Jenna,
Not exactly what you asked for but another way to do it:
If you really need it to use a QueryTask then let me know and I will change the sample to use QueryTask
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<!--The viewport meta tag is used to improve the presentation and behavior of the samples
on iOS devices-->
<meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no">
<title>Buffer</title>
<link rel="stylesheet" href="http://js.arcgis.com/3.11/dijit/themes/tundra/tundra.css">
<link rel="stylesheet" href="http://js.arcgis.com/3.11/esri/css/esri.css">
<style>
html,
body,
#mapDiv {
padding: 0;
margin: 0;
height: 100%;
}
#messages {
background-color: #fff;
box-shadow: 0 0 5px #888;
font-size: 1.1em;
max-width: 15em;
padding: 0.5em;
position: absolute;
right: 20px;
top: 20px;
z-index: 40;
}
#drop {
background-color: #fff;
box-shadow: 0 0 5px #888;
font-size: 1.1em;
max-width: 15em;
padding: 0.5em;
position: absolute;
right: 20px;
top: 105px;
z-index: 40;
}
</style>
<script src="http://js.arcgis.com/3.11/"></script>
<script>
var map;
require([
"esri/map", "esri/layers/FeatureLayer",
"esri/tasks/query", "esri/geometry/Circle", "esri/units",
"esri/graphic", "esri/InfoTemplate", "esri/symbols/SimpleMarkerSymbol",
"esri/symbols/SimpleLineSymbol", "esri/symbols/SimpleFillSymbol", "esri/renderers/SimpleRenderer",
"esri/config", "esri/Color", "dojo/dom", "dijit/form/ComboBox", "dojo/domReady!"
], function (
Map, FeatureLayer,
Query, Circle, Units,
Graphic, InfoTemplate, SimpleMarkerSymbol,
SimpleLineSymbol, SimpleFillSymbol, SimpleRenderer,
esriConfig, Color, dom
) {
// use a proxy page if a URL generated by this page is greater than 2000 characters
//
// this should not be needed as nearly all query & select functions are performed on the client
esriConfig.defaults.io.proxyUrl = "/proxy/";
map = new Map("mapDiv", {
basemap: "streets",
center: [-81.00, 34.000],
zoom: 14,
slider: false
});
//add the census block points in on demand mode. Note that an info template has been defined so when
//selected features are clicked a popup window will appear displaying the content defined in the info template.
var featureLayer = new FeatureLayer("http://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/0", {
outFields: ["POP2000", "HOUSEHOLDS", "HSE_UNITS", "TRACT", "BLOCK"]
});
// selection symbol used to draw the selected census block points within the buffer polygon
var symbol = new SimpleMarkerSymbol(
SimpleMarkerSymbol.STYLE_CIRCLE,
6,
new SimpleLineSymbol(
SimpleLineSymbol.STYLE_NULL, new Color([200, 120, 101, 0.9]), 1),
new Color([200, 0, 0, 1])
);
featureLayer.setSelectionSymbol(symbol);
//make unselected features invisible
var nullSymbol = new SimpleMarkerSymbol().setSize(0);
featureLayer.setRenderer(new SimpleRenderer(nullSymbol));
map.addLayer(featureLayer);
var circleSymb = new SimpleFillSymbol(
SimpleFillSymbol.STYLE_NULL,
new SimpleLineSymbol(
SimpleLineSymbol.STYLE_SHORTDASHDOTDOT,
new Color([105, 105, 105]),
2
), new Color([255, 255, 0, 0.25])
);
var circle;
//when the map is clicked create a buffer around the click point of the specified distance.
map.on("click", function (evt) {
selbuf = document.FormSelection.BufferSelection.selectedIndex;
var BufferSelection = document.FormSelection.BufferSelection.options[selbuf].value;
circle = new Circle({
center: evt.mapPoint,
geodesic: true,
radius: BufferSelection,
radiusUnit: Units.MILES
});
map.graphics.clear();
map.infoWindow.hide();
var graphic = new Graphic(circle, circleSymb);
map.graphics.add(graphic);
var query = new Query();
query.geometry = circle;
featureLayer.selectFeatures(query, FeatureLayer.SELECTION_NEW, function (results) {
var totalPopulation = sumPopulation(results);
var r = "";
r = "<b>The total Census Block population within the buffer is <i>" + totalPopulation + "</i>.</b>";
dom.byId("messages").innerHTML = r;
});
});
function sumPopulation(features) {
var popTotal = 0;
for (var x = 0; x < features.length; x++) {
popTotal = popTotal + features.attributes["POP2000"];
}
return popTotal;
}
});
</script>
</head>
<body>
<span id="messages">Click on the map to select census block points within mile.</span>
<span id="drop">
<form name="FormSelection">
<select name="BufferSelection">
<option>1</option>
<option>2</option>
<option>10</option>
</select>
</form>
</span>
<div id="mapDiv"></div>
</body>
</html>