How To Add Total Price In Product Using Flutter Android App

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: OrderPage(),
    );
  }
}

class cartConstant {
  static int packageCount;
  static List<int> list;
}

class OrderPage extends StatefulWidget {
  @override
  _OrderPageState createState() => _OrderPageState();
}

class _OrderPageState extends State<OrderPage> {
  int data = 3;

  void refresh() {
    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      appBar: AppBar(
        automaticallyImplyLeading: true,
        iconTheme: IconThemeData(
          color: Colors.black54, 
        ),
        backgroundColor: Colors.orange[800],
        elevation: 1,
        title: Text(
          "Order History",
          style: TextStyle(color: Colors.white),
        ),
        centerTitle: true,
      ),
      body: Container(
        child: FutureBuilder(
          builder: (context, snapshot) {
            return ListView.builder(
              physics: ClampingScrollPhysics(),
              shrinkWrap: true,
              itemCount: data,
              itemBuilder: (BuildContext context, int index) {
                return CartListView(refresh);
              },
              padding: EdgeInsets.symmetric(horizontal: 10.0),
              scrollDirection: Axis.vertical,
            );
          },
        ),
      ),
      bottomNavigationBar: _buildTotalContainer(),
    );
  }

  Widget _buildTotalContainer() {
    return Container(
      height: 200.0,
      padding: EdgeInsets.only(left: 5.0, right: 5.0,),
      child: Column(
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.only(top: 30),
            child: Row(
              mainAxisSize: MainAxisSize.max,
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: <Widget>[
                Text(
                  "Subtotal",
                  style: TextStyle(
                      color: Colors.black54,
                      fontSize: 14.0,
                      fontWeight: FontWeight.bold),
                ),
                Text(
                  cartConstant.packageCount.toString(),
                  style: TextStyle(
                      color: Colors.orange[800],
                      fontSize: 16.0,
                      fontWeight: FontWeight.bold),
                ),
              ],
            ),
          ),
          SizedBox(height: 15),
          Row(
            mainAxisSize: MainAxisSize.max,
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: <Widget>[
              Text(
                "Discount",
                style: TextStyle(
                    color: Colors.black54,
                    fontSize: 14.0,
                    fontWeight: FontWeight.bold),
              ),
              Text(
                "0.0",
                style: TextStyle(
                    color: Colors.orange[800],
                    fontWeight: FontWeight.bold),
              ),
            ],
          ),
          SizedBox(height: 15),
          Divider(height: 2.0,),
          Row(
            mainAxisSize: MainAxisSize.max,
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: <Widget>[
              Text(
                "Cart Total",
                style: TextStyle(
                    color: Colors.black54,
                    fontSize: 14.0,
                    fontWeight: FontWeight.bold),
              ),
              Text(
                "8000",
                style: TextStyle(
                    color: Colors.orange[800],
                    fontSize: 16.0,
                    fontWeight: FontWeight.bold),
              ),
            ],
          ),
          SizedBox(height: 20.0,),
          GestureDetector(
            onTap: () {},
            child: Container(
              height: 40.0,
              decoration: BoxDecoration(
                color: Colors.orange[800],
                borderRadius: BorderRadius.circular(0.0),
              ),
              child: Center(
                child: Text(
                  "Checkout",
                  style: TextStyle(
                    color: Colors.white,
                    fontSize: 12.0,
                    fontWeight: FontWeight.bold,
                  ),
                ),
              ),
            ),
          ),
          SizedBox(
            height: 20.0,
          ),
        ],
      ),
    );
  }
}

class CartListView extends StatefulWidget {
  VoidCallback callback;

  CartListView(this.callback);
  @override
  _CartListViewState createState() => _CartListViewState();
}

class _CartListViewState extends State<CartListView> {
  int _counter = 1;
  int getPrice(int i, int priceC) {
    cartConstant.packageCount = i * priceC;
    return cartConstant.packageCount;
  }

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.only(top:15.0),
      child: Card(
        child: Padding(
          padding: EdgeInsets.symmetric(horizontal: 5.0, vertical: 12.0),
          child: Row(
            mainAxisSize: MainAxisSize.max,
            crossAxisAlignment: CrossAxisAlignment.start,
            children: <Widget>[
              Container(
                decoration: BoxDecoration(
                  border: Border.all(color: Color(0xFFD3D3D3), width: 2.0),
                  borderRadius: BorderRadius.circular(10.0),
                ),
                child: Padding(
                  padding: EdgeInsets.symmetric(
                    horizontal: 5.0,
                  ),
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.center,
                    children: <Widget>[
                      InkWell(
                          onTap: () {
                            setState(() {
                              _counter++;
                              if (_counter > 20) {
                                _counter = 20;
                              }
                            });

                            widget.callback();
                          },
                          child: Icon(Icons.add, color: Color(0xFFD3D3D3))),
                      Text(
                        "$_counter",
                        style: TextStyle(fontSize: 18.0, color: Colors.grey),
                      ),
                      InkWell(
                          onTap: () {
                            setState(() {
                              _counter--;
                              if (_counter < 2) {
                                _counter = 1;
                              }
                            });

                            widget.callback();
                          },
                          child: Icon(Icons.remove, color: Color(0xFFD3D3D3))),
                    ],
                  ),
                ),
              ),
              SizedBox(width: 10.0,),
              Container(
                height: 70.0,
                width: 70.0,
                decoration: BoxDecoration(
                    image: DecorationImage(
                        image: AssetImage("assets/images/img3.jpg"),
                        fit: BoxFit.cover),
                    borderRadius: BorderRadius.circular(35.0),
                    boxShadow: [
                      BoxShadow(
                          color: Colors.black54,
                          blurRadius: 5.0,
                          offset: Offset(0.0, 2.0))
                    ]),
              ),
              SizedBox(width: 15.0,),
              Column(
                mainAxisAlignment: MainAxisAlignment.start,
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                  Text(
                    "Employee Package",
                    style: TextStyle(fontSize: 12.0, fontWeight: FontWeight.bold),
                  ),
                  SizedBox(height: 5.0),
                  SizedBox(height: 5.0),
                  Container(
                    height: 25.0,
                    width: 120.0,
                    child: ListView(
                      scrollDirection: Axis.horizontal,
                      children: <Widget>[
                        Row(
                          children: <Widget>[
                            Text("Price: ",
                                style: TextStyle(
                                    color: Colors.black45,
                                    fontWeight: FontWeight.bold)),
                            SizedBox(width: 5.0,),
                            InkWell(
                              onTap: () {},
                              child: Text(
                                getPrice(_counter, 2000).toString(),
                                style: TextStyle(
                                  fontWeight: FontWeight.bold,
                                  color: Colors.orange[800],
                                ),
                              ),
                            ),
                            SizedBox(
                              width: 10.0,
                            ),
                          ],
                        ),
                      ],
                    ),
                  ),
                ],
              ),
              Spacer(),
              GestureDetector(
                onTap: () {},
                child: Icon(
                  Icons.cancel,
                  color: Colors.grey,
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}