Updating restaurant locations when map position moves - flutter

Question

This code successfully shows nearby restaurants using Google Places API based on my current location. When I manually move the map position on my phone, though, new restaurant markers do not show in the new location of the map. Below is my code. I also have commented out something I was trying to do to update the markers to the new camera position. I used onCameraMove in the Google Maps. Any help with updating new restaurant markers based on the new camera position is greatly appreciated.
import 'package:family_farms_forever/utilities/secrets.dart';
import 'package:flutter/material.dart';
import 'package:geolocator/geolocator.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:google_maps_webservice/places.dart';
import 'package:google_maps_flutter_platform_interface/src/types/marker_updates.dart';
void main() => runApp(const MyApp());
final places = GoogleMapsPlaces(apiKey: Secrets.iosApiKey);
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
return MaterialApp(
title: "Market Map",
home: Scaffold(
// We'll change the AppBar title later
appBar: AppBar(title: const Text("My Location")),
body: const MyMarketMap()),
);
}
}
class MyMarketMap extends StatefulWidget {
const MyMarketMap({super.key});
#override
State<StatefulWidget> createState() {
return _MyMarketMapState();
}
}
class _MyMarketMapState extends State<MyMarketMap> {
late Future<Position> _currentLocation;
late final Set<Marker> _markers = {};
#override
void initState() {
super.initState();
_currentLocation = Geolocator.getCurrentPosition();
}
Future<void> _retrieveNearbyRestaurants(LatLng userLocation) async {
PlacesSearchResponse response = await places.searchNearbyWithRadius(
Location(lat: userLocation.latitude, lng: userLocation.longitude),
10000,
type: "restaurant");
Set<Marker> restaurantMarkers = response.results
.map((result) => Marker(
markerId: MarkerId(result.name),
// Use an icon with different colors to differentiate between current location
// and the restaurants
icon: BitmapDescriptor.defaultMarkerWithHue(
BitmapDescriptor.hueAzure),
infoWindow: InfoWindow(
title: result.name,
snippet:
"Ratings: ${result.rating?.toString() ?? "Not Rated"}"),
position: LatLng(
result.geometry!.location.lat, result.geometry!.location.lng)))
.toSet();
setState(() {
_markers.addAll(restaurantMarkers);
});
}
#override
Widget build(BuildContext context) {
return FutureBuilder(
future: _currentLocation,
builder: (context, AsyncSnapshot snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasData) {
// The user location returned from the snapshot
Position snapshotData = snapshot.data;
LatLng userLocation =
LatLng(snapshotData.latitude, snapshotData.longitude);
if (_markers.isEmpty) {
_retrieveNearbyRestaurants(userLocation);
}
// void upDateMarkers() {
// Set<Marker> updatedMarkers =
// {}; //new markers with updated position go here
// updatedMarkers = {};
// /// Then call the SetState function.
// /// I called the MarkersUpdate class inside the setState function.
// /// You can do it your way but remember to call the setState function so that the updated markers reflect on your Flutter app.
// /// Ps: I did not try the second way where the MarkerUpdate is called outside the setState buttechnically it should work.
// setState(() {
// MarkerUpdates.from(Set<Marker>.from(_markers),
// Set<Marker>.from(updatedMarkers));
// _markers = updatedMarkers;
// _markers.addAll(updatedMarkers);
// //swap of markers so that on next marker update the previous marker would be the one which you updated now.
// // And even on the next app startup, it takes the updated markers to show on the map.
// });
// }
return GoogleMap(
myLocationEnabled: true,
zoomGesturesEnabled: true,
//onCameraMove: (position) => upDateMarkers(),
initialCameraPosition: CameraPosition(
target: userLocation,
zoom: 12,
),
markers: _markers
..add(Marker(
markerId: const MarkerId("User Location"),
infoWindow: const InfoWindow(title: "User Location"),
position: userLocation)),
);
} else {
return const Center(child: Text("Failed to get user location."));
}
}
// While the connection is not in the done state yet
return const Center(child: CircularProgressIndicator());
});
}
}

Answer 1

You have to use Stream for getting updates :
StreamBuilder<Position>(
stream: Geolocator.getPositionStream(
locationSettings: LocationSettings()
),
builder: (context, snapshot) {
... Do your Rest Coding Here...
You can control the behavior of the stream by specifying an instance of the [LocationSettings] class for the [locationSettings] parameter. Standard settings are:
LocationSettings.accuracy: allows controlling the precision of the position updates by supplying (defaults to "best");
LocationSettings.distanceFilter: allows controlling the minimum distance the device needs to move before the update is emitted (default value is 0 which indicates no filter is used);
LocationSettings.timeLimit: allows for setting a timeout interval. If between fetching locations the timeout interval is exceeded a [TimeoutException] will be thrown. By default no time limit is configured.