Loading only specific data from Firestore using StreamBuilder in Flutter/Dart - asynchronous

Question

I am trying to load data from Firestore using StreamBuilder.
In my collection called 'connect' there are may documents.
But I want to load only specific documents.
'connections' is a List that contains some keys in 'connect' collection.
'hello' is a QuerySnapshot List that contains some documents in 'collection' collection.
For example, if my DB contains documents with documentID of followings:
-LK5SAToCPhI1Zp5W_bL
-LK5Ypv0HeDCwcN4K41M
-LK5j-OGtNjMpgklUB4B
-LK5mOih9wuz5ZSebXMn
a list 'connections' contains only a portion such as:
-LK5SAToCPhI1Zp5W_bL
-LK5Ypv0HeDCwcN4K41M
In a StreamBuilder I want to load only documents that have same name in connections. How can I load only specific documents?
Please Help me!
Firestore.instance.collection('connect')
.snapshots()
.listen((docSnap) {
for (DocumentSnapshot docs in docSnap.documents) {
if (connections.isNotEmpty) {
for (String keys in connections) {
if (docs.documentID.toString() == keys) {
hello.add(docs);
}
}
}
}
});
#override
Widget build(BuildContext context) {
return new Scaffold(
body: Center(
child: Column(
children: <Widget>[
Row(
children: <Widget>[
Padding(
padding: EdgeInsets.only(bottom: 60.0),
),
Expanded(
child: Text(
"Invitation!",
style: TextStyle(fontWeight: FontWeight.bold),
textAlign: TextAlign.center,
),
),
],
),
Flexible(
child: StreamBuilder<QuerySnapshot>(
stream: Firestore.instance.collection('connect').snapshots(),
builder:
(BuildContext context,
AsyncSnapshot<QuerySnapshot> snapshot) {
if (!snapshot.hasData) return const Text("Loading ... ");
final int messageCount = snapshot.data.documents.length;
return ListView.builder(
padding: const EdgeInsets.symmetric(horizontal: 8.0),
itemCount: messageCount,
itemBuilder: (_, int index) {
final DocumentSnapshot document =
snapshot.data.documents[index];
if (document.documentID ==
hello[index].documentID) {
return Container(
child: Row(
children: <Widget>[
Text("Hello $messageCount")
],
),
);
} else {
return Container(
child: Row(
children: <Widget>[Text("Wrong")],
),
);
}
});
},
),
),
_buildLayout(),
],
)));
}