';
@@ -77,6 +75,7 @@ class _ProfileCurrencyEditState extends State<ProfileCurrencyEdit> {
                   value: Currency.USD,
                   groupValue: _currency,
                   onChanged: (Currency? value) {
+                    if(value != null)
                     setState(() {
                       _currency = value!;
                     });
@@ -95,6 +94,7 @@ class _ProfileCurrencyEditState extends State<ProfileCurrencyEdit> {
                   value: Currency.MMK,
                   groupValue: _currency,
                   onChanged: (Currency? value) {
+                    if(value != null)
                     setState(() {
                       _currency = value!;
                     });
diff --git a/lib/pages/profile/profile_edit.dart b/lib/pages/profile/profile_edit.dart
index a4ab671..db9a610 100644
--- a/lib/pages/profile/profile_edit.dart
+++ b/lib/pages/profile/profile_edit.dart
@@ -39,7 +39,7 @@ class _ProfileEditState extends State<ProfileEdit> {
           cursorColor: primaryColor,
           style: textStyle,
           decoration: new InputDecoration(
-            labelText: AppTranslations.of(context).text("profile.name"),
+            labelText: AppTranslations.of(context)!.text("profile.name"),
             labelStyle: languageModel.isEng ? labelStyle : labelStyleMM,
             icon: Icon(
               Icons.person,
diff --git a/lib/pages/profile/profile_page.dart b/lib/pages/profile/profile_page.dart
index 67395f9..00668cb 100644
--- a/lib/pages/profile/profile_page.dart
+++ b/lib/pages/profile/profile_page.dart
@@ -1,9 +1,7 @@
 import 'package:fcs/domain/entities/user.dart';
-import 'package:fcs/domain/vo/delivery_address.dart';
 import 'package:fcs/domain/vo/privilege.dart';
 import 'package:fcs/localization/transalation.dart';
 import 'package:fcs/pages/delivery_address/delivery_address_list.dart';
-import 'package:fcs/pages/delivery_address/delivery_address_row.dart';
 import 'package:fcs/pages/delivery_address/model/delivery_address_model.dart';
 import 'package:fcs/pages/main/model/language_model.dart';
 import 'package:fcs/pages/main/model/main_model.dart';
@@ -11,7 +9,6 @@ import 'package:fcs/pages/main/util.dart';
 import 'package:fcs/pages/profile/profile_currency_edit.dart';
 import 'package:fcs/pages/profile/profile_edit.dart';
 import 'package:fcs/pages/staff/model/staff_model.dart';
-import 'package:fcs/pages/widgets/bottom_up_page_route.dart';
 import 'package:fcs/pages/widgets/defalut_delivery_address.dart';
 import 'package:fcs/pages/widgets/display_text.dart';
 import 'package:fcs/pages/widgets/fcs_id_icon.dart';
@@ -20,7 +17,6 @@ import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 import 'package:provider/provider.dart';
 
 import '../../helpers/theme.dart';
@@ -35,7 +31,7 @@ class Profile extends StatefulWidget {
 class _ProfileState extends State<Profile> {
   GlobalKey key = GlobalKey();
   bool _isLoading = false;
-  String selectedLanguage;
+   String? selectedLanguage ;
   TextEditingController bizNameController = new TextEditingController();
 
   static final List<String> languagesList = Translation().supportedLanguages;
diff --git a/lib/pages/rates/cargo_editor.dart b/lib/pages/rates/cargo_editor.dart
index d084754..30224bf 100644
--- a/lib/pages/rates/cargo_editor.dart
+++ b/lib/pages/rates/cargo_editor.dart
@@ -11,7 +11,7 @@ import 'package:provider/provider.dart';
 import 'model/shipment_rate_model.dart';
 
 class CargoEditor extends StatefulWidget {
-  final CargoType cargo;
+  final CargoType? cargo;
   CargoEditor({this.cargo});
 
   @override
@@ -23,14 +23,14 @@ class _CargoEditorState extends State<CargoEditor> {
   TextEditingController _rateController = new TextEditingController();
 
   bool _isLoading = false;
-  CargoType _cargo;
+  late CargoType _cargo;
   bool _isNew = false;
 
