Flutter + Firestore: listen for document changes

Question

I'm getting multiple documents from firestore with this function:

 getNumbers() async {

    QuerySnapshot snapshot = await Firestore.instance
        .collection('numbers')
        .where("owner", isEqualTo: "${userid}")
        .getDocuments();

    List<myModel> numbersList =
        snapshot.documents.map((doc) => myModel.fromDocument(doc)).toList();

  }

Then I use a listview.builder to show the documents.

But I would like to listen to changes, is that possible without using a streambuilder?

I thought of the solution: listen for changes and replace the document of the list with the new changed document. Is that possible?

Thank you very much!

Answer 1

You can initialize your Firestore stream and call setState each time you got new element, but it's less efficient than using StreamBuilder

class NumberList extends StatefulWidget {
  @override
  _NumberListState createState() => _NumberListState();
}

class _NumberListState extends State<NumberList> {
  //somewhere
  List<MyModel> numbersList = List();


  @override
  void initState() {
    listenNumbers();
    super.initState();
  }

  listenNumbers() {
    Stream<QuerySnapshot> streamNumbers = Firestore.instance
      .collection('numbers')
      .where("owner", isEqualTo: "${userid}")
      .snapshots();

    streamNumbers.listen((snapshot) {
      snapshot.documents.forEach((doc) {
        MyModel obj = MyModel.fromDocument(doc);
        numbersList.add(obj);
        setState(() {

        });
      });
    });
  }


  @override
  Widget build(BuildContext context) {
    return Container(child: ListView.builder(
      itemCount: numbersList.length,
      itemBuilder: (context, index){
        return NumberWidget(
          key: UniqueKey(),
          number: numbersList[index]
        );
      },
    )
    );
  }
}