Mobile_POS_App/lib/main.dart

import 'package:Mobile_POS/screens/add_to_cart_screen.dart';
import 'package:Mobile_POS/screens/dashboard_screen.dart';
import './screens/login_screen.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.deepOrange,
        scaffoldBackgroundColor:  Colors.white,
      ),
      debugShowCheckedModeBanner: false,
      // home: MyHomePage(),
      home: LoginScreen(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin {
  int _currentIndex = 0;

  TabController controller;

  @override
  void initState(){
    super.initState();
    controller = TabController(length: 2, vsync: this);
  }

  @override
  void dispose(){
    controller.dispose();
    super.dispose();
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(
            'Simon\'s BBQ Team',
          ),
        bottom: TabBar(
          controller: controller,
          tabs: [
            Tab(
              icon: Icon(Icons.all_inbox),
              child: Text('Item'),
            ),
            Tab(
              icon: Icon(Icons.add_shopping_cart),
              child: Text('Add to Cart'),
            ),
          ],
        ),
      ),
      endDrawer: Drawer(
        child: Column(
          children: [
            Container(
              width: double.infinity,
              padding: EdgeInsets.symmetric(vertical: 20),
              color: Colors.deepOrange,
              child: Column(
                children: [
                  Icon(
                    Icons.food_bank_outlined,
                    size: 200,
                    color: Colors.white,
                  ),
                  Text(
                      'Simon\'s BBQ Team',
                    style: TextStyle(
                      fontSize: 20,
                      fontWeight: FontWeight.w500,
                      color: Colors.white,
                    ),
                  ),
                ],
              ),
            ),
            ListTile(
              onTap: (){},
              leading: Icon(Icons.person_rounded),
              title: Text(
                  'Profile',
                style: TextStyle(
                  fontSize: 18,
                ),
              ),
            ),
            ListTile(
              onTap: (){},
              leading: Icon(Icons.account_box_outlined),
              title: Text(
                'About Us',
                style: TextStyle(
                  fontSize: 18,
                ),
              ),
            ),
            ListTile(
              onTap: (){},
              leading: Icon(Icons.contact_page),
              title: Text(
                'Contact Us',
                style: TextStyle(
                  fontSize: 18,
                ),
              ),
            ),
            ListTile(
              onTap: (){},
              leading: Icon(Icons.help_outline_rounded),
              title: Text(
                'Help',
                style: TextStyle(
                  fontSize: 18,
                ),
              ),
            ),
            ListTile(
              onTap: (){},
              leading: Icon(Icons.exit_to_app),
              title: Text(
                'Exit',
                style: TextStyle(
                  fontSize: 18,
                ),
              ),
            ),
          ],
        ),
      ),
      body: TabBarView(
        controller: controller,
        children: [
          DashboardScreen(),
          AddToCartScreen(),
        ],
      ),
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _currentIndex,
        type: BottomNavigationBarType.fixed,
        backgroundColor: Colors.blueGrey[100],
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.all_inbox_outlined),
            title: Text('All Items'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.food_bank_outlined),
            title: Text('Food'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.hourglass_bottom),
            title: Text('Alcohol'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.local_drink),
            title: Text('Cold Drinks'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.no_drinks),
            title: Text('Hot Drinks'),
          ),
        ],
        onTap: (index){
          setState(() {
            _currentIndex = index;
          });
        },
      ),
    );
  }
}