How to retain data while using ScopedModel in Flutter? - flutter

Question

I am using ScopedModel to fetch some data from a Firebase database.
I am fetching a list of events.
I fetch the events from the endpoint inside the Model;
I store the events into a List<Event> inside the model;
I use that list to build my ListView.
mixin EventModel on Model {
List<Event> _events = [];
Future<http.Response> fetchEvents() async {
http.Response response = await http.get(//Url);
final List<Event> fetchedEvents = [];
... // decode response data into fetchedEvents
// Add the loaded data to my List
_events = fetchedEvents;
notifyListeners();
...
}
}
So, when opening the EventsPage the first thing I do is to fetch the data in initState().
class _EventPageState extends State<EventPage> {
#override
void initState() {
super.initState();
widget.model.fetchEvents();
}
}
}
After fetching the network data, my List inside my app has the network data so I can use it to build my ListView.
EventsPage.dart
Widget _buildListView(MainModel model) {
return Center(
child: ListView.builder(
itemBuilder: (BuildContext context, int index) {
return ItemEventBig(model.events[index], index);
},
itemCount: model.events.length,
),
);
}
My problem is that, if I navigate to another page and then come back to EventsPage, initState() will be called again, so fetchEvents. Making the app reload all the events list again.
I would like to retain the downloaded data while my app is alive, so If the user go and come back to EventsPage the data will not be lost.
I was used to do it in Android using ViewModel, how to do it in Flutter?
I want to keep using ScopedModel to do my State Management in Flutter.
Possible Solution
I thought that a solution would be to store the events in a List<Event> as I am doing. Then, when calling fetchEvents() I could first check if my List<Event> is not null if so, I don't need to call it again because data was already loaded.
This seems a bad solution for me, especially when I have multiple pages fetching the data. Suppose I load the first one, when I go to the second one it will assume the data was already loaded because List<Event> is non null and it will not load again.

Answer 1

See Flutter Documentation - https://api.flutter.dev/flutter/widgets/AutomaticKeepAliveClientMixin-mixin.html
class _EventPageState extends State<EventPage>
with AutomaticKeepAliveClientMixin<EventPage> {
#override
void initState() {
super.initState();
widget.model.fetchEvents();
}
}
#override
// TODO: implement wantKeepAlive
bool get wantKeepAlive => true;
}