topic Re: JSON to LayerLegendInfo in ArcGIS API for Flex Questions

JSON to LayerLegendInfo

AndrewHaigh — Thu, 16 Dec 2010 12:53:13 GMT

I'm wondering what the best way is to convert the results of the ArcGIS Server 10 SP1 Legend request into an array of LayerLegendInfo for an ArcGISDynamicMapServiceLayer.

Is there a smart way I can do it or is it just a mater of iterating through the object returned by the HTTP Service?

I did try and specify a format of AMF onto the legend request but it comes back as not supported.

Thanks

Andrew

Re: JSON to LayerLegendInfo

DasaPaddock — Thu, 16 Dec 2010 20:20:17 GMT

You can call getLegendInfos() on the 3 layers that implement the ILegendSupport interface and your responder will get an Array of LayerLegendInfo instances:
http://help.arcgis.com/en/webapi/flex/apiref/com/esri/ags/layers/ILegendSupport.html

Re: JSON to LayerLegendInfo

AndrewHaigh — Sat, 11 Dec 2021 22:41:17 GMT

Dasa,

Thanks for your feedback on this, I did come accross the ILegendSupport interface after I posted this but have only just had time to look into it.

I think I have written some code which should work however, I seem to be getting a rather unexpected result.

Note that I'm using ArcGIS Server 10.0 Service Pack 1 (Microsoft .Net Framework Edition) with ArcGIS API for Flex version 2.2.2010-12-08 on a secure network (i.e. no internet access).

Here's the code, which is invoked once the ArcGISDynamicMapServiceLayer has completed initialisation.

protected function referenceDataLayerInitComplete(event:FlexEvent):void
{
 // Note that referenceDataMapLayer is an ArcGISDynamicMapServiceLayer from 10.0 SP1
 var token:AsyncToken = referenceDataMapLayer.getLegendInfos(null);
 var responder:mx.rpc.Responder = new mx.rpc.Responder(getLegendResult, getLegendFault);
 token.addResponder(responder);
}

public function getLegendResult(obj:Object):void
{
 trace("We have a result");
}

public function getLegendFault(obj:Object):void
{
 trace("We have an error");
}

Everytime I invoke the code I get a HTTP error because it appears as though the getLegendsInfos is always sending the request to http://www.arcgis.com/sharing/tools/legend - which fails because there is no internet connection.

I have checked the service info returned for the ArcGISDynamicMapServiceLayer and it is returning the correct version of 10.01 so I would expect it to access the local rest endpoint for the legend.

Have i done something wrong or is this a bug.

Thanks

Andrew

Re: JSON to LayerLegendInfo

AndrewHaigh — Fri, 17 Dec 2010 08:09:32 GMT

Hmm,

Odd, I seem to have discovered that this works ok but my problem was actually down to an issue with a stale capabilities response been cached by the browser.

Oh all working fine now.

Re: JSON to LayerLegendInfo

DanielBradshaw — Wed, 04 May 2011 23:02:15 GMT

A bit old... but what capability were you missing? I have Map, Query, Data but am seeing the same issue you described. All getLegendInfos calls always route through the www.arcgis.com which completely fails if my local map service isn't externally accessible.

Re: JSON to LayerLegendInfo

AndrewHaigh — Thu, 05 May 2011 05:55:45 GMT

Well I'm not totally sure what I did to fix the problem, if I'm honest but here are the steps I completed which seemed to solve the problem:

1. Clear the ArcGIS Server Rest Services Cache (http://server/ArcGIS/rest/admin)

2. Clear the browser Cache

I suspect it was the first change which resolved the problem, but you should be able to check access to the legend via http://server/ArcGIS/rest/services/MapServiceName/MapServer/legend.

Hope this helps

Andrew

Re: JSON to LayerLegendInfo

JasonTrimble — Thu, 05 May 2011 15:27:19 GMT

I too am having the same issue. My arcgis server is at version 10.01, but when my flex app attempts to call getLegendInfos on a layer the requests is trying to go through arcgis.com to get legend information.
I can view the JSON response for my service through the rest legend endpoint in my browswer, so that seems to be working.
Why are flex calls trying to go through arcgis.com.

I have cleared the rest cache, and my browswer cache, neither of those resolved the issue.

