我正在快速开发一个食品订购应用程序。我想要的是,当用户将商品添加到购物车时,我希望底部导航栏中的购物车图标在顶部获得一个红点,以通知用户商品已添加到购物车。
[为了实现这一点,我创建了一个名为no_of_cart_items
的全局变量,当用户将商品添加到购物车时,我按如下所示在setState()
函数中递增此变量:
setState(() {
GlobalVariables.no_of_cart_items+=1;
// change icon here
});
在此setState()
功能中,我希望更改底部导航栏中的图标。我应该怎么做?谢谢。
编辑
这是我在main.dart
中的代码
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(
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,
);
这是我的menu.dart
文件。在这里,有两个按钮:每个菜盘的plus
和minus
可以从购物车中添加或减去它,在这些按钮的onTap()
功能中,我想在底部设置购物车图标的徽章导航
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];
}
});
},
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 for cart icon
});
},
elevation: 1,
child: Icon(Icons.add, size: 20),
backgroundColor: Colors.green[300],
mini:true,
shape: RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(5.0))),
),
)
],
)
)
],
),
),
],
),
),
)
],
),
);
您可以使用Badge
而不是更改整个图标来表示已添加到购物车的项目Badge
套件:https://pub.dev/packages/badges更新:用于实施徽章:
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'))
];
}
使用VoidCallback更新徽章:
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();},
),
],
);
}
}
将p1badge
的值更改为true
并调用setState()
:
pages = [
Page1(
onP1Badge: () {
p1badge = true;
setState(() {});
},
),
Page2()
];