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View Geometry Service - Points for labeling sample in sandbox
Geometry Service - Points for labeling

Description

As an alternative to the label layer, you can create a label for one or more individual features by placing a text symbol at a given point. To do this, use the geometry service to generate a point for placing a label inside a polygon.

To try this sample, draw a polygon on the map. When you submit the polygon, it's simplified so it won't throw errors if it overlaps itself. The GeometryService.labelPoints() method determines a point inside the polygon. The parameters are an array of polygon graphics to be labeled and a callback function specifying what to do with the label points. In most cases, you'll be associating each point with a TextSymbol, like this:

labelPoints[i].setSymbol(textSymbol);

Code

<!DOCTYPE html>
<html>
 
<head>
   
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
   
   
<meta name="viewport" content="initial-scale=1, maximum-scale=1, user-scalable=no">
   
<title>Geometry Service: Label Points</title>

   
<link rel="stylesheet" href="https://js.arcgis.com/3.46/dijit/themes/nihilo/nihilo.css">
   
<link rel="stylesheet" href="https://js.arcgis.com/3.46/esri/css/esri.css">
   
<style>
      html
, body, #mapDiv {
        height
: 100%;
        margin
: 0;
        padding
: 0;
        width
: 100%;
     
}
     
#info {
        bottom
: 20px;
        color
: #444;
        height
: auto;
        font
-family: arial;
        left
: 20px;
        margin
: 5px;
        padding
: 10px;
        position
: absolute;
        width
: 200px;
        z
-index: 40;
     
}
   
</style>

   
<script src="https://js.arcgis.com/3.46/"></script>
   
<script>
      require
(["dojo/dom",
     
"dojo/dom-attr",
     
"dojo/_base/array",
     
"esri/Color",
     
"dojo/number",
     
"dojo/parser",
     
"dijit/registry",

     
"esri/config",
     
"esri/map",
     
"esri/graphic",
     
"esri/tasks/GeometryService",
     
"esri/tasks/BufferParameters",
     
"esri/toolbars/draw",
     
"esri/symbols/SimpleMarkerSymbol",
     
"esri/symbols/SimpleLineSymbol",
     
"esri/symbols/SimpleFillSymbol",
     
"esri/symbols/Font",
     
"esri/symbols/TextSymbol",

     
"dijit/layout/BorderContainer",
     
"dijit/layout/ContentPane"
 
], function(dom, domAttr, array, Color, number, parser, registry, esriConfig, Map, Graphic, GeometryService, BufferParameters, Draw,
             
SimpleMarkerSymbol, SimpleLineSymbol, SimpleFillSymbol, Font, TextSymbol) {

   
var map, toolbar, geometryService;

    parser
.parse();

   
// create the map control
    map
= new Map("mapDiv", {
      basemap
: "streets-vector",
      center
: [-117.215, 34.05],
      zoom
: 13,
      showAttribution
: false
   
});

   
// create a toolbar for the map
    toolbar
= new Draw(map);
    toolbar
.on("draw-end", addToMap);

   
// activate a drawing tool when a button is clicked
    registry
.byId("polygon").on("click", function() {
      toolbar
.activate(Draw.POLYGON);
      map
.hideZoomSlider();
   
});
    registry
.byId("freehand").on("click", function() {
      toolbar
.activate(Draw.FREEHAND_POLYGON);
      map
.hideZoomSlider();
   
});
    registry
.byId("clear").on("click", function() {
      map
.graphics.clear();
   
});

    geometryService
= new GeometryService("https://utility.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer");

   
function addToMap(evtObj) {
      map
.graphics.clear();
     
var geometry = evtObj.geometry;
     
// add the drawn graphic to the map
     
var symbol = new SimpleFillSymbol(
       
SimpleFillSymbol.STYLE_SOLID,
       
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID, new Color([0, 0, 0]), 2),
       
new Color([0, 0, 255, 0.5]));
     
var graphic = new Graphic(geometry, symbol);
      map
.graphics.add(graphic);

     
// simplify polygon so it can be used in the get label points request
      geometryService
.simplify([geometry], getLabelPoints);
   
}

   
function getLabelPoints(geometries) {
     
if (geometries[0].rings.length > 0) {
        geometryService
.labelPoints(geometries, function(labelPoints) { // callback
          toolbar
.deactivate();
          map
.showZoomSlider();

         
var font = new Font("20px", Font.STYLE_NORMAL, Font.VARIANT_NORMAL, Font.WEIGHT_BOLDER);
          array
.forEach(labelPoints, function(labelPoint) {
           
// create a text symbol
           
var textSymbol = new TextSymbol(
             
"X: " + number.format(labelPoint.x) + ", Y: " + number.format(labelPoint.y),
              font
, new Color([0, 0, 0]));

           
var labelPointGraphic = new Graphic(labelPoint, textSymbol);

           
// add the label point graphic to the map
            map
.graphics.add(labelPointGraphic);
         
});
       
});
     
} else {
        alert
("Invalid Polygon - must have at least 3 points");
     
}
   
}
 
});
 
</script>

 
</head>

 
<body class="nihilo">
   
<div id="mapDiv"></div>
   
<div id="info" class="esriSimpleSlider">
     
<button id="polygon" data-dojo-type="dijit.form.Button">Polygon</button>
     
<button id="freehand" data-dojo-type="dijit.form.Button">Freehand Polygon</button>
     
<button id="clear" data-dojo-type="dijit.form.Button">Clear Graphics</button>
   
</div>
 
</body>

</html>
 
         
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