How to change a bottom navigation bar icon in the setState() function in flutter? - flutter

Question

I'm building a food ordering app in flutter. What I want is, when the user adds items to the cart, I want the cart icon in the bottom navigation bar to obtain a red dot on top to notify the user of the addition of items to the cart.
To achieve this, I have created a global variable called no_of_cart_items and when the user adds an item to the cart, I increment this variable in the setState() function as follows:
setState(() {
GlobalVariables.no_of_cart_items+=1;
// change icon here
});
In this setState() function, I wish to change the icon in the bottom navigation bar. How should I do this?
Thank you.
FULL CODE
This is main.dart
//import lines
void main() => runApp(CanteenApp());
class CanteenApp extends StatefulWidget {
#override
_CanteenAppState createState() => _CanteenAppState();
}
class _CanteenAppState extends State<CanteenApp> {
int _currentindex=0; // index of bottom tab
int admin=GlobalVariables.admin;
BottomNavigationBadge badger = new BottomNavigationBadge(
backgroundColor: Colors.red,
badgeShape: BottomNavigationBadgeShape.circle,
textColor: Colors.white,
position: BottomNavigationBadgePosition.topRight,
textSize: 8);
Widget callpage(int currentIndex) {
switch (currentIndex) {
case 0: return UserProfile();
case 1: return Menu();
case 2: return Cart();
break;
default: return UserProfile();
}
}
#override
Widget build(BuildContext context) {
if(admin==1 && _currentindex==2) {
//if you're the admin and have called the history page
return MaterialApp(
debugShowCheckedModeBanner: false,
home: DefaultTabController(
length: 2,
child: Scaffold(
resizeToAvoidBottomPadding: false,
appBar: PreferredSize(
preferredSize: Size.fromHeight(80.0),
child: AppBar(
bottom: TabBar(
indicatorColor: Colors.white,
indicatorWeight: 5,
tabs: <Widget>[
Tab(
child: Align(
alignment: Alignment.center,
child: Text(
'Order History',
style: TextStyle(
fontSize: 20
),
)
)
),
Tab(
child: Align(
alignment: Alignment.center,
child: Text(
'Deposit / Withdraw\nHistory',
style: TextStyle(
fontSize: 17
),
textAlign: TextAlign.center,
)
)
),
],
),
),
),
body: TabBarView(
children: <Widget>[
AdminOrderHistory(),
DepositWithdrawHistory()
],
),
bottomNavigationBar: BottomNavigationBar(
elevation: 10,
currentIndex: _currentindex,
items: [
BottomNavigationBarItem(
icon: Icon(Icons.account_circle),
title: Text('Profile'),
),
BottomNavigationBarItem(
icon: Icon(Icons.restaurant_menu),
title: Text('Menu'),
),
BottomNavigationBarItem(
icon: Icon(Icons.history),
title: Text('History'),
),
],
onTap: (index){
setState(() {
_currentindex=index;
});
}
),
),
),
theme: appTheme,
);
}
else if(admin==1){
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
resizeToAvoidBottomPadding: false,
body: callpage(_currentindex),
bottomNavigationBar: BottomNavigationBar(
elevation: 10,
currentIndex: _currentindex,
items: [
BottomNavigationBarItem(
icon: Icon(Icons.account_circle),
title: Text('Profile'),
),
BottomNavigationBarItem(
icon: Icon(Icons.restaurant_menu),
title: Text('Menu'),
),
BottomNavigationBarItem(
icon: Icon(Icons.history),
title: Text('History'),
),
],
onTap: (index){
setState(() {
_currentindex=index;
});
}
),
),
theme: appTheme,
);
}
else if(admin==0){
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
resizeToAvoidBottomPadding: false,