   @override
   void initState() {
     super.initState();
     if (widget.cargo != null) {
-      _cargo = widget.cargo;
+      _cargo = widget.cargo!;
       _descController.text = _cargo.name;
       _rateController.text = _cargo.rate.toStringAsFixed(2);
     } else {
@@ -71,7 +71,7 @@ class _CargoEditorState extends State<CargoEditor> {
             },
           ),
           backgroundColor: primaryColor,
-          title: Text(AppTranslations.of(context).text("cargo.form.title")),
+          title: Text(AppTranslations.of(context)!.text("cargo.form.title")),
           actions: [
             IconButton(
               icon: Icon(Icons.delete),
@@ -114,7 +114,7 @@ class _CargoEditorState extends State<CargoEditor> {
       if (_isNew) {
         await shipmentRateModel.addCargoType(_cargo);
       } else {
-        _cargo.id = widget.cargo.id;
+        _cargo.id = this._cargo.id;
         await shipmentRateModel.updateCargoType(_cargo);
       }
       Navigator.pop(context);
@@ -138,7 +138,7 @@ class _CargoEditorState extends State<CargoEditor> {
     try {
       var shipmentRateModel =
           Provider.of<ShipmentRateModel>(context, listen: false);
-      await shipmentRateModel.deleteCargoType(widget.cargo.id);
+      await shipmentRateModel.deleteCargoType(this._cargo.id);
       Navigator.pop(context);
     } catch (e) {
       showMsgDialog(context, "Error", e.toString());
@@ -155,7 +155,7 @@ class _CargoEditorState extends State<CargoEditor> {
     } else {
       CargoType _cargo = CargoType(
           name: _descController.text, rate: double.parse(_rateController.text));
-      return widget.cargo.isChangedForEdit(_cargo);
+      return this._cargo.isChangedForEdit(_cargo);
     }
   }
 }
diff --git a/lib/pages/rates/cargo_type_list.dart b/lib/pages/rates/cargo_type_list.dart
index 1e766c3..aa5ac42 100644
--- a/lib/pages/rates/cargo_type_list.dart
+++ b/lib/pages/rates/cargo_type_list.dart
@@ -10,7 +10,7 @@ import 'cargo_editor.dart';
 import 'model/shipment_rate_model.dart';
 
 class CargoTypeList extends StatefulWidget {
-  const CargoTypeList({Key key}) : super(key: key);
+  const CargoTypeList({Key? key}) : super(key: key);
   @override
   _CargoTypeListState createState() => _CargoTypeListState();
 }
diff --git a/lib/pages/rates/custom_editor.dart b/lib/pages/rates/custom_editor.dart
index 018804d..17444e2 100644
--- a/lib/pages/rates/custom_editor.dart
+++ b/lib/pages/rates/custom_editor.dart
@@ -12,7 +12,7 @@ import 'package:provider/provider.dart';
 import 'model/shipment_rate_model.dart';
 
 class CustomEditor extends StatefulWidget {
-  final CargoType custom;
+  final CargoType? custom;
   CustomEditor({this.custom});
 
