问题
How can i show the total amount in the bottom navigation bar... The app uses firebase backend... I have a filed in my database name total price of each item... Now I want to fetch the total price of each item and then add it and display in the bottom navigation bar..
I have attach my firebase backend screen shot.. what i need is to get all the value of the field 'total' add it up and show it in the bottom bar below the Total which is hardcoded as 999 currently section... It would be helpful if some let me know how to do it.. I am new to app development and flutter as well
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/foundation.dart';
import 'dart:async';
import 'package:fluttertoast/fluttertoast.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
final myController = TextEditingController(); ///Alert Dialog box input text myController will be use to store the number of qty
String id;
var qty;
var price;
var total;
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home:Scaffold(
bottomNavigationBar: new Container( //// Bottom Naviagtion Bar for check out and Total price
color: Colors.white,
child: Row(
children: <Widget>[
Expanded(child: ListTile(
title: Text("Total"),
subtitle: Text("Rs 999"),
),),
Expanded(
child: MaterialButton(onPressed:() {},
child: Text("Check Out",style: TextStyle(color: Colors.white),),
color: Colors.red,) ,
)
],
),
),
appBar: AppBar(title: Text('MyKart'),
),
body: (
StreamBuilder(
stream: Firestore.instance.collection('KartDetails').snapshots(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasData) {
return ListView.builder(
itemCount: snapshot.data.documents.length,
itemBuilder: (context, index) {
DocumentSnapshot kartDetails = snapshot.data.documents[index];
return Container(
height: 150,
child: Card(
elevation: 10,
child: Container(
height: 100,
width: 100,
child: Row(
children: <Widget>[
Container(
width: 100,
height: 100,
child: Image.network(kartDetails['img']),
),
Container(
child: (Text(kartDetails['item'])),
),
Container(
width: 50,
child: (Text('Rs '+kartDetails['price'].toString(),textAlign: TextAlign.end,)),
),
Container(
margin: EdgeInsets.only(left: 20),
height: 120,
width: 50,
color: Colors.white10,
child: Column(
children: <Widget>[
RaisedButton(
color: Colors.grey,
onPressed: (){
showDialog(context: context,
builder: (BuildContext context){
return Dialog(
child: Container(
height: 250,
color: Colors.white10,
child: Container(
margin: EdgeInsets.all(40.0),
child: Column(
children: <Widget>[
TextField(
controller: myController,
keyboardType: TextInputType.number,
decoration: InputDecoration(hintText: 'Enter the Quantity'),
),
Container(
height: 50,
),
RaisedButton(
color: Colors.blue,
child: Text('Submit'),
onPressed: () async{
qty = myController.text;
//==================================================================Total Number of QTY ENTERED==========================================//
if (int.parse(qty)>0 && int.parse(qty)>=5) {
CollectionReference collectionRefernce = Firestore
.instance.collection(
'KartDetails');
QuerySnapshot querySnapshot = await collectionRefernce
.getDocuments();
querySnapshot
.documents[index]
.reference
.updateData(
{"quantity": qty});
//==================================================================Calculate price for each product==========================================//
price = kartDetails['price'];
total=int.parse(qty)*price;
querySnapshot
.documents[index]
.reference
.updateData(
{"total": total});
print(myController
.toString());
Navigator.of(context)
.pop();
myController.clear();
Fluttertoast.showToast(msg: "Quantity Updated",
toastLength: Toast.LENGTH_LONG,
gravity: ToastGravity.CENTER,
timeInSecForIosWeb: 1,
backgroundColor: Colors.red,
textColor: Colors.white,
fontSize: 20.0
);
}
else if(int.parse(qty) < 5 || int.parse(qty)<0) {
Fluttertoast.showToast(msg: "Minimum 5 quanity",
toastLength: Toast.LENGTH_LONG,
gravity: ToastGravity.CENTER,
timeInSecForIosWeb: 1,
backgroundColor: Colors.red,
textColor: Colors.white,
fontSize: 20.0
);
myController.clear();
}
else {
Fluttertoast.showToast(msg: "Please enter valid quantity",
toastLength: Toast.LENGTH_LONG,
gravity: ToastGravity.CENTER,
timeInSecForIosWeb: 1,
backgroundColor: Colors.red,
textColor: Colors.white,
fontSize: 20.0
);
myController.clear();
}
//Firebase query
},
)
],
),
),
),
);
});
},
child: Icon(Icons.shopping_basket),
),
Container(
height: 20,
),
RaisedButton(
color: Colors.grey,
child: Icon(Icons.delete,color: Colors.black87,),
)
],
),
),
Column(
children: <Widget>[
Container(
margin: EdgeInsets.only(left: 3),
height: 50,
width: 70,
child: Center(child: Text('Quantity')),
),
Container(
width: 70,
child: Center(child: Text((kartDetails['quantity']).toString())),
),
Container(
margin: EdgeInsets.only(top: 25),
child: Center(child: Text('Total Price')),),
Container(
margin: EdgeInsets.only(left: 3),
width: 70,
child: Center(child: Text(("Rs " + (kartDetails['total']).toString()))),
),
],
),
],
),
),
),
);
},
);
}
else{
return Center(
child: Container(),
);;
}
},
)
),
),
);
}
}
回答1:
You can easily do it with this method:
var totalCartValue = 0;
String getCartTotal() async {
QuerySnapshot snapshot = await Firestore.instance
.collection('KartDetails')
.getDocuments();
snapshot.documents.forEach((doc) {
setState((){
totalCartValue += doc.data['total'];
});
});
return totalCartValue.toString();
}
P.S: This method will give you the total of all values in the KartDetails collection not the total for the current user, for the current user it should be like this:
var totalCartValue = 0;
String getCartTotal() async {
QuerySnapshot snapshot = await Firestore.instance
.collection('KartDetails')
.where("UID", isEqualTo: FirebaseAuth.instance.currentUser().toString())
.getDocuments();
snapshot.documents.forEach((doc) {
setState((){
totalCartValue += doc.data['total'];
});
});
return totalCartValue.toString();
}
And use it in the UI that way:
class YourClassName extends StatefulWidget {
@override
_YourClassNameState createState() => _YourClassNameState();
}
class _YourClassNameState extends State<YourClassName> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: //your body code,
bottomNavigationBar: BottomNavigationBar(
items: [
BottomNavigationBarItem(
icon: new Icon(Icons.cart_shopping),
title: new Text(totalCartValue),
),
]
)
);
}
}
You should call it inside your initState so it gets executed whenever app starts:
@override
initState(){
super.initState();
getCartTotal();
}
回答2:
This is a very vague question, so I will give a shot at one method of solving this. In order to do this you will need some sort of state management solution. I suggest using provider. Flutter has a tutorial on provider here. Essentially you will have to create a ChangeNotifier that every time would onAddItem and onDeleteItem and call notifyListeners() whenever you add or delete items. Then your bottom bar would simply use a Consumer to get the values from your ChangeNotifier. As I said this is just one approach, but since you did not give a replicable example this is the best I can do.
来源：https://stackoverflow.com/questions/63115524/want-to-pass-the-total-price-in-the-bottom-navigation-bar-in-flutter