topic Re: GeoRSSLayer capture collection changed in ArcGIS API for Silverlight Questions

GeoRSSLayer capture collection changed

GregLutz — Thu, 13 Sep 2012 19:55:06 GMT

Hi, I'm using GeoRSSLayer and I dynamically change the Source URI at runtime. I'm trying to capture when the Graphics.CollectionChanged. But it's not working. Here is my code:

On page load:

GeoRssLayer rssLayer = map1.Layers["GeoRSSLayer"] as GeoRssLayer;             rssLayer.Graphics.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(Graphics_CollectionChanged);

In button click event:

GeoRssLayer rssLayer = map1.Layers["GeoRSSLayer"] as GeoRssLayer;                 rssLayer.ClearGraphics();                 rssLayer.Source = new Uri(source); // source is a new feed url                 rssLayer.Update();

Unfortunately, even though the graphics get updated successfully (I can watch during debug they go from 20 to 0, to 20, to 0, etc). the CollectionChanged event NEVER fires. I need to call ZoomTo method after the graphics layer is updated to zoom in wherever graphics are. If you have any other suggestions on how to perform a ZoomTo after the Source URI changes on a GeoRSSLayer that would work. Of course I can't just simply call ZoomTo in my code after I set the Source because it's asynchronous and I don't see any Completed type events on the GeoRSSLayer to know when it's done loading.

 void Graphics_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)         {             GeoRssLayer rssLayer = map1.Layers["GeoRSSLayer"] as GeoRssLayer;             map1.ZoomTo(rssLayer.FullExtent);         }

Re: GeoRSSLayer capture collection changed

DominiqueBroux — Fri, 14 Sep 2012 06:12:50 GMT

AS you assign a new collection of graphics, you can subscribe to rssLayer.PropertyChanged and, in the Handler, test that the changed property is called "Graphics".

Re: GeoRSSLayer capture collection changed

GregLutz — Fri, 21 Sep 2012 19:45:56 GMT

Thank you, this does answer my question. Unfortunately it doesn't resolve my entire issue, but i'll create a new thread since the issue is unrelated now to the topic.

Re: GeoRSSLayer capture collection changed

GregLutz — Fri, 21 Sep 2012 19:58:10 GMT

Ok, I figured out my Zooming issue works if I listen for the FullExtent property to change, not the Graphics. I was afraid this code would result in an infinite loop (I thought ZoomTo changes the FullExtent property of the map control) but it apparently doesn't.

GeoRssLayer rssLayer = map1.Layers["GeoRSSLayer"] as GeoRssLayer; rssLayer.PropertyChanged += new System.ComponentModel.PropertyChangedEventHandler(rssLayer_PropertyChanged);

void rssLayer_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) {     if (e.PropertyName == "FullExtent")     {         GeoRssLayer rssLayer = map1.Layers["GeoRSSLayer"] as GeoRssLayer;         map1.ZoomTo(rssLayer.FullExtent);     } }

Hopefully this won't result in other problems zooming in every time the full extent property changes. If I just listen for Graphics to change, then the ZoomTo method does not work. Probably because the Graphics layer hasn't updated its layout at that moment yet.