Re: JSON to LayerLegendInfo

DanielBradshaw — Thu, 12 May 2011 16:44:53 GMT

I'm with Jason... cleared every concievable cache possible and the getLegendInfos method still insists on routing through arcgis.com

Re: JSON to LayerLegendInfo

ReneRubalcava — Thu, 12 May 2011 17:04:40 GMT

I ran into similar problem at some point, which I thought was weird.
I ended up just parsing the json result, which is fast and gives me a little freedom to do some other stuff with it as well.
https://github.com/odoe/LegendViewer/blob/master/src/net/odoe/flexmaptools/components/helpers/LayerExtractor.as

Re: JSON to LayerLegendInfo

DanielBradshaw — Fri, 13 May 2011 13:48:54 GMT

Thanks for the response Rene. I originally was using the same methods as you (parsing the JSON directly), but the getLegendInfos gives me information about group layers (using the REST enpoint directly doesn't).

That being said... your suggestion inspired me to work up a new strategy for handling group layers within my application using the REST enpoint.

At the end of the day, I still couldn't get the flex API to do what I wanted, but I'm satisfied with my workaround for now.

Re: JSON to LayerLegendInfo

JasonLevine — Fri, 13 May 2011 15:59:34 GMT

That being said... your suggestion inspired me to work up a new strategy for handling group layers within my application using the REST enpoint.

Hi Daniel
Would you mind sharing your new strategy for this? I'm working on the same thing right now.

Thanks,
Jason

Re: JSON to LayerLegendInfo

DanielBradshaw — Fri, 13 May 2011 17:38:35 GMT

No prob...

Disclaimer: This app is a custom app, not built within the flex template.

I have a property in my config file for each layer in my app called legendGroup. This property contains a comma delimited list of layerIds that participate in the "group". For example, say I have a group layer in my MXD with a layerId of 5, and it's children are layers 6, 7, 8. Each of the children have scale dependencies such that only one of them is visible at any given time and I want my legend to reflect only the visible layer. The layer in my config file would have a legendGroup property = "6,7,8".

While building my legend, I pass the legendGroup property and current map scale of the layer of interest to my legend class. I then loop through the JSON results from the legend REST endpoint and find all the layerIds that match one of the layers within my legendGroup. I then loop through the 3 layers that match and compare the legend scale to the map scale I originally passed in. At this point I can confidently pass the "appropriate" legend data back for further processing.

The cons to this solution is you have to manually configure your application to tell it which layers participate in the legend group... but on the flip side you can add as many layers to the group as you want whether they participate in a group layer in the MXD or not, and you always get the legend data for the visible layer in the group.

Make sense?

Re: JSON to LayerLegendInfo

JasonTrimble — Thu, 19 May 2011 18:37:56 GMT

With the help of Tech Support we were able to determine the issue I was having had to do with the timing of when I was calling the getLayerLegendInfo() method.

I was dynamically adding a layer to our map in actionscript and then immediately I would call the getLayerLegendInfo() method to store off the legend data for that layer. The problem is, the layer has not completely loaded at that point. Instead you have to register an event listener for LOAD LayerEvent. When that event fires you can then call the getLayerLegendInfo() method and all the legend data is populated.

The reason the requests attempt to proxy thru arcgis.com is that the underlying legend data retrieval code must look at the version property on the layer. That version property is NaN until the layer has loaded completely, once loaded it is 10.01, which signals to not use the arcgisl.com service for legend data.

Jason

Re: JSON to LayerLegendInfo

AndrewHaigh — Sat, 11 Dec 2021 22:41:20 GMT

Jason,

I can confirm this is correct, I obviously copied an old version of my code onto the forums - sorry everyone!

The correct code snippet is below:

protected function referenceDataLayerLoadComplete(event:FlexEvent):void
{
 // Note that referenceDataMapLayer is an ArcGISDynamicMapServiceLayer from 10.0 SP1
        // we fire the event on the layer LOAD event, otherwise we end up called arcgis.com :(
 var token:AsyncToken = referenceDataMapLayer.getLegendInfos(null);
 var responder:mx.rpc.Responder = new mx.rpc.Responder(getLegendResult, getLegendFault);
 token.addResponder(responder);
}

public function getLegendResult(obj:Object):void
{
 trace("We have a result");
}

public function getLegendFault(obj:Object):void
{
 trace("We have an error");
}

Hope this helps everyone

Andrew