body: callpage(_currentindex),
bottomNavigationBar:BottomNavigationBar(
elevation: 10,
currentIndex: _currentindex,
items: [
BottomNavigationBarItem(
icon: Icon(Icons.account_circle),
title: Text('Profile'),
),
BottomNavigationBarItem(
icon: Icon(Icons.restaurant_menu),
title: Text('Menu'),
),
BottomNavigationBarItem(
title: Text('Cart'),
icon: Badge(
showBadge: true,
badgeContent: Text(
GlobalVariables.no_of_cart_items.toString(),
style: TextStyle(
color: Colors.white
),
),
child: Icon(Icons.shopping_cart)
)
),
],
onTap: (index){
setState(() {
_currentindex=index;
});
}
),
),
theme: appTheme,
);
}
}
}
This is menu.dart
//import lines
int admin=GlobalVariables.admin;
List snacksmenuitems=[
['Vada Pav', 15],
['Samosa Pav', 15],
['Punjabi Samosa', 25],
['Pav', 5]
];
List ricemenuitems=[
['Fried Rice', 62],
['Schezwan Rice', 69],
['Singapore Rice', 69],
['Manchow Rice', 73],
];
class Menu extends StatefulWidget {
#override
_MenuState createState() => _MenuState();
}
class _MenuState extends State<Menu> {
#override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
MenuTopPart(),
MenuBottomPart(),
],
);
}
}
Color firstColor = Color(0xFFF47D15);
Color secondColor = Color(0xFFEF772C);
class MenuTopPart extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Stack(
children: <Widget>[
ClipPath(
clipper: CustomShapeClipper(),
child: Container(
height:140.0,
width:MediaQuery.of(context).size.width,
decoration: BoxDecoration(
gradient: LinearGradient(
colors: [firstColor, secondColor],
)
),
child: Column(
children: <Widget>[
SizedBox(height: 53.0),
Text(
'MENU',
style: TextStyle(
fontSize: 30.0,
color: Colors.white,
),
textAlign: TextAlign.center,
),
],
)
)
)
],
);
}
}
class MenuBottomPart extends StatefulWidget {
#override
_MenuBottomPartState createState() => _MenuBottomPartState();
}
class _MenuBottomPartState extends State<MenuBottomPart> {
#override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
SizedBox(height: 10),
SizedBox(height: 10),
Padding(
padding: const EdgeInsets.fromLTRB(20, 0, 20, 10),
child: Container(
height: MediaQuery
.of(context)
.size
.height * 0.60,
child: ListView(
padding: EdgeInsets.fromLTRB(0, 0, 0, 0),
scrollDirection: Axis.vertical,
children: <Widget>[
Card(
child: Padding(
padding: const EdgeInsets.fromLTRB(5, 0, 5, 0),
child: ExpansionTile(
title: Text('SNACKS'),
children: snacksmenuitems.map((menuitem) {
//print(menuitem);
return MenuItem(menuitem: menuitem);
/*SizedBox(height:10),
MenuItem(),
SizedBox(height:10),
MenuItem(),
SizedBox(height:10),
MenuItem()*/
}).toList()
),
)
),
SizedBox(height: 10),
Card(
child: Padding(
padding: const EdgeInsets.fromLTRB(5, 0, 5, 0),
child: ExpansionTile(
title: Text('RICE ITEMS'),
children: ricemenuitems.map((menuitem) {
//print(menuitem);
return MenuItem(menuitem: menuitem);
/*SizedBox(height:10),
MenuItem(),
SizedBox(height:10),
MenuItem(),
SizedBox(height:10),
MenuItem()*/
}).toList()
),
)
)
]
),
),
)
]
);
}
}
class MenuItem extends StatefulWidget {
List menuitem=[];
MenuItem({Key key, this.menuitem}): super(key: key);
#override
_MenuItemState createState() => _MenuItemState();
}
class _MenuItemState extends State<MenuItem> {
#override
Widget build(BuildContext context) {
return Container(
margin: const EdgeInsets.only(bottom: 10),
decoration: BoxDecoration(
border: Border.all(color: Colors.black12),
borderRadius: BorderRadius.all(Radius.circular(10))
