How to refresh a streamBuilder with firestore in flutter

I am getting lost in managing stream builder... please help!

I have this great class which get data from firestore and present it as a List. The stream include a variable (rag) which can change based on user interaction and I would like that the stream updates when such variable changes. I am not able to make it work and I believe that my issue is that I am not able to refresh the stream. How can I refresh my stream?? In iOS there is a simple reloadData line for that...

See below my code

class RestaurantList extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
      stream: _firestore
          .collection('restaurants')
          .where('lat', isGreaterThan: appData.currentLatitude - rag)
          .where('lat', isLessThan: appData.currentLatitude + rag)
          .snapshots(),
      builder: (context, snapshot) {
        if (snapshot.hasError) return new Text('Error: ${snapshot.error}');
        switch (snapshot.connectionState) {
          case ConnectionState.waiting:
            return Center(
              child: new Text(
                'Loading...',
              ),
            );
          default:
            final restDB = snapshot.data.documents;

              for (var rest in restDB) {
                final restID = rest.documentID;
                final name = rest.data['name'];
                final lati = rest.data['lat'];
                final longi = rest.data['lon'];
                final distance = (appData.currentLatitude - lati) *
                        (appData.currentLatitude - lati) +
                    (appData.currentLongitude - longi) *
                        (appData.currentLongitude - longi);

                if (longi < appData.currentLongitude + rag &&
                    longi > appData.currentLongitude - rag) {
                  final restaurant = Restaurant(
                    restID: restID,
                    name: name,
                    distance: distance,
                    lati: lati,
                    longi: longi,
                  );

                  restaurants.add(restaurant);

                }
              }      

            return ListView(
              shrinkWrap: true,
              physics: ClampingScrollPhysics(),
              children: restaurants,
            );
        }
      },
    );
  }
}