topic Re: map.getLayer(id) always retuns null in ArcGIS API for Flex Questions

map.getLayer(id) always retuns null

JesseMetcalfe — Fri, 24 Jun 2011 01:40:06 GMT

Hi,
I want to access a layer from my mapservice so that I can query and apply definition expression to it.
But I am always getting null valye when I access map.getLayer("id") method.

Any help on the right direction is greatly appreciated.

Jesse

Re: map.getLayer(id) always retuns null

NitinBele — Fri, 24 Jun 2011 04:47:03 GMT

In my case I want to access sublayer from a parent layer in the map service.I m too getting null reference when I fire map.getLayer() function.

Any help please ?

Lucas

Re: map.getLayer(id) always retuns null

RobertScheitlin__GISP — Sun, 12 Dec 2021 04:31:51 GMT

Jesse,

Make sure you are passing the getlayer the name of the Map Service as you have it named in the app.

<esri:ArcGISDynamicMapServiceLayer id="Parcels" url="http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/BloomfieldHillsMichigan/Parcels/MapServer"/>
var arc:ArcGISDynamicMapServiceLayer = map.getLayer("Parcels") as ArcGISDynamicMapServiceLayer();

Re: map.getLayer(id) always retuns null

RobertScheitlin__GISP — Fri, 24 Jun 2011 11:04:47 GMT

Lucas,

You can not retrieve a sublayer from the map using this or any function, only a whole Map Service.

Re: map.getLayer(id) always retuns null

NitinBele — Mon, 27 Jun 2011 04:58:13 GMT

Thank you Robert,

Then could you please suggest me the way to perform Definition query on the sublayer of map service ?

I think that only setting <featureLayer>.url (<layerpath>) and <featureLayer>.definitionexpression wont surve the purpose ?

Please suggest.

Lu.

Re: map.getLayer(id) always retuns null

NitinBele — Mon, 27 Jun 2011 05:01:30 GMT

Just to mention that My map service has 4 feature classes (0,1,2,3) and 3 tables (4,5,6).My requirement is to define query on featureclass -1.
I know that var layer:ArcGISDynamicMapServiceLayer = map.getLayer("Parcels") as ArcGISDynamicMapServiceLayer(); will give me reference of Map Service.

Do I have to publish that feature class seperately ?

Lu.

Re: map.getLayer(id) always retuns null

RobertScheitlin__GISP — Mon, 27 Jun 2011 11:04:48 GMT

Lu,

You said

My requirement is to define query on featureclass - 1

Well the QueryTask allows you to specify the exact layer of the map service that you which to query.

Set the URL to the ArcGIS Server REST resource that represents a single layer or table, e.g. http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/5. Note the number "5" at the end of the URL which indicates which specific layer you want to query when querying a map service or a feature service. For an image server, the map service itself is the 'single' layer, so the URL would end with "/MapServer" (without a number).

Now if you only want to visually display a particular layer of a map service on the map than setting the layerDefinitions for the ArcGISDynamicMapServiceLayer is the way to go. A featurelayer is a option but this places all the rendering strain on the client machine and is be overkill for your requirement.

ArcGISDynamicMapServiceLayer info:
http://help.arcgis.com/en/webapi/flex/apiref/com/esri/ags/layers/ArcGISDynamicMapServiceLayer.html

QueryTask Info:
http://help.arcgis.com/en/webapi/flex/apiref/com/esri/ags/tasks/QueryTask.html

Re: map.getLayer(id) always retuns null

NitinBele — Wed, 29 Jun 2011 03:57:30 GMT

Thanks Robert,

That was really helpfull.However I am using FeatureLayer for defining expression and I need to move to layerDefinition.

I did not fully understood the concept of layerDefinitions though.
let say my map service is -
<address>/ArcGIS/rest/services/XYZ/MapServer
It has three Feature Classes -
a - <address>ArcGIS/rest/services/XYZ/MapServer/0
b - <address>ArcGIS/rest/services/XYZ/MapServer/1
c - <address>ArcGIS/rest/services/XYZ/MapServer/2

Now I want to assign LayerDefinition expression (Name = "ABC") to <address>ArcGIS/rest/services/XYZ/MapServer/1
then what should go to my layerDefinitions array ?

     myDynamicLayer.layerDefinitions = [
         null,
         "Name = 'ABC'",
         null,
         ];
Please suggest ?

Lu

Re: map.getLayer(id) always retuns null

RobertScheitlin__GISP — Wed, 29 Jun 2011 11:58:31 GMT

Lu,

The layerDefinitions array is a array that contains a sql statement for every layer in the map service. In your case it would look like:

myDynamicLayer.layerDefinitions = [null, "NAME = 'ABC'", null];

Re: map.getLayer(id) always retuns null

NitinBele — Wed, 06 Jul 2011 05:15:31 GMT

Thanks Robert, it worked like charm.

Lucas.

Re: map.getLayer(id) always retuns null

EzequiasRodrigues_da_Rocha — Mon, 28 Apr 2014 16:06:52 GMT

Lucas,

You can not retrieve a sublayer from the map using this or any function, only a whole Map Service.

Is this real? can't we retrieve the state of any FeatureLayer? Where do we can find this limitation on the documentation Robert?

Ezequias

Re: map.getLayer(id) always retuns null

RobertScheitlin__GISP — Mon, 28 Apr 2014 23:59:39 GMT

Ezequias,

The name "layer" is used by the API in a way that can be confusing. Think of a layer as more of a map service in MOST cases. When working with an ArcGISDynamicMapServiceLayer you are not able to get reference to an individual sublayer of the map service by using map.getLayer function. Using ArcGISDynamicMapServiceLayer you can get access to the sublayers visibility and you can set the layer definition but not a lot more. You can not really call this a limitation that is stated in the documentation, it is more of understanding what abilities the ArcGISDynamicMapServiceLayer actually has by reading the docs.