Adding markers dynamically to flutter google map

问题

I'm using Flutter to make a mobile application that uses a map. We decided to use Google map and the plugin for flutter we use is:

google_maps_flutter: ^0.5.7

I understand that adding markers to the map works like this:

Map<MarkerId, Marker> markers = <MarkerId, Marker>{};
Marker _marker = new Marker(
  icon: BitmapDescriptor.defaultMarker,
  markerId: _markerId,
  position: LatLng(34.024441,-5.0310968),
  infoWindow: InfoWindow(title: "userMarker", snippet: '*'),
);
GoogleMap _map;

@override
void initState(
   markers[_markerId] = _marker;
   _map = new GoogleMap(
    /* other properties irrelevant to this prob */
    markers: Set<Marker>.of(_markers.values),
  );
);

The above snippet does work, I get to see the marker on the map. But modifying the marker or trying to add another marker like in the snippet below does not work.

FloatingActionButton(
    onPressed: () {
      setState(() {
        _marker = new Marker(
            icon: BitmapDescriptor.defaultMarker,
            markerId: _markerId,
            position: LatLng(currentLocation.latitude, currentLocation.longitude),
            infoWindow: InfoWindow(title: "userMarker", snippet: '*'),
            onTap: () {
              debugPrint("Marker Tapped");
            },
          );
        markers[_markerId] = _marker; // What I do here is modify the only marker in the Map.
      });
      markers.forEach((id,marker) { // This is used to see if the marker properties did change, and they did.
        debugPrint("MarkerId: $id");
        debugPrint("Marker: [${marker.position.latitude},${marker.position.longitude}]");
      });
    });
)

My intention here is using another plugin (geoLocator) to get location data of the user and change the only marker I have so it can track his movements. The debugPrint shows that the data is indeed changing, but I see no change in the map (the initial marker that I change uses a different location than my own when I test).

回答1:

If there's no specific reason for you to use Map data structure, here's what I've done in the past.

I have a Set of Marker in my State

Set<Marker> markers = Set();

Give it to the map widget. markers: markers

GoogleMap(
  onMapCreated: _onMapCreated,
  myLocationEnabled: true,
  initialCameraPosition:
    CameraPosition(target: LatLng(0.0, 0.0)),
  markers: markers,
)

And then adding the Marker, which I'm building with search result and which you'll be building with your user's location, to Set of Marker in setState method.

// Create a new marker
Marker resultMarker = Marker(
  markerId: MarkerId(responseResult.name),
  infoWindow: InfoWindow(
  title: "${responseResult.name}",
  snippet: "${responseResult.types?.first}"),
  position: LatLng(responseResult.geometry.location.lat,
  responseResult.geometry.location.lng),
);
// Add it to Set
markers.add(resultMarker);

Edit: I've just noticed you're using GoogleMap widget in your initState, you need to move it to the build method if you want to rebuild it everytime with the new state values.

来源：https://stackoverflow.com/questions/55987785/adding-markers-dynamically-to-flutter-google-map

标签

google-maps

Flutter

google-maps-markers