topic Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer in .NET Maps SDK Questions

Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

xiaoguangyan — Tue, 25 Jul 2017 01:29:04 GMT

Hi, I Define LabelDefinition for ArcGISMapImageSublayer after the ArcGISMapImagelayer loaded, but the labels don't show, the field is to be labeld is "name"

private async void ArcGISMapImageLayer_LoadStatusChanged(object sender, LoadStatusEventArgs e)
{
var lyr = sender as ArcGISMapImageLayer;

if (e.Status == LoadStatus.Loaded)
{
var subLyr = lyr.Sublayers[1] as ArcGISMapImageSublayer;
await subLyr.LoadAsync();
subLyr.LabelDefinitions.Add(LabelDefinition.FromJson("{\"labelExpression\": \"[name]\",\"labelPlacement\": \"esriServerPolygonPlacementAlwaysHorizontal\",\"symbol\": {\"color\": [255,0,255,123],\"font\": {\"size\": 16},\"type\": \"esriTS\"}}"));
}
}

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

NagmaYasmin — Tue, 25 Jul 2017 04:14:24 GMT

Hi Yan,

Since you are using ArcGISMapImageLayer, you need to define the label expression in json format. Please see the documentation link :

"Labels for map image sublayers (ArcGISMapImageLayer) can be defined in much the same way as labels for feature layers and graphics overlays. The main difference is that labels for map image layers are rendered by the server and not in your client app. You must therefore use ArcGIS Server REST API syntax to define your label expressions, rather than the Arcade syntax you can use with feature layers and graphics overlays."

Label map features—ArcGIS Runtime SDK for .NET (WPF) | ArcGIS for Developers

Hope that helps

Nagma

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

xiaoguangyan — Tue, 25 Jul 2017 06:16:03 GMT

Hi Nagma

I have noticed that the difference between map image layers and feature layer, I use the ArcGIS Server REST API syntax to define my Json, but labels still don't show

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

JenniferNery — Sun, 12 Dec 2021 05:11:06 GMT

I tried your label JSON and it seems valid. Does 'name' attribute exist on the service? You also might be missing LabelsEnabled=true.

I updated the JSON a bit to fit the service in this sample.

            MyMapView.Map = new Map(Basemap.CreateTopographic());
            var layer = new ArcGISMapImageLayer(new Uri("http://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer"));
            layer.Loaded += (s, e) =>
              {
                  var subLayer = (ArcGISMapImageSublayer)layer.Sublayers[2];
                  subLayer.LabelsEnabled = true;
                  subLayer.LabelDefinitions.Add(LabelDefinition.FromJson(("{\"labelExpression\": \"[state_name]\",\"labelPlacement\": \"esriServerPolygonPlacementAlwaysHorizontal\",\"symbol\": {\"color\": [255,0,255,123],\"font\": {\"size\": 16},\"type\": \"esriTS\"}}")));
              };
            MyMapView.Map.OperationalLayers.Add(layer);‍‍‍‍‍‍‍‍‍

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

xiaoguangyan — Wed, 26 Jul 2017 01:39:23 GMT

Hi Jennifer

I have set LabelsEnabled=true, but I noticed that the service you test http://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer/2 the "Can Modify Layer: true" , but mine is false, and I try another service with Can Modify Layer: false, the labels will don't show all the same. So I doubt that if the Can Modify Layer: true is necessary for LabelDefination of ArcGISMapImageSubLayer?

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

MichaelBranscomb — Wed, 26 Jul 2017 20:14:25 GMT

Hi,

Yes, that's correct - your service must allow per layer modification, exposed in the capabilities as "Can Modify Layer" / "canModifyLayer".

The modification of ArcGISMapImageSublayers uses the DynamicLayer capability of the MapServer endpoint - for more info see ArcGIS REST API

Cheers

Mike

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

xiaoguangyan — Fri, 28 Jul 2017 10:38:49 GMT

I use the ArcGISmapimagelayer with Can Modify Layer=True , but the labels show in messy code like pic below

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

NagmaYasmin — Fri, 28 Jul 2017 16:03:29 GMT

Hi Yan,

I believe you are trying to display the labels in Chinese characters. If that is the case, labels displayed in Chinese language isn't supported yet, that's my understanding.

Best,

Nagma

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

xiaoguangyan — Sat, 29 Jul 2017 04:32:18 GMT

Hi, Nagma

I do want to display the labels in Chinese characters, I am sorry to hear that labels displayed in Chinese language isn't supported yet.

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

HTKSHI — Tue, 08 Aug 2017 02:44:50 GMT

font tag set font_family which support Chinese characters

e.g：

"{\"labelExpression\": \"[state_name]\",\"labelPlacement\": \"esriServerPolygonPlacementAlwaysHorizontal\",\"symbol\": {\"color\": [255,0,255,123],\"font\": {\"size\": 16,\"family\":\"Microsoft YaHei\"},\"type\": \"esriTS\"}}"

Re: Label don't show After Define LabelDefinition for ArcGISMapImageSublayer

xiaoguangyan — Tue, 08 Aug 2017 03:28:03 GMT

Thanks, That helps much