Cant get StreamBuilder to display data from cloud firestore - firebase

Question

I know I have a connection to the database and no errors are appearing so I'm pretty confused. The title and code should summarize the problem fairly well. Think I'm missing something?
here is the main code that should be displaying cards with titles from firebase
mainList() {
StreamBuilder(
stream: Firestore.instance.collection('Events').snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return Text('Loading');
} else {
return ListView.builder(
itemCount: snapshot.data.documents.length,
itemBuilder: (context, index) {
DocumentSnapshot userPost = snapshot.data.documents[index];
return Container(
width: MediaQuery.of(context).size.width,
height: 350.0,
child: Padding(
padding: EdgeInsets.only(top: 8.0, bottom: 8.0),
child: Material(
elevation: 14.0,
shadowColor: Color(0x802196F3),
child: Center(
child: Padding(
padding: EdgeInsets.all(8.0),
child: Column(
children: <Widget>[
Container(
width: MediaQuery.of(context).size.width,
height: 200.0,
child: Text(
'${userPost['title']}',
))
],
),
),
))),
);
},
);
}
});
}
and here is where the function is called:
lass MyAppmain extends State<MyApp> {
#override
Widget build(BuildContext context) {
var listView = ListView.builder(
itemCount: local.length,
itemBuilder: (BuildContext cnxt, int index) {
return new Text(local[index]);
});
return MaterialApp(
home: PageView(
controller: controller,
children: <Widget>[
//home page---------------------------
Scaffold(
appBar: AppBar(
title: Text(
'Events',
),
elevation: 20,
),
//main list view for the cards
//think I use streambuilder for this so google before starting
body: mainList(),//RIGHT HERE
floatingActionButton: FloatingActionButton(
child: Icon(Icons.add),
onPressed: () {
Navigator.push(context, NewEventTransition());
},
mini: true,
),
),
//Profile Page-------------------------------
Scaffold(
appBar: AppBar(
title: Text(
'Profile',
),
elevation: 20,
),
),
],
));
}
}
Want a listview of cards holding the titles from firebase (will soon be more than titles but want to get this working first)

Answer 1

This is a common problem.
return ListView.builder(
itemCount: snapshot.data.documents.length, // this line is the culprit!
itemBuilder: (context, index) {
print(snapshot.data.documents.length); // it will print null
.......
}
See, It takes some time to fetch data from firebase. When ListView.builder is called the value of snapshot.data.documents.length is actually null. Tho after few seconds it gets data but till then ListView had built the UI and that's why it's blank. To check the value, you can add a Print statement like shown above.
Now there are few ways to solve this problem:
Make an int variable say totalLength, make a function say setTotalLength which makes a call to Firebase/Firestore database and use setState to assign this value to totalLength and then change that code to this:
itemCount: totalLength,
You should Call setTotalLength in your initState method.
Or, you can change your code to this, But I'm NOT 100% sure that this will work:
itemCount: snapshot.data.documents.length ?? 0 // returns 0 if the value is null, may reload UI again when data comes