Count number of documents with a particular field in a collection Firestore Flutter

Question

I have made an app in flutter that saves my user's data in Firestore with Flutter. I have made a collection called "Result" which has multiple documents, each with a document having the result of "Normal" or "COVID". What I want to do is get a count of all people with the result = COVID and display it in my flutter application.

CollectionReference reference= (await FirebaseFirestore.instance.collection('Result').add({
  "date" :Timestamp.now().millisecondsSinceEpoch.toString(),
  "result": _results[0]["label"],
})) as CollectionReference<Object?>;

In short, I expect something like this:

Below code prints, Records are 3

void Result() async{
  var query = FirebaseFirestore.instance.collection("Result");
  var snapshot = await query.get();
  var count = snapshot.size;
  print(' Records are $count');   //Records are 3
}

I want Result function to display this count when I press Generate Report. Hope so now I'm a bit clear.

    enter code hereimport 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

class GenerateReport extends StatefulWidget {
  const GenerateReport({Key? key}) : super(key: key);

  @override
  State<GenerateReport> createState() => _GenerateReportState();
}

class _GenerateReportState extends State<GenerateReport> {

  //final fireStore= FirebaseFirestore.instance.collection('Result').where('result' , isEqualTo: 'COVID').count('result').snapshots();
  final fireStore= FirebaseFirestore.instance.collection('Result').snapshots();

  Result() async{
    var query = await FirebaseFirestore.instance.collection("Result").where('result' , isEqualTo: 'COVID');
    var snapshot = await query.get();
    var count = snapshot.size; //return count;
    print ('RESULTS ARE  $count');
  }
  /* print(' Records are $count');  return Text ('Normal  : $count',);//Records are 3 Future<Text> Result() async{*/


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        centerTitle: true,
        title: const Text('Generate Report'),
        flexibleSpace: Container(
          decoration: const BoxDecoration(
            gradient: LinearGradient(
                begin: FractionalOffset.topCenter,
                end: FractionalOffset.bottomCenter,
                colors: <Color>[
                  Color.fromRGBO(47, 75, 104, 0.7),
                  Color.fromRGBO(47, 75, 104, 1)
                ]),
          ),
        ),
        backgroundColor: Colors.transparent,
      ),
      //centerTitle: true,
      // backgroundColor: const Color.fromRGBO(47, 75, 104,1),
      body: Center(
        child: Column(
          children: <Widget>[
            const SizedBox(
              height: 200,
            ),
            ElevatedButton(
              onPressed: Result,
              child: const Text('Generate Report'),
              /*async {
                  FirebaseFirestore.instance.collection('Result').get().then((QuerySnapshot querySnapshot) {
                    querySnapshot.docs.forEach((doc) {
                      print(doc["result"]);
                    });
                  });
                }*/
            ),
            //Result();
            StreamBuilder<QuerySnapshot>(
                stream: fireStore,
                builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
                  if (snapshot.connectionState == ConnectionState.waiting) {
                    return const CircularProgressIndicator();
                  }
                  if (snapshot.hasError) {
                    return const Text('Some error ');
                  }
                  return Expanded(
                    child: ListView.builder(
                        itemCount: snapshot.data!.docs.length,
                        itemBuilder: (context, index) {
                          return ListTile(
                            title: Text(snapshot.data!.docs[index]['result'].toString()),     //shows list of results
                          );
                        }),
                  );
                }
            ),
          ],
        ),
      ),
    );
  }

}

Here I can see list of results not the exact count app

Answer 1

you need to aply a filter query with where over that collection, use this:

 void Result() async{
  var query = FirebaseFirestore.instance.collection("Result").where("result", isEqualTo: "COVID");
  var snapshot = await query.get();
  var count = snapshot.size;
  print(' Records are $count');  
}

now it should get and print the count of the documents with a "COVID" value in the result field.