),
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Image(
image: NetworkImage('https://www.whiskaffair.com/wp-content/uploads/2018/08/Mumbai-Pav-Bhaji-4.jpg'),
width: 80,
height: 80
),
SizedBox(width:10),
Padding(
padding: const EdgeInsets.fromLTRB(0, 5, 0, 0),
child: Container(
width:190,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
widget.menuitem[0],
style: TextStyle(
fontSize:19,
color: Colors.grey[900]
),
),
SizedBox(height:5.0),
Padding(
padding: const EdgeInsets.fromLTRB(0, 10, 0, 0),
child: Row(
children: <Widget>[
Row(
children: <Widget>[
Text(
'₹',
style: TextStyle(
fontSize: 15,
color: Colors.grey[800]
),
),
Text(
widget.menuitem[1].toString(),
style: TextStyle(
fontSize: 15,
color: Colors.grey[800]
),
)
],
),
SizedBox(width:70),
Container(
child: Row(
children: <Widget>[
SizedBox(
width:30,
height:30,
child: FloatingActionButton(
onPressed: (){
setState(() {
if(GlobalVariables.allcartitems[widget.menuitem[0]][0]>0){
GlobalVariables.no_of_cart_items-=1;
GlobalVariables.allcartitems[widget.menuitem[0]][0]-=1;
GlobalVariables.totalcost-=GlobalVariables.allcartitems[widget.menuitem[0]][1];
// CHECK IF CART HAS NO ITEMS AND REMOVE BADGE HERE
}
});
},
elevation: 1,
child: Icon(Icons.remove, size: 18),
backgroundColor: Colors.red[300],
mini: true,
shape: RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(5.0))),
),
),
Padding(
padding: const EdgeInsets.fromLTRB(5, 0, 5, 0),
child: Text(
GlobalVariables.allcartitems[widget.menuitem[0]][0].toString(),
style: TextStyle(
fontSize: 18
),
),
),
SizedBox(
width:30,
height:30,
child: FloatingActionButton(
onPressed: (){
setState(() {
GlobalVariables.no_of_cart_items+=1;
GlobalVariables.allcartitems[widget.menuitem[0]][0]+=1;
GlobalVariables.totalcost+=GlobalVariables.allcartitems[widget.menuitem[0]][1];
// SET BADGE HERE
});
},
elevation: 1,
child: Icon(Icons.add, size: 20),
backgroundColor: Colors.green[300],
mini:true,
shape: RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(5.0))),
),
)
],
)
)
],
),
),
],
),
),
)
],
),
);
}
}
This is cart.dart:
import 'dart:convert';
import 'package:canteen_app/pages/globalvar.dart';
import 'package:canteen_app/pages/globalvar.dart' as prefix0;
import 'package:canteen_app/pages/orderReceipt.dart';
import 'package:flutter/material.dart';
import 'package:canteen_app/pages/CustomShapeClipper.dart';
import 'package:http/http.dart' as http;
import 'package:intl/intl.dart';
class Cart extends StatefulWidget {
#override
_CartState createState() => _CartState();
}
class _CartState extends State<Cart> {
#override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
CartTopPart(),
CartBottomPart()
],
);
}
}
class CartTopPart extends StatefulWidget {
#override
_CartTopPartState createState() => _CartTopPartState();
}
Color firstColor = Color(0xFFF47D15);
Color secondColor = Color(0xFFEF772C);
class _CartTopPartState extends State<CartTopPart> {
#override
Widget build(BuildContext context) {
return Stack(
children: <Widget>[
ClipPath(
clipper: CustomShapeClipper(),
child: Container(
height:140.0,
width:MediaQuery.of(context).size.width,
decoration: BoxDecoration(
gradient: LinearGradient(
colors: [firstColor, secondColor],
)
),
child: Column(
children: <Widget>[
SizedBox(height: 53.0),
Text(
'CART',
style: TextStyle(
fontSize: 30.0,
color: Colors.white,
),
textAlign: TextAlign.center,
),
],
)
)
)
],
);
}
}
