flutter_firestore_tut

.\lib\scr\home.dart

//...
class _Home extends State<StatefulWidget> {
  //...
  @override
  void initState() {
    super.initState();
    _transactionListener = Firestore.instance
        .collection('stats')
    .document('interactions')
        .snapshots()
        .listen((data) => transactionListenerUpdate(data));
  }

  void transactionListenerUpdate(data) {
    var number = data['count'];
    setState(() {
      _interactionCount = number;
    });
  }
  //...
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      //...
  }
}