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FeatureLayer from JSON

RoryHanlon

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

json-example.zip

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Accepted answers

derekswingley1

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.

All comments

AdamJoseph1

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

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

khutchins

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>

derekswingley1

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