   @override
@@ -32,7 +32,7 @@ class _CustomEditorState extends State<CustomEditor> {
   void initState() {
     super.initState();
     if (widget.custom != null) {
-      _custom = widget.custom;
+      _custom = widget.custom!;
       _productController.text = _custom.name;
       _feeController.text = _custom.customDutyFee.toStringAsFixed(2);
       _shipmentRateController.text =
@@ -83,7 +83,7 @@ class _CustomEditorState extends State<CustomEditor> {
           ),
           backgroundColor: primaryColor,
           title:
-              Text(AppTranslations.of(context).text("rate.custom.form.title")),
+              Text(AppTranslations.of(context)!.text("rate.custom.form.title")),
           actions: [
             IconButton(
               icon: Icon(Icons.delete),
@@ -129,7 +129,7 @@ class _CustomEditorState extends State<CustomEditor> {
       if (_isNew) {
         await shipmentRateModel.addCustomDuty(_customduty);
       } else {
-        _customduty.id = widget.custom.id;
+        _customduty.id = this._custom.id;
         await shipmentRateModel.updateCustomDuty(_customduty);
       }
       Navigator.pop(context);
@@ -154,7 +154,7 @@ class _CustomEditorState extends State<CustomEditor> {
     try {
       var shipmentRateModel =
           Provider.of<ShipmentRateModel>(context, listen: false);
-      await shipmentRateModel.deleteCustomDuty(widget.custom.id);
+      await shipmentRateModel.deleteCustomDuty(this._custom.id);
       Navigator.pop(context);
     } catch (e) {
       showMsgDialog(context, "Error", e.toString());
@@ -175,7 +175,7 @@ class _CustomEditorState extends State<CustomEditor> {
           name: _productController.text,
           customDutyFee: double.parse(_feeController.text),
           rate: double.parse(_shipmentRateController.text));
-      return widget.custom.isChangedForEditCustomDuty(_customduty);
+      return this._custom.isChangedForEditCustomDuty(_customduty);
     }
   }
 }
diff --git a/lib/pages/rates/custom_list.dart b/lib/pages/rates/custom_list.dart
index bbff27c..8512b4a 100644
--- a/lib/pages/rates/custom_list.dart
+++ b/lib/pages/rates/custom_list.dart
@@ -1,11 +1,6 @@
 import 'package:fcs/domain/entities/cargo_type.dart';
-import 'package:fcs/domain/entities/custom_duty.dart';
-import 'package:fcs/domain/vo/delivery_address.dart';
 import 'package:fcs/helpers/theme.dart';
-import 'package:fcs/pages/delivery_address/delivery_address_editor.dart';
-import 'package:fcs/pages/main/util.dart';
 import 'package:fcs/pages/rates/custom_editor.dart';
-import 'package:fcs/pages/widgets/bottom_up_page_route.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
@@ -14,8 +9,8 @@ import 'package:provider/provider.dart';
 import 'model/shipment_rate_model.dart';
 
 class CustomList extends StatefulWidget {
-  final bool selected;
-  const CustomList({Key key, this.selected}) : super(key: key);
+  final bool? selected;
+  const CustomList({Key? key, this.selected}) : super(key: key);
   @override
   _CustomListState createState() => _CustomListState();
 }
@@ -28,7 +23,7 @@ class _CustomListState extends State<CustomList> {
   void initState() {
     super.initState();
     if (widget.selected != null) {
-      _selected = widget.selected;
+      _selected = widget.selected!;
     }
   }
 
diff --git a/lib/pages/rates/custom_row.dart b/lib/pages/rates/custom_row.dart
index 87a1a89..ae14714 100644
--- a/lib/pages/rates/custom_row.dart
+++ b/lib/pages/rates/custom_row.dart
@@ -4,14 +4,13 @@ import 'package:fcs/helpers/theme.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 
 typedef SelectionCallback(CustomDuty custom);
 
 class CustomRow extends StatelessWidget {
   final CustomDuty custom;
-  final SelectionCallback selectionCallback;
-  const CustomRow({Key key, this.custom, this.selectionCallback})
+  final SelectionCallback? selectionCallback;
+  const CustomRow({Key? key, required this.custom, this.selectionCallback})
       : super(key: key);
 
   @override
@@ -19,7 +18,7 @@ class CustomRow extends StatelessWidget {
     return InkWell(
       onTap: selectionCallback == null
           ? null
-          : () => this.selectionCallback(custom),
+          : () => this.selectionCallback!(custom),
       child: Row(
         children: <Widget>[
           Expanded(
@@ -40,8 +39,8 @@ class CustomRow extends StatelessWidget {
     );
   }
 
-  Widget line(BuildContext context, String text,
-      {IconData iconData, Color color, double fontSize}) {
+  Widget line(BuildContext context, String? text,
+      {IconData? iconData, Color? color, double? fontSize}) {
     return Row(
       children: [
         iconData == null
@@ -55,7 +54,7 @@ class CustomRow extends StatelessWidget {
             context,
             text ?? "",
             fontSize: fontSize ?? 14,
-            color: color,
+            color: color ?? Colors.grey,
           ),
         ),
       ],
diff --git a/lib/pages/rates/discount_by weight_list.dart b/lib/pages/rates/discount_by weight_list.dart
index 73b7467..ad54af2 100644
--- a/lib/pages/rates/discount_by weight_list.dart	
+++ b/lib/pages/rates/discount_by weight_list.dart	
@@ -1,24 +1,16 @@
-import 'package:fcs/domain/entities/custom_duty.dart';
-import 'package:fcs/domain/entities/discount.dart';
 import 'package:fcs/domain/entities/discount_by_weight.dart';
-import 'package:fcs/domain/vo/delivery_address.dart';
 import 'package:fcs/helpers/theme.dart';
-import 'package:fcs/pages/delivery_address/delivery_address_editor.dart';
-import 'package:fcs/pages/main/util.dart';
-import 'package:fcs/pages/rates/custom_editor.dart';
 import 'package:fcs/pages/rates/discount_by_weight_editor.dart';
-import 'package:fcs/pages/widgets/bottom_up_page_route.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 
-import 'custom_row.dart';
 import 'model/shipment_rate_model.dart';
 
