How to determine which marker was pressed on the map - google-maps

Question

I am unable to determine which marker was tapped by the user on Google maps. I've added onTap: _onMarkerTapped(MarkerId markerId) event where I try to open another page with a more detailed Google Map based on which marker user has tapped. When I add bunch of markers (as a Set of markers) to my Google map, I do use unique markerId and that's what I pass in as an argument to a private custom method _onMarkerTapped(). The issue is, inside thsi event I always ended up getting the last markerId i.e. the last marker which I added to the Set. Is there any way to get the current markerid which user has tapped?
add onTap event handler for every marker I added in a set of Markers
for (var campusData in Campuses.campusLocations) {
campusDetails = json.decode(campusData);
campus = Campus.fromJson(campusDetails);
markerId = MarkerId(i.toString());
mrkr = new Marker(
markerId: markerId, // a string for marker unique id
icon: BitmapDescriptor.fromAsset(
'assets/wsu#2x.png'), // options for hues and custom imgs
position:
LatLng(campus.latitude, campus.longitude), // lat and long doubles
onTap: () {
_onMarkerTapped(markerId);
});
campusMarkers.add(mrkr);
i++;
}
return GoogleMap(
initialCameraPosition: cameraPosition,
onMapCreated: _onMapCreated,
mapType: MapType.normal,
markers: campusMarkers,
onTap: (lng) => _onMapTapped(lng),
);
void _onMarkerTapped(MarkerId markerId) {
final Marker tappedMarker = campusMarkers.elementAt(int.parse(markerId.value));
if (tappedMarker != null) {
}
else{
print("Tapped marker is NULL..");
}
}
Looking for ways to determine which marker was tapped by the user

Answer 1

Pay attention to these two line:
markerId = MarkerId(i.toString());
...
onTap: () {
_onMarkerTapped(markerId);
}
You are not creating a uniqueMarkerId for each loop, you are just reassigning it, so the last one you assigned will always be used by _onMarkerTapped(markerId). To fix this, use:
final markerId = MarkerId(i.toString());

Answer 2

For anyone who come across this issue, please follow the code example at https://github.com/flutter/plugins/blob/master/packages/google_maps_flutter/example/lib/place_marker.dart .. especially the _add() method and _onMarkerTapped() methods. PLEASE make sure to use a Map to declare your set of markers e.g. Map<MarkerId, Marker> markers = <MarkerId, Marker>{};