Flutter Google maps not reloading after changing markers - flutter

Question

I'm working with the google map widget, when I render the map for the first time with static markers it displays all the markers, but when I get the data from API and try to add new markers to the map, it won't display them.
below the code that i'm using :
class Map extends StatefulWidget {
final Position initialPosition;
final List<Marker> allSitesMarkers;
final List<Site> placesSite;
final List<String> mapMarkersCategories;
const Map(this.initialPosition, this.allSitesMarkers, this.placesSite,
this.mapMarkersCategories,
{Key key})
: super(key: key);
#override
State<StatefulWidget> createState() => MapState();
}
class MapState extends State<Map> {
Completer<GoogleMapController> _controller = Completer();
String currentCategoryFilter;
bool filtred = false;
Set<Marker> _markers = Set();
List<Marker> markersToShow;
#override
void initState() {
super.initState();
refreshMarkers();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: (widget.placesSite.isNotEmpty)
? Stack(
children: [
GoogleMap(
initialCameraPosition: const CameraPosition(
target: LatLng(36.798, 10.1717), zoom: 15),
mapType: MapType.normal,
myLocationEnabled: true,
markers: _markers,
onMapCreated: (GoogleMapController controller) {
controller.setMapStyle(
'[ //... ]');
_controller.complete(controller);
},
),
_chips()
],
)
: const NoListMap(),
);
}
Widget _chips() {
//..
}
filterSites(String category) {
setState(() {
_markers.clear();
filtred = true;
markersToShow = widget.allSitesMarkers
.where((element) => element.infoWindow.title == category)
.toList();
});
refreshMarkers();
}
refreshMarkers() {
if (filtred) {
setState(() {
_markers.clear();
_markers.addAll(markersToShow);
});
} else {
setState(() {
_markers.clear();
_markers.addAll(widget.allSitesMarkers);
});
}
}
}
I'm using:
Flutter 2.10.2
Dart 2.16.1
google_maps_flutter : 2.0.9

Answer 1

Your _markers is a Set, and in setState you use clear and addAll to empty it and to add new items to the set. But the value of _markers does not change when you do so, therefore it will not trigger a rebuild.
This happens because _markers holds a reference to the Set (like lists, objects etc.).
You need to assign a new value to _markers to trigger a rebuild, for example:
setState(() {
_markers = markersToShow.toSet();
});
This will actually change the reference kept in _markers.