 class DiscountByWeightList extends StatefulWidget {
-  const DiscountByWeightList({Key key}) : super(key: key);
+  const DiscountByWeightList({Key? key}) : super(key: key);
   @override
   _DiscountByWeightListState createState() => _DiscountByWeightListState();
 }
diff --git a/lib/pages/rates/discount_by_weight_editor.dart b/lib/pages/rates/discount_by_weight_editor.dart
index 973d156..7227298 100644
--- a/lib/pages/rates/discount_by_weight_editor.dart
+++ b/lib/pages/rates/discount_by_weight_editor.dart
@@ -11,7 +11,7 @@ import 'package:font_awesome_flutter/font_awesome_flutter.dart';
 import 'package:provider/provider.dart';
 
 class DiscountByWeightEditor extends StatefulWidget {
-  final DiscountByWeight discountByWeight;
+  final DiscountByWeight? discountByWeight;
   DiscountByWeightEditor({this.discountByWeight});
 
   @override
@@ -23,14 +23,14 @@ class _DiscountByWeightEditorState extends State<DiscountByWeightEditor> {
   TextEditingController _discountController = new TextEditingController();
 
   bool _isLoading = false;
-  bool _isNew;
+  bool _isNew = false;
   DiscountByWeight _discountByWeight = new DiscountByWeight();
 
   @override
   void initState() {
     super.initState();
     if (widget.discountByWeight != null) {
-      _discountByWeight = widget.discountByWeight;
+      _discountByWeight = widget.discountByWeight!;
       _weightController.text = _discountByWeight.weight.toStringAsFixed(2);
       _discountController.text = _discountByWeight.discount.toString();
       _isNew = false;
@@ -73,7 +73,7 @@ class _DiscountByWeightEditorState extends State<DiscountByWeightEditor> {
             },
           ),
           backgroundColor: primaryColor,
-          title: Text(AppTranslations.of(context).text("discount.new")),
+          title: Text(AppTranslations.of(context)!.text("discount.new")),
           actions: [
             IconButton(
               icon: Icon(Icons.delete),
@@ -117,7 +117,7 @@ class _DiscountByWeightEditorState extends State<DiscountByWeightEditor> {
       if (_isNew) {
         await shipmentRateModel.addDiscountByWeight(_discount);
       } else {
-        _discount.id = widget.discountByWeight.id;
+        _discount.id = this._discountByWeight.id;
         await shipmentRateModel.updateDiscountByWeight(_discount);
       }
       Navigator.pop(context);
@@ -143,7 +143,7 @@ class _DiscountByWeightEditorState extends State<DiscountByWeightEditor> {
       var shipmentRateModel =
           Provider.of<ShipmentRateModel>(context, listen: false);
       await shipmentRateModel
-          .deleteDiscountByWeight(widget.discountByWeight.id);
+          .deleteDiscountByWeight(this._discountByWeight.id);
       Navigator.pop(context);
     } catch (e) {
       showMsgDialog(context, "Error", e.toString());
@@ -161,7 +161,7 @@ class _DiscountByWeightEditorState extends State<DiscountByWeightEditor> {
       DiscountByWeight _discount = DiscountByWeight(
           weight: double.parse(_weightController.text),
           discount: double.parse(_discountController.text));
-      return widget.discountByWeight.isChangedForEdit(_discount);
+      return this._discountByWeight.isChangedForEdit(_discount);
     }
   }
 }
diff --git a/lib/pages/rates/shipment_rates_calculate.dart b/lib/pages/rates/shipment_rates_calculate.dart
index 8d21d54..e0526fd 100644
--- a/lib/pages/rates/shipment_rates_calculate.dart
+++ b/lib/pages/rates/shipment_rates_calculate.dart
@@ -2,7 +2,6 @@ import 'package:fcs/domain/entities/carton.dart';
 import 'package:fcs/domain/entities/cargo_type.dart';
 import 'package:fcs/domain/entities/rate.dart';
 import 'package:fcs/helpers/theme.dart';
-import 'package:fcs/pages/main/util.dart';
 import 'package:fcs/pages/rates/model/shipment_rate_model.dart';
 import 'package:fcs/pages/widgets/display_text.dart';
 import 'package:fcs/pages/widgets/input_text.dart';
@@ -12,7 +11,6 @@ import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
 import 'package:provider/provider.dart';
 