var cartmenuitems = GlobalVariables.allcartitems.keys.toList();
class CartBottomPart extends StatefulWidget {
#override
_CartBottomPartState createState() => _CartBottomPartState();
}
class _CartBottomPartState extends State<CartBottomPart> {
bool _isLoading=false;
createAlertDialog(BuildContext context, String errormessage){
return showDialog(
context: context,
builder: (context){
return AlertDialog(
content: Text(errormessage)
);
}
);
}
#override
Widget build(BuildContext context) {
if(GlobalVariables.no_of_cart_items>0) {
return _isLoading==true ? Center(child: CircularProgressIndicator()) : Padding(
padding: const EdgeInsets.fromLTRB(20, 10, 20, 10),
child: Column(
children: <Widget>[
Container(
height: MediaQuery
.of(context)
.size
.height * 0.40,
child: ListView(
padding: EdgeInsets.fromLTRB(0, 10, 0, 0),
scrollDirection: Axis.vertical,
children: cartmenuitems.map((menuitem) {
//print(cartmenuitems);
// print(GlobalVariables.allcartitems[menuitem]);
//if(GlobalVariables.allcartitems[menuitem]>=1) {
//print('heyy');
return CartOrderDish(menuitem: menuitem);
//}
}).toList()
),
),
Divider(
color: Colors.black
),
Row(
children: <Widget>[
Text(
'Total Amount:',
style: TextStyle(
fontSize: 20
),
),
SizedBox(width: 140),
Row(
children: <Widget>[
Text(
'₹',
style: TextStyle(
fontSize: 20
),
),
Text(
GlobalVariables.totalcost.toString(),
style: TextStyle(
fontSize: 20
)
)
],
)
],
),
SizedBox(height: 5),
Align(
alignment: Alignment.centerLeft,
child: Text(
'(Inclusive of GST)',
style: TextStyle(
fontSize: 15
),
),
),
SizedBox(height: 18),
RaisedButton(
onPressed: () {
if((GlobalVariables.accountbalance-GlobalVariables.totalcost)<0){
createAlertDialog(context, "Whoops! The total cost exceeds your account balance!\n\nYour account balance can be updated at the CASH COUNTER.");
}
else {
setState(() {
_isLoading = true;
});
// creating a list of all cart items to send to php
List cart = [];
cartmenuitems.map((menuitem) {
if (GlobalVariables.allcartitems[menuitem][0] > 0) {
cart.add([menuitem, GlobalVariables.allcartitems[menuitem][0], GlobalVariables.allcartitems[menuitem][1] * GlobalVariables.allcartitems[menuitem][0]]);
}
}).toList();
print(jsonEncode(cart));
Future placeOrderFunction() async {
print(GlobalVariables.username);
final response = await http.post(
"https://kjscecanteenapp.000webhostapp.com/place_order_sys.php",
body: {
"cart": json.encode(cart),
"username": GlobalVariables.username
});
// print(response.body);
var decodedResponse = json.decode(response.body);
print(decodedResponse);
setState(() {
_isLoading = false;
});
if (decodedResponse['error'] != -1) {
// means no error
int orderId=decodedResponse['error'];
int cost=GlobalVariables.totalcost;
GlobalVariables.no_of_cart_items = 0;
String date=DateFormat('dd-MMM-yyyy').format(DateTime.now());
cartmenuitems.map((menuitem) {
if (GlobalVariables.allcartitems[menuitem][0] > 0) {
GlobalVariables.allcartitems[menuitem][0] = 0;
}
});
GlobalVariables ob = new GlobalVariables();
ob.resetcart();
GlobalVariables.accountbalance -= GlobalVariables.totalcost;
GlobalVariables.totalcost = 0;
Navigator.of(context)
.push(MaterialPageRoute<Null>(
builder: (BuildContext context) {
return new OrderReceipt(orderId: orderId, cost: cost, date: date, cart: cart);
}));
}
else{
createAlertDialog(context, "There was some error during the order placement. Don't worry tho try again in a few seconds!");
