topic Re: Legend Widget -- Layers added dynamically in ArcGIS JavaScript Maps SDK Questions

Legend Widget -- Layers added dynamically

GregKnight — Tue, 29 Jan 2013 23:21:58 GMT

Hi all,

Are there any examples out there that illustrate the logic associated with using the Legend Dijit with layers that are added to the map after the map is instantiated? All the examples seem to focus on displaying legends for layers that are known at runtime. In my application the layers are not necessarily known at runtime. Specifically, I am having some difficulty with the logic associated with

1) initializing the legend at runtime when its possible that no operational layers are loaded

and

2) later refreshing (or starting) the legend with (ad-hoc) operational layers that are added after the map is initially loaded

Are there any examples out there of this nature? If not, could someone provide an outline of the logic necessary here?

Many thanks,
Greg

Re: Legend Widget -- Layers added dynamically

ShreyasVakil — Wed, 30 Jan 2013 00:01:10 GMT

I don't know if you have already seen this sample, but it does update the legend dynamically when we update the visibility of layers.
Legend - toggle services

Re: Legend Widget -- Layers added dynamically

GregKnight — Sun, 12 Dec 2021 04:46:58 GMT

Hi Shreyas,

Yes, I have seen that sample. In that sample, the layers are known at runtime however -- and their layerInfo is pushed into an object which is passed to the legend dijit when it is instantiated.

var quakeLayer = new esri.layers.ArcGISDynamicMapServiceLayer("http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Earthquakes/EarthquakesFromLastSevenDays/MapServer",{id:'quakes'});
legendLayers.push({layer:quakeLayer,title:'Earthquakes'});
var fireLayer = new esri.layers.ArcGISDynamicMapServiceLayer("http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Fire/Sheep/MapServer",{id:'fire'});
legendLayers.push({layer:fireLayer,title:"Fire"});

Functionally, this is similar to what Im looking for, but I dont have the luxury of knowing the layerInfo at runtime. What would I do in this case?

Many thanks,
Greg

BTW - I love the updates to the JS API pages... fantastic!

Re: Legend Widget -- Layers added dynamically

KellyHutchins — Wed, 30 Jan 2013 21:46:35 GMT

Hi Greg,

The legend widget has a refresh property that you can use to update it with new layer information. Here's an example that shows how to refresh the legend with new layer info.

http://jsfiddle.net/vguu3/

Re: Legend Widget -- Layers added dynamically

GregKnight — Thu, 31 Jan 2013 12:31:36 GMT

Hi Kelly,

That definitely helps. Ill revisit my code later today.

Thank you,
Greg