 class ShipmentRatesCal extends StatefulWidget {
@@ -24,7 +22,7 @@ class ShipmentRatesCal extends StatefulWidget {
 
 class _ShipmentRatesCalState extends State<ShipmentRatesCal> {
   bool _isLoading = false;
-  CargoType _cargoType;
+  late CargoType _cargoType;
   TextEditingController _widthController = new TextEditingController();
   TextEditingController _heightController = new TextEditingController();
   TextEditingController _lengthController = new TextEditingController();
diff --git a/lib/pages/rates/shipment_rates_edit.dart b/lib/pages/rates/shipment_rates_edit.dart
index b85f5aa..15149ba 100644
--- a/lib/pages/rates/shipment_rates_edit.dart
+++ b/lib/pages/rates/shipment_rates_edit.dart
@@ -1,12 +1,8 @@
-import 'package:fcs/domain/entities/cargo_type.dart';
-import 'package:fcs/domain/entities/custom_duty.dart';
-import 'package:fcs/domain/entities/discount_by_weight.dart';
 import 'package:fcs/domain/entities/rate.dart';
 import 'package:fcs/helpers/theme.dart';
 import 'package:fcs/localization/app_translations.dart';
 import 'package:fcs/pages/rates/model/shipment_rate_model.dart';
 import 'package:fcs/pages/widgets/input_text.dart';
-import 'package:fcs/pages/widgets/my_data_table.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
@@ -14,8 +10,6 @@ import 'package:font_awesome_flutter/font_awesome_flutter.dart';
 import 'package:provider/provider.dart';
 
 import '../main/util.dart';
-import 'cargo_editor.dart';
-import 'custom_editor.dart';
 
 class ShipmentRatesEdit extends StatefulWidget {
   ShipmentRatesEdit();
@@ -32,7 +26,7 @@ class _ShipmentRatesEditState extends State<ShipmentRatesEdit> {
   TextEditingController _diffDiscountWeight = new TextEditingController();
   TextEditingController _diffWeightRate = new TextEditingController();
 
-  Rate rate;
+  late Rate rate;
 
   @override
   void initState() {
@@ -99,7 +93,7 @@ class _ShipmentRatesEditState extends State<ShipmentRatesEdit> {
             },
           ),
           backgroundColor: primaryColor,
-          title: Text(AppTranslations.of(context).text("rate.edit.title")),
+          title: Text(AppTranslations.of(context)!.text("rate.edit.title")),
         ),
         body: Container(
           padding: EdgeInsets.all(18),
diff --git a/lib/pages/signin/invitation_request_page.dart b/lib/pages/signin/invitation_request_page.dart
index 5e94f6d..8099283 100644
--- a/lib/pages/signin/invitation_request_page.dart
+++ b/lib/pages/signin/invitation_request_page.dart
@@ -16,7 +16,7 @@ class RequestInvitationPage extends StatefulWidget {
 
 class _RequestInvitationPageState extends State<RequestInvitationPage> {
   bool _isLoading = false;
-  TextEditingController nameCtl;
+  TextEditingController nameCtl = new TextEditingController();
 
