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zoom to extent of a layer in a Map Service

SebastianRoberts

I thought this would be easy, but I can't figure out how to zoom to the extent of a layer in a map Service (not the extent of the entire map service). In the Flex API there is a layerDetails class, but I can't find anything similar in JavaScript.

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Accepted answers

BenFousek

Check out http://dojotoolkit.org/reference-guide/1.7/dojo/io/script.html#dojo-io-script

All my apps are module based, pulling snippets and code from my server; consequently I make a ton xhrGet and xhrPost requests and have always used a proxy. I'm in the process of converting all my apps to dojo 1.7 in anticipation of jsapi v3, and will be doing more with io-script.

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Anonymous User

Are you referring to zooming into the extent of a specific layer within the MapService, for instance:

http://server.arcgisonline.com/ArcGIS/rest/services/Demographics/USA_Diversity_Index/MapServer/1

If so, you could just zoom into that particular layer's extent and not the map service's extent. There is a DynamicLayerInfo class, too. You could get the map service's sublayers and ultimately their extent.

SebastianRoberts

Yes that is what I am referring to, but I am having trouble getting the extent of an individual layer. I have an ArcGISDynamicServicLayer and I know the layer number of the layer that I want to zoom to, but I dont' know how to get its extent.

By the way, I tried setting a variable equal to the dynamicLayerInfos property of my ArcGISDynamicServicLayer, but the resulting variable has a value of undefined. However, even if I did get an array of LayerInfos, the LayerInfo class doesn't seem to have an extent property, so I don't know if that will helpful.

resultsLayer = new esri.layers.ArcGISDynamicMapServiceLayer(serviceURL, {id: "resultsLayer"});
        map.addLayer(resultsLayer);
layer = resultsLayer.dynamicLayerInfos

SebastianRoberts

I found a kludgy solution, but I know there must be a better way. I create a featureLayer for the layer in the map service. FeatureLayer has a fullExtent property. However, the fullExtent property doesn't exist immediately after the featureLayer is first created. If I do a selection on the Layer, then the property exists. Therefore, I do a selection (using a where clause that I know won't select any features), and in the callback I can zoom to the layer.

     zoomLayer = new esri.layers.FeatureLayer(serviceURL+layernum);
     var query = new esri.tasks.Query();
     query.where = "0=1";
     zoomLayer .selectFeatures(query,esri.layers.FeatureLayer.SELECTION_NEW,zoomSel);
}
.........

function zoomSel(){
        map.setExtent(zoomLayer.fullExtent);
}

BenFousek

Individual layers in a map service have an extent but I don't see where dynamic layer creates an object for for it. You could always make a rest call to the layer and get it's extent:

var getLayerExtent = dojo.xhrGet({
   url: 'http://MY_URL/ArcGIS/rest/services/MY_MAP_SERVICE/MapServer/0?f=json',
   handleAs: 'json',
   load: function(r) {
       var extent = r.extent;
       //zoom to it
   }
);

JohnnyPenet

Did you try to get the information when the layer has been loaded? You can do this in the following way :

                mapLayer = new esri.layers.ArcGISDynamicMapServiceLayer(layerUrl,
    { id: layerName,
        visible: visible
    });
                handle = dojo.connect(mapLayer,"onLoad", function (layer) {
                    dojo.disconnect(handle);
                    ... Do the extent processing here
                });

BenFousek

When you add a dynamic layer the api makes a rest call to the map service (http://MY_URL/ArcGIS/rest/services/MY_MAP_SERVICE/MapServer?f=json) which includes sub-layer information but not detailed sub-layer info like extent. The only way to get a sub-layer's extent to to make some some kind of rest call on said sub-layer (http://MY_URL/ArcGIS/rest/services/MY_MAP_SERVICE/MapServer/0?f=json). Creating a feature layer is one way, but a lot of work just to get the extent.

SebastianRoberts

I think Ben is right, you can't get the extent of sublayers from the ArcGISDynamicMapServiceLayer object. Ben, your solution is much more elegant than mine, but when I tried it I ran into crossdomain issues when trying to make the dojo.xhrGet call since my webserver is not the same as my ArcGIS server. It seems I would need to set up a proxy on my webserver in order to make the rest call, but somehow the ArcGIS JavaScript api gets around this and makes rest calls.

BenFousek

SebastianRoberts

Ben, Thanks for your help. Using dojo.script.io (JSONP) worked. Below is the resultant code. For some reason I couldn't use the data.extent object directly, but had to create a new object.

dojo.io.script.get({
    url: queryURL+layernum+'?f=json',
    content: {q: "#dojo"},
    callbackParamName: "callback"
}).then(function(data){   
      var newExtent = new esri.geometry.Extent
      newExtent.xmax = data.extent.xmax;
      newExtent.xmin = data.extent.xmin;
      newExtent.ymax = data.extent.ymax;
      newExtent.ymin = data.extent.ymin;
      map.setExtent(newExtent);
   });
}

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