main.dart

body: StreamBuilder(
    stream: dbRef.onValue,
    builder: (context, AsyncSnapshot<Event> snapshot) {
        if (snapshot.hasData) {
        lists.clear();
        DataSnapshot dataValues = snapshot.data.snapshot;
        Map<dynamic, dynamic> values = dataValues.value;
        values.forEach((key, values) {
            lists.add(values);
        });