topic How to get lat/long from drag event in ArcGIS JavaScript Maps SDK Questions

How to get lat/long from drag event

BorjaCanseco — Sat, 11 Dec 2021 12:38:02 GMT

Hello!

I'm using the Esri JS API version 4.2 with angular-esri-map and I'm working with a 2D map.

I notice that the default behavior for when a user holds Shift and then clicks+drags on the map is that a rectangular bounding box is drawn, which then becomes the bounds of the view when the user lets go.

I'm trying to implement a new behavior in which doing the same thing but with the CTRL key instead of Shift will simply draw a rectangular box on the map without changing the view, and then store the latitude and longitude of both the Northwest and Southeast corners in some JavaScript variables (in my case, variables tied to my angularjs controller).

My question: How do I get lat/long from this? I'm only able to see x/y from both the origin and destination points using the drag event.

$ctrl.onViewCreated = function(view) {
    $ctrl.mapView = view;

    $ctrl.mapView.on('click', function(e) {
      $ctrl.clickCoordinates = {
        lat: e.mapPoint.latitude,
        lng: e.mapPoint.longitude,
      };
      // I can get lat/long here...
    });

    $ctrl.mapView.on('drag', ['Ctrl'], function(e) {
      // ...but not here!
      e.stopPropagation();
    });
};‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Thanks!

Re: How to get lat/long from drag event

RobertScheitlin__GISP — Mon, 30 Jan 2017 16:52:26 GMT

Borja,

A click event has a mapPoint property but a drag event does not. The drag event does though has a origin property (in screen coordinates) and both x and y. so you just convert those screen coordinates and the x and y to get your drag bounds.

https://developers.arcgis.com/javascript/latest/api-reference/esri-views-MapView.html#event:drag

Re: How to get lat/long from drag event

BorjaCanseco — Mon, 30 Jan 2017 20:37:00 GMT

Thanks for the reply, Robert!

Could you point me in the right direction for conversion? I found a webMercatorUtils service but it seems like the .xyToLngLat() method returns strange values - probably because the map I'm working with isn't a WM projection?

Would I need to use the GeometryService instead?

Re: How to get lat/long from drag event

RobertScheitlin__GISP — Mon, 30 Jan 2017 20:40:08 GMT

Borja,

The values you will be receiving are in screen coordinates and thus have to be converted to map coordinates, so you use the views toMap method:

https://developers.arcgis.com/javascript/latest/api-reference/esri-views-MapView.html#toMap