topic Re: How to pan and zoom to selected point correctly? in ArcGIS API for Silverlight Questions

How to pan and zoom to selected point correctly?

AnatoliiTerentiev — Sat, 11 Dec 2021 14:21:22 GMT

Dear Gurus!

Excuse for question, but I can't understand why don't work this block:

 myMap.PanTo(selectedPoint);
 myMap.ZoomToResolution(140, selectedPoint);

when in xaml :

<esri:Map x:Name="myMap"  Extent="3200000,8550000,4250000,10100000">
       <esri:OpenStreetMapLayer ID="OSMLayer" Style="Mapnik" />
      <esri:ArcGISDynamicMapServiceLayer ID="RK" 
                            Url="http://localhost:6080/ArcGIS/rest/services/karelia/MapServer" />
      <esri:FeatureLayer    ID="routes_osm" 
                            Url="http://localhost:6080/ArcGIS/rest/services/karelia/MapServer/1" >                                
                </esri:FeatureLayer>
</esri:Map
>

PanTo - works just as expected, and after the addition of the second line- the result is not clear

Thanks in advance!

Re: How to pan and zoom to selected point correctly?

DominiqueBroux — Fri, 30 Jan 2015 09:49:06 GMT

Due to animation PanTo and ZoomToResolution are asynchronous operations that give undefined results if they are executed simultaneously.

One option may be to create a method that do both actions at the same time (e.g. centerAndZoom method)

Re: How to pan and zoom to selected point correctly?

AnatoliiTerentiev — Fri, 30 Jan 2015 11:20:11 GMT

Excellent, Dominique! That is just what I wanted!

Re: How to pan and zoom to selected point correctly?

AnatoliiTerentiev — Fri, 30 Jan 2015 11:41:24 GMT

And If not difficult - how do likewise for panTo(geometry) (line or polygon)?

Re: How to pan and zoom to selected point correctly?

DominiqueBroux — Fri, 30 Jan 2015 12:38:42 GMT

For panning/zooming to a line or polygon, you have the following options:

- use PanTo if you want to keep the map resolution

- use the former CenterAndZoom with geometry.Extent.GetCenter() if you want to zoom at a predefined resolution (but not sure the full geometry will be inside the map extent)

- or most simple, use ZoomTo(geometry) or something like ZoomTo(geometry.Expand(1.2))

Re: How to pan and zoom to selected point correctly?

AnatoliiTerentiev — Fri, 30 Jan 2015 12:55:01 GMT

It's clear, but there were doubts that there is a certain algorithm for computing the resolution depending on the size of the object.

Re: How to pan and zoom to selected point correctly?

AnatoliiTerentiev — Sat, 11 Dec 2021 14:21:25 GMT

When I tried to get initial state of the map as follows

        private void setInitialMap()
        {
            centerAndZoom(myMap, initCentrPoint, InitMapResolution);
            Thread.Sleep(100);
        }

        private void centerAndZoom(ESRI.ArcGIS.Client.Map map, ESRI.ArcGIS.Client.Geometry.MapPoint mapPoint, double resolution)
        {
            double ratio = 1.0;
            if (map.Resolution != 0.0)
                ratio = resolution / map.Resolution;


            if (ratio == 1.0)
                map.PanTo(mapPoint);
            else
            {
                ESRI.ArcGIS.Client.Geometry.MapPoint mapCenter = map.Extent.GetCenter();
                double X = (mapPoint.X - ratio * mapCenter.X) / (1 - ratio);
                double Y = (mapPoint.Y - ratio * mapCenter.Y) / (1 - ratio);
                map.ZoomToResolution(resolution, new ESRI.ArcGIS.Client.Geometry.MapPoint(X, Y));
            }
        }

the result was negative, as long as I do not put a slight delay 100 ms. What may be the reason?