FeatureLayer from JSON

RoryHanlon — Tue, 31 Jan 2012 08:45:03 GMT

Hi,

I'm trying to create a simple piece of code that uses a JSON string to create a FeatureLayer. I'd got to the point where it was adding 1 point out of the 4 specified, in the JSON, to the map. To cut a long story short, I eventually found this thread below to be able to compare against a working example

http://forums.arcgis.com/threads/18859-Creating-a-FeatureLayer-from-a-FeatureCollection.-Base64-in-Internet-Explorer?highlight=FeatureLayer+json

The fundamental difference appeared to be that I was using API 2.6 and this example used 2.1 as the exact same code works fine after changing the api reference. Could anyone give me a pointer as to how I'm supposed to get all my points appearing in the FeatureLayer with the 2.6 API? I can't find any indications as to what would have changed, from the reference material. I've attached a zip with my simple example. The featureset imports the json correctly but loses all but one of the points when added.

Thanks

Re: FeatureLayer from JSON

derekswingley1 — Tue, 31 Jan 2012 16:16:08 GMT

Your feature layer needs an object id field, check out this discussion on gis.stackexchange.com: http://gis.stackexchange.com/a/8912/124

It's also worth look at the feature layer from a feature collection sample.

Re: FeatureLayer from JSON

KellyHutchins — Sat, 11 Dec 2021 11:05:17 GMT

Derek is correct you need the object id. Here's an example:

<html>
  
  <head>
    <link rel="stylesheet" type="text/css" href="http://serverapi.arcgisonline.com/jsapi/arcgis/2.6/js/dojo/dijit/themes/claro/claro.css">
    <script src="http://serverapi.arcgisonline.com/jsapi/arcgis/?v=2.6" type="text/javascript"></script>
    <script type="text/javascript">
      dojo.require("esri.map");
      dojo.require("esri.layers.FeatureLayer");
      var map = null;
      var featureLayer = null;

      function init() {

        map = new esri.Map("map", {
          extent: new esri.geometry.Extent({
            xmin: -1040766.5771306533,
            ymin: 7095190.713541364,
            xmax: -766204.7715304322,
            ymax: 7278028.085199418,
            spatialReference: {
              wkid: 102100
            }
          })
        });

        // for webmaps
        var arcgisURL = "http://server.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer"
        // 102100 
        var tiledMapServiceLayer = new esri.layers.ArcGISTiledMapServiceLayer(arcgisURL);
        map.addLayer(tiledMapServiceLayer);


      }



      function createFeatureLayer() {
        var jsonFS = {
          "geometryType": "esriGeometryPoint",
          "features": [
      {
            "attributes": {
              "Name": "Point1",
              "ObjectID": 1
            },
            "geometry": {
              "x": -958520.3346958433,
              "y": 7120873.555045171
            }
          },
      {
            "attributes": {
              "Name": "Point2",
              "ObjectID": 2
            },
            "geometry": {
              "x": -803811.7894467209,
              "y": 7122708.0437240143

            }
          },
      {
            "attributes": {
              "Name": "Point3",
              "ObjectID": 3
            },
            "geometry": {
              "x": -782409.4215268819,
              "y": 7208317.51540337

            }
          },
      {
            "attributes": {
              "Name": "Point4",
              "ObjectID": 4
            },
            "geometry": {
              "x": -1017529.720531971,
              "y": 7189666.8805017965

            }
          }
    ]
        };
        var fs = new esri.tasks.FeatureSet(jsonFS);
        var fsCollect = new esri.tasks.FeatureSet();
        var featuresList = fs.features;

        var layerDefinition = {
          "displayFieldName": "Name",
          "geometryType": "esriGeometryPoint",
          "spatialReference": {
            "wkid": 102100
          },
          "fields": [{
            "name": "ObjectID",
            "alias": "ObjectID",
            "type": "esriFieldTypeOID"
          }, {
            "name": "Name",
            "type": "esriFieldTypeString",
            "alias": "Name"
          }]
        }

        var featureCollection = {
          layerDefinition: layerDefinition,
          featureSet: fs
        };


        //alert(featureCollection.featureSet.features.length);
        console.log(featureCollection);
        featureLayer = new esri.layers.FeatureLayer(featureCollection);
        var defaultSymbol = new esri.symbol.SimpleMarkerSymbol();


        var renderer = new esri.renderer.UniqueValueRenderer(defaultSymbol, "Name");

        //add symbol for each possible value
        renderer.addValue("Point1", new esri.symbol.SimpleMarkerSymbol().setColor(new dojo.Color([255, 0, 0, 0.5])));
        renderer.addValue("Point2", new esri.symbol.SimpleMarkerSymbol().setColor(new dojo.Color([0, 255, 0, 0.5])));
        renderer.addValue("Point3", new esri.symbol.SimpleMarkerSymbol().setColor(new dojo.Color([0, 0, 255, 0.5])));
        renderer.addValue("Point4", new esri.symbol.SimpleMarkerSymbol().setColor(new dojo.Color([255, 0, 255, 0.5])));
        featureLayer.setRenderer(renderer);


        map.addLayer(featureLayer);
        dojo.connect(map, 'onClick', function (e) {
          console.log(e.mapPoint.x + " " + e.mapPoint.y);
        });

      }

      function checkNoRecords() {
        if (featureLayer != null) {
          alert("Number of records " + featureLayer.graphics.length);
        } else alert("Feature Layer is null");
      }

      function getExtent() {

        document.write("MinX: " + map.extent.xmin + " MinY: " + map.extent.ymin + " MaxX: " + map.extent.xmax + " MaxY: " + map.extent.ymax);

      }

      dojo.addOnLoad(init);
    </script>
  </head>
  
  <body class='claro'>
    <div id="map" style="width:900px; height:600px; border:1px solid #000;"></div>
    <button onclick="createFeatureLayer()">Create Feature Layer</button>
    <button onclick="checkNoRecords()">Check number of records in featurelayer</button>
  </body>

</html>

Re: FeatureLayer from JSON

AdamJoseph1 — Wed, 08 Jul 2015 23:32:07 GMT

alternative load your JSON to PostGIS database then use Cartoview to serve it out.

Cartoview will install on windows, with Python and PostGIS included.

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