   @override
   void initState() {
diff --git a/lib/pages/signin/signin_page.dart b/lib/pages/signin/signin_page.dart
index 3e3470d..8938d3b 100644
--- a/lib/pages/signin/signin_page.dart
+++ b/lib/pages/signin/signin_page.dart
@@ -3,7 +3,6 @@ import 'package:fcs/domain/entities/auth_result.dart';
 import 'package:fcs/domain/entities/auth_status.dart';
 import 'package:fcs/pages/main/model/main_model.dart';
 import 'package:fcs/pages/signin/signin_logic.dart';
-import 'package:fcs/pages/widgets/bottom_up_page_route.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
 import 'package:fcs/pages/widgets/progress.dart';
 import 'package:flutter/cupertino.dart';
@@ -23,9 +22,9 @@ class SigninPage extends StatefulWidget {
 
 class _SigninPageState extends State<SigninPage> {
   bool _isLoading = false;
-  String dialCode;
+  late String dialCode;
 
-  TextEditingController phonenumberCtl;
+  TextEditingController phonenumberCtl = new TextEditingController();
 
   @override
   void initState() {
@@ -82,7 +81,7 @@ class _SigninPageState extends State<SigninPage> {
           children: <Widget>[
             Container(
               decoration: BoxDecoration(
-                  border: Border.all(color: Colors.grey[400], width: 1),
+                  border: Border.all(color: Colors.grey.shade400, width: 1),
                   borderRadius: BorderRadius.all(Radius.circular(12.0))),
               child: CountryCodePicker(
                 onChanged: _countryChange,
@@ -152,7 +151,7 @@ class _SigninPageState extends State<SigninPage> {
 
   _countryChange(CountryCode countryCode) {
     setState(() {
-      dialCode = countryCode.dialCode;
+      dialCode = countryCode.dialCode ?? '+95';
     });
   }
 
diff --git a/lib/pages/signin/signup_page.dart b/lib/pages/signin/signup_page.dart
index 4f96e6e..04a08c8 100644
--- a/lib/pages/signin/signup_page.dart
+++ b/lib/pages/signin/signup_page.dart
@@ -17,7 +17,7 @@ class SignupPage extends StatefulWidget {
 
 class _SignupPageState extends State<SignupPage> {
   bool _isLoading = false;
-  TextEditingController nameCtl;
+  TextEditingController nameCtl = new TextEditingController();
 
   @override
   void initState() {
diff --git a/lib/pages/signin/sms_code_page.dart b/lib/pages/signin/sms_code_page.dart
index dfe677c..73ef48e 100644
--- a/lib/pages/signin/sms_code_page.dart
+++ b/lib/pages/signin/sms_code_page.dart
@@ -18,18 +18,19 @@ const resend_count_sec = 30;
 
 class SmsCodePage extends StatefulWidget {
   final String phoneNumber;
-  const SmsCodePage({Key key, this.phoneNumber}) : super(key: key);
+  const SmsCodePage({Key? key, required this.phoneNumber}) : super(key: key);
   @override
   _SmsCodePageState createState() => _SmsCodePageState();
 }
 
 class _SmsCodePageState extends State<SmsCodePage> {
   bool _isLoading = false;
-  String pin;
-  bool allNumberEntered;
-  Timer _timer;
-  int _start = resend_count_sec;
   bool canResend = false;
+  int _start = resend_count_sec;
+
+  late String pin;
+  late bool allNumberEntered;
+  late Timer _timer;
 
   @override
   void initState() {
@@ -116,7 +117,7 @@ class _SmsCodePageState extends State<SmsCodePage> {
                       pinLength: 6,
                       decoration: BoxLooseDecoration(
                           strokeColorBuilder: PinListenColorBuilder(
-                              primaryColor, Colors.grey[400])),
+                              primaryColor, Colors.grey.shade400)),
                       textInputAction: TextInputAction.done,
                       autoFocus: true,
                       onChanged: _pinChange,
@@ -133,13 +134,13 @@ class _SmsCodePageState extends State<SmsCodePage> {
                           child: LocalText(context, 'sms.resend',
                               fontSize: 16,
                               color:
-                                  canResend ? primaryColor : Colors.grey[400]),
+                                  canResend ? primaryColor : Colors.grey.shade400),
                           shape: RoundedRectangleBorder(
                               borderRadius: BorderRadius.circular(10.0),
                               side: BorderSide(
                                   color: canResend
                                       ? primaryColor
-                                      : Colors.grey[400])),
+                                      : Colors.grey.shade400)),
                         ),
                         InkWell(
                           onTap: allNumberEntered ? _verify : null,