}
}
placeOrderFunction();
}
},
elevation: 5.0,
textColor: Colors.white,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(5.0)),
padding: const EdgeInsets.all(0.0),
child: Container(
decoration: const BoxDecoration(
gradient: LinearGradient(
colors: <Color>[
Color(0xFF0083B0),
Color(0xFF00B4DB),
]
)
),
padding: const EdgeInsets.fromLTRB(40, 15, 40, 15),
child: Text(
'Place Order',
style: TextStyle(
fontSize: 20
),
),
)
)
],
),
);
}
else {
return Padding(
padding: const EdgeInsets.all(20.0),
child: Container(
height: MediaQuery.of(context).size.height*0.6,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Text(
'Please add some items into your cart.',
style: TextStyle(
fontSize: 20,
),
textAlign: TextAlign.center,
),
],
),
),
);
}
}
}
class CartOrderDish extends StatefulWidget {
String menuitem;
CartOrderDish({Key key, this.menuitem}): super(key: key);
#override
_CartOrderDishState createState() => _CartOrderDishState();
}
class _CartOrderDishState extends State<CartOrderDish> {
#override
Widget build(BuildContext context) {
if(GlobalVariables.allcartitems[widget.menuitem][0]>0) {
int price=GlobalVariables.allcartitems[widget.menuitem][0]*GlobalVariables.allcartitems[widget.menuitem][1];
return Padding(
padding: const EdgeInsets.fromLTRB(0, 0, 0, 10),
child: Row(
children: <Widget>[
Expanded(
child: Text(
widget.menuitem,
style: TextStyle(
fontSize: 20
),
),
),
SizedBox(width: 50),
Container(
child: Row(
children: <Widget>[
SizedBox(
width: 30,
height: 30,
child: FloatingActionButton(
heroTag: 'fab1',
elevation: 1,
child: Icon(Icons.remove, size: 18),
backgroundColor: Colors.red[300],
mini: true,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(5.0))),
),
),
Padding(
padding: const EdgeInsets.fromLTRB(5, 0, 5, 0),
child: Text(
GlobalVariables.allcartitems[widget.menuitem][0].toString(),
style: TextStyle(
fontSize: 18
),
),
),
SizedBox(
width: 30,
height: 30,
child: FloatingActionButton(
heroTag: 'fab2',
elevation: 1,
child: Icon(Icons.add, size: 20),
backgroundColor: Colors.green[300],
mini: true,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(5.0))),
),
)
],
)
),
SizedBox(width: 50),
Row(
children: <Widget>[
Text(
'₹',
style: TextStyle(
fontSize: 20
),
),
Text(
price.toString(),
style: TextStyle(
fontSize:20
)
)
],
)
],
),
);
}
else{
return Container();
}
}
}

Answer 1

Instead of changing the entire icon to indicate items added to cart, you could use Badge
Badge package: https://pub.dev/packages/badges
Update-1: For implementing the badges:
var p1badge = false;
var p2badge = false;
List<BottomNavigationBarItem> buildBottomNavBarItems() {
return [
BottomNavigationBarItem(
icon: Badge(
showBadge: p1badge,
child: Icon(Icons.filter_1),
),
title: Text('Page-1')),
BottomNavigationBarItem(
icon: Badge(
showBadge: p2badge,
child: Icon(Icons.filter_2),
),
title: Text('Page-2'))
];
}
Use a VoidCallback to update the badge:
class Page1 extends StatelessWidget {
VoidCallback onP1Badge;
Page1({this.onP1Badge});
#override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
RaisedButton(
child: Text('P1 BADGE'),
onPressed: () {onP1Badge();},
),
],
);
}
}
Change the value of p1badge to true and call setState():
pages = [
Page1(
onP1Badge: () {
p1badge = true;
setState(() {});
},
),
Page2()
];
Update-2: Check this out: https://github.com/TheArhaam/Flutter-BottomNavigationBar-Badge
GIF: