StreamBuilder ListView returns empty list from Firestore on first load

It is not fetched by using any one of those query snapshot and document snapshot

You should query at first using Querysnapshot and then retrieve the information to a Documentsnapshot Yes, it may take a few seconds to load the document the solution is correct that you should async and await function

Instead of streamBuilder, I suggest you use Direct snapshot

we can load the document snapshot in the initstate of a statefullWidget works when your class is a statefullWidget and the problem is also related to the state

...

 bool isLoading;
 List<DocumentSnapshot> activity =[];
 QuerySnapshot user;
 @override
 void initState() {
  print("in init state");
  super.initState();
  getDocument();
 ``    } 
  getDocument() async{

 setState(() {
   isLoading = true;
 });
 user= await Firestore.instance
    .collection("users")
    .document(widget.userId)
    .collection('activities')
    .orderBy('startDate', descending: true)     
    .getDocuments();

  activity.isEmpty ? activity.addAll(user.documents) : null;

    setState(() {
  isLoading = false;
       });

     }

//inside  Widget build(BuildContext context) { return  Scaffold( in your body 
//section of scaffold in the cointainer
Container(
padding: const EdgeInsets.all(20.0),
child: isLoading ?
         CircularProgressIndicator(),
        :ListView.builder(

                          itemCount: global.category.length,
                          itemBuilder: (context, index) {
                            return  PointCard(
                                    title: activity[index].data['title'],
                                      type: activity[index].data['type'],
                                    );//pointcard
                             }
                            ),//builder
                     ),//container

We can also give a try for the following

 QuerySnapshot qs;
 Stream<QuerySnapshot> provideActivityStream() async{
    qs= await Firestore.instance
             .collection("users")
             .document(widget.userId)
             .collection('activities')
            .orderBy('startDate', descending: true)     
            .snapshots();

      return qs;
  }//this should work

but as per the basics of streambuilder if the above piece didn't work then there is another

     QuerySnapshot qs;
 Stream<QuerySnapshot> provideActivityStream() async* {
    qs= await Firestore.instance
             .collection("users")
             .document(widget.userId)
             .collection('activities')
            .orderBy('startDate', descending: true)     
            .snapshots();

      yield qs;
  }//give this a try

tl;dr

• Needed to use setState to get the Firebase currentUser uid to be available for the widgets
• Needed to use AutomaticKeepAliveClientMixin to work correctly with TabBar
• I think using the Provider package may be a better way of persisting the user's state but didn't in solving this problem

Explanation

My code gets the currentUser uid with a Future. As per the the SO answer here that's a problem because the widgets will all be built before FirebaseAuth can give back the uid. I initially tried to use initState to get the uid but that has exactly the same synchronous problem. Calling setState from the function to call the FirebaseAuth.instance allowed the widget tree to update.

I'm placing this widget within a TabBar widget. My understanding is that everytime a tab is removed from view it's disposed of so rebuilt when returned. This was causing further state issues. API docs for the AutomaticKeepAlive mixin are here

Solution code

With added comments in the hope they're helpful for someone else's understanding (or someone can correct my misunderstanding)

activitylist.dart

class ActivityList extends StatefulWidget {
// Need a stateful widget to use initState and setState later
  @override
  _ActivityListState createState() => _ActivityListState();
}

class _ActivityListState extends State<ActivityList> 
  with AutomaticKeepAliveClientMixin<ActivityList>{
  // `with AutomaticKeepAliveClientMixin` added for TabBar state issues

  @override
  bool get wantKeepAlive => true;
  // above override required for mixin

  final databaseReference = Firestore.instance;

  @override
    initState() {
      this.getCurrentUser(); // call the void getCurrentUser function
      super.initState();
  }

  FirebaseUser currentUser;

  void getCurrentUser() async {
    currentUser = await FirebaseAuth.instance.currentUser();
    setState(() {
      currentUser.uid;
    });
    // calling setState allows widgets to access uid and access stream
  }

  Stream<QuerySnapshot> provideActivityStream() async* {
    yield* Firestore.instance
        .collection("users")
        .document(currentUser.uid)
        .collection('activities')
        .orderBy('startDate', descending: true)     
        .snapshots();
  }

  @override
  Widget build(BuildContext context) {
    super.build(context);
    return Container(
                  padding: const EdgeInsets.all(20.0),
                  child: StreamBuilder<QuerySnapshot>(
                  stream: provideActivityStream(),
                  builder: (BuildContext context,
                  AsyncSnapshot<QuerySnapshot> snapshot) {
                    if(snapshot.hasError) return CircularProgressIndicator();
                    if(snapshot.data == null) return CircularProgressIndicator();
                    else if(snapshot.data !=null) {
                      return new ListView(
                          children: snapshot.data.documents.map((
                              DocumentSnapshot document) {
                            return new ActivityCard(
                              title: document['title'],
                              type: document['type'],
                              startDateLocal: document['startDateLocal'],
                            );
                          }).toList(),
                        );
                    }
                  },
                )
            );
  }
}

home.dart

...
@override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: 3,
      child: Scaffold(
        appBar: AppBar(
          title: Text("Home"),
          actions: <Widget>[
          ],
          bottom: TabBar(
            tabs: [
              Text("Account"),
              Text("Activity"),
              Text("Links"),
            ],
          ),
        ),
        body: TabBarView(
          children: [
            accountStream(),
            ActivityList(), // now calling a stateful widget in an external file
            linksStream()
            ]
          )
        ),
      );
    }
  }