snapshot.data becomes null after half a second - firebase

Question

I have a collection called pending_appointments and I want to access all of the documents which have the field patienduid equal to the current user's uid. Then there is a stream builder, but snapshots.data becomes null.
Like when I go to that screen, it shows me the expected results for about half a second and then it changes to 'No appointment found'.
Also, if I remove that 'where' statement, it shows me all the pending appointments which is the expect result, but as soon as I add the where statement which should give me the desired result, it goes back to no appointment after showing me the desired results for half a second.
Widget build(BuildContext context) {
return SafeArea(
child: StreamBuilder(
stream: FirebaseFirestore.instance
.collection('pending_appointments')
.where('patientUid', isEqualTo: user.uid)
.orderBy('date')
.snapshots(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.connectionState == ConnectionState.active) {
if (snapshot.data != null) {
return ListView.builder(
scrollDirection: Axis.vertical,
physics: ClampingScrollPhysics(),
shrinkWrap: true,
itemCount: snapshot.data.size,
itemBuilder: (context, index) {
DocumentSnapshot document = snapshot.data.docs[index];
print(_compareDate(document['date'].toDate().toString()));
if (_checkDiff(document['date'].toDate())) {
deleteAppointment(document.id);
}
return Card(
elevation: 2,
child: InkWell(
onTap: () {},
child: ExpansionTile(
title: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Padding(
padding: const EdgeInsets.only(left: 5),
child: Text(
'Dr. ${document['doctor']}',
style: GoogleFonts.lato(
fontSize: 16,
fontWeight: FontWeight.bold,
),
),
),
Text(
_compareDate(document['date'].toDate().toString())
? "TODAY"
: "",
style: GoogleFonts.lato(
color: Colors.green,
fontSize: 18,
fontWeight: FontWeight.bold),
),
SizedBox(
width: 0,
),
],
),
subtitle: Padding(
padding: const EdgeInsets.only(left: 5),
child: Text(
_dateFormatter(
document['date'].toDate().toString()),
style: GoogleFonts.lato(),
),
),
children: [
Padding(
padding: const EdgeInsets.only(
bottom: 20, right: 10, left: 16),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text(
"Patient name: " + document['name'],
style: GoogleFonts.lato(
fontSize: 16,
),
),
SizedBox(
height: 10,
),
Text(
"Time: " +
_timeFormatter(
document['date']
.toDate()
.toString(),
),
style: GoogleFonts.lato(
fontSize: 16,
),
),
],
),
IconButton(
tooltip: 'Delete Appointment',
icon: Icon(
Icons.delete,
color: Colors.black87,
),
onPressed: () {
print(">>>>>>>>>" + document.id);
_documentID = document.id;
showAlertDialog(context);
},
),
],
),
),
],
),
),
);
},
);
} else {
return Center(
child: Text(
'No Appointment Scheduled',
style: GoogleFonts.lato(
color: Colors.grey,
fontSize: 18,
),
),
);
}
} else {
return Center(
child: CircularProgressIndicator(),
);
}
},
),
);
}

Answer 1

remove this
if (snapshot.connectionState == ConnectionState.active) {
}
add this to your code
if (Snapshot.connectionState == ConnectionState.waiting) {
return Center(child: CircularProgressIndicator());
}
if (Snapshot.connectionState == ConnectionState.none) {
return Container();
}
if (Snapshot.data.docs.isEmpty) {
return Text(
'Document Empty',
style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),
);
}
if (!Snapshot.hasData) {
return Text(
'0',
style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),
);
}
return ListView.builder(
scrollDirection: Axis.vertical,
physics: ClampingScrollPhysics(),
shrinkWrap: true,
itemCount: snapshot.data.docs.length,
itemBuilder: (context, index) {
final document = snapshot.data.docs[index].data();
print(_compareDate(document['date'].toDate().toString()));
if (_checkDiff(document['date'].toDate())) {
deleteAppointment(document.id);
}
});