Getting screen point by latlng of the map.

[softmarshmallow]

I'm trying to implement super animated marker, which cannot done with mapbox marker (symbol).
I have to display flutter widget on different layer than inside the map, but it should look sticked to the specific latlng (obviously,).
on fullscreen map, how can i get the screen position of specific latlng, and get it by event or etc in order to update the marker widget's position on the screen?

it can done on mapbox web, i'm not sure such callback / feature is implemented on this project.

thanks!!

[softmarshmallow]

https://github.com/softmarshmallow/flutter-mapbox-gl
working on here, one more question is, how to get map location changed event?

[m0nac0]

@softmarshmallow #380 adds methods to convert between screen coordinates and geographic coordinates.
MapboxMapController is a ChangeNotifier, so you can subscribe to it and get notified when the cameraPosition property changes. Also see https://pub.dev/documentation/mapbox_gl/latest/mapbox_gl/MapboxMapController-class.html.
I personally think a separate callback would be nice, as MapboxMapController also notifies its listeners on changes to some other properties.

[m0nac0]

@softmarshmallow Also, I'd be very interested to hear if you manage to achieve a good performance with your approach, as I haven't tried this myself.

[softmarshmallow]

@m0nac0 Oh.. LOL i was working on the samethig.

[softmarshmallow]

#407 (comment)

i don't see any updates related to map movement callback @m0nac0

[m0nac0]

This is what I meant:

MapboxMapController is a ChangeNotifier, so you can subscribe to it and get notified when the cameraPosition property changes. Also see https://pub.dev/documentation/mapbox_gl/latest/mapbox_gl/MapboxMapController-class.html.

The cameraPosition describes what is visible on the map.

[softmarshmallow]

@m0nac0
as descirbed here, #407

I was saying adding listener on controller won't work as expected. it only gets called on start/end of the camera movement

[m0nac0]

@softmarshmallow Ah sorry, I misunderstood that. Have you tried listening to isCameraMoving and as long as that's true checking for a newcameraPosition?

[softmarshmallow]

How exactly can i "listen" to isCameraMoving ? it's just a property, not observable. use a loop? (seems alot dangerous)

[softmarshmallow]

  @override
  void initState() {
    super.initState();
    widget.controller.addListener(() {
      print("updated");

      if (controller.isCameraMoving) {
        startUpdate();
      } else {
        stopUpdate();
      }

      //          controller.
//          cameraPosition = controller.cameraPosition;
//          print("cameraPosition.bearing : ${cameraPosition.bearing}");
//          print("cameraPosition.tilt : ${cameraPosition.tilt}");
//          print("cameraPosition.target : ${cameraPosition.target}");
//          print("cameraPosition.zoom : ${cameraPosition.zoom}");
      controller.toScreenLocation(LatLng(0, 0)).then((value) {
        print("screen point: $value");
        setState(() {
          point = value;
        });
      });
      controller.getVisibleRegion().then((value) {
//            setState(() {
        visibleRegion = value;
//            });
      });
    });
  }

  bool isUpdating;

  startUpdate() async {
    isUpdating = true;
    while (isUpdating) {
      print("point!!");
      final newp = await controller.toScreenLocation(LatLng(0, 0));
      setState(() {
        point = newp;
      });
    }
  }

  stopUpdate() {
    isUpdating = false;
  }

not getting the performance i want TT..

marker follows late by apx. 15 fps

i think toScreenPoint should be implmeneted with dart nativly, the latency is crazy. not usable for live updates.

[m0nac0]

How exactly can i "listen" to isCameraMoving ? it's just a property, not observable. use a loop? (seems alot dangerous)

Just like with the cameraPosition property; MapboxMapController will notify its listeners also on changes to the isCameraMoving property.

[softmarshmallow]

How exactly can i "listen" to isCameraMoving ? it's just a property, not observable. use a loop? (seems alot dangerous)

Just like with the cameraPosition property; MapboxMapController will notify its listeners also on changes to the isCameraMoving property.

tried it, cannot get the desired performance.

related: #408

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[teganscott]

@softmarshmallow did you ever have any success with a super animated marker? Currently I am working on implementing a similar solution as you described above but am concerned about the performance hits. Thanks!