Flutter How to apply search filter in a querysnapshot used in Listview builder - flutter

Question

This is my firebase data request code
and this is my future builder based on the qn.docs
How to search within the snapshot and ListView.builder to use the filtered set.
previously I was using a Local List and used to search as on Itemchanged
thanks in advance for your guidance.
I am new to flutter. so please explain with an example
Future <QuerySnapshot> getSpeakernames() async {
QuerySnapshot qn = await
FirebaseFirestore.instance.collection('speakernames').orderBy('speakername').get();
return qn;
}
Center(
child: Container(
child: ListView.builder(
itemCount: snapshot.data.docs.length,
itemBuilder: (BuildContext context, int index) {
DocumentSnapshot data = snapshot.data.docs[index];
return ListTile(title: Text(data.get("speakername")),
subtitle: Text(data.get("speakerdegree")), )
onItemChanged(String value) {
setState(() {
data.get("speakername").
newspeakernames = speakernames
.where((string) =>
string.toLowerCase().contains(value.toLowerCase()))
.toList();
});
}

Answer 1

you can use ".Where" property of Firestore
like below
Future <QuerySnapshot> getSpeakernames() async {
QuerySnapshot qn = await FirebaseFirestore.instance.collection('speakernames')
.where('speakername' , isEqualTo : SubramanianV).orderBy('speakername').get();
return qn;
}

Answer 2

You can use isGreaterThanOrEqualTo.
Example:
class doctorName {
getDoctorByName(String doctorName, String last) async {
return await Firestore.instance
.collection("Doctor")
.where("name", isGreaterThanOrEqualTo: doctorName)
.where("name", isLessThan: last)
//.where("name", isEqualTo: doctorName)
.getDocuments();
}
}