Flutter: Provider and how to update records from the DB in the background - flutter

Question

I am new to Flutter and I have this simple use case: in my Cloud Firestore DB I have a list of JSON representing events. I want to show them through my Flutter app in a ListView.
My requirements is that the ListView doesn't refresh in real-time but only when a pull-on refresh (implemented using RefreshIndicator) is done by the user or when the app resumes from background
I tried to implement this in 2 ways (I am using provider package for state management):
Using StreamProvider to create a stream of records from the DB. This continuosly updates the list view (basically the widget changes while the user is looking at it and I don't want this)
Using a ChangeNotifierProvider that refers to a EventManager class which holds a List<Event>. This class has a pull method which updates its internal state. I call this method when the user does the pull-on refresh (in the onRefresh callback of RefreshIndicator).
Option 2 seems to work well however I do not know how to implement the refresh when the app resumes from background. As I said I am using provider (and therefore StatelessWidget) and apparently there is no way to bind to these events when using StatelessWidgets
Do you have any suggestions and best practices for this use case?

Answer 1

You need to access Flutters lifecycle methods and fire a callback when the app resumes.
You can add a stateful widget with WidgetsBindingObserver and put that somewhere in the scope of your Provider, but as a parent of whatever widget you use to display the info.
Or you can make your PullToRefresh widget stateful and do the same thing.
class LifeCycleWidget extends StatefulWidget {
#override
_LifeCycleWidgetState createState() => _LifeCycleWidgetState();
}
class _LifeCycleWidgetState extends State<LifeCycleWidget>
with WidgetsBindingObserver {
AppLifecycleState _appLifecycleState;
#override
void initState() {
super.initState();
WidgetsBinding.instance.addObserver(this);
refreshOnResume();
}
#override
void didChangeAppLifecycleState(AppLifecycleState state) {
setState(() {
_appLifecycleState = state;
});
refreshOnResume();
}
void refreshOnResume() {
if (_appLifecycleState == AppLifecycleState.resumed) {
print('resumed');
// your refresh method here
}
}
#override
Widget build(BuildContext context) {
return HomePage();
}
}
Add the following to your main method if it's not there already.
WidgetsFlutterBinding.ensureInitialized();
Another way to do it without adding a stateful widget would be with GetX. You can still keep all your Provider stuff but only use the SuperController which provides lifecycle methods. This I can't test because I don't have your Provider code but you can probably get away with creating the class below and initializing the controller somewhere within the scope of the relevant Provider widget with
Get.put(LifeCycleController());
Then call the function in the onResumed override and you can use Get.context if you need context.
class LifeCycleController extends SuperController {
#override
void onDetached() {
debugPrint('on detached');
}
#override
void onInactive() {
debugPrint('on inactive');
}
#override
void onPaused() {
debugPrint('on pause');
}
#override
void onResumed() {
// your refresh function here. Access context with Get.context
debugPrint('on resume');
}
}