ArcGIS api for javascript——渲染-计算相等间隔分级

描述

本例展示了如何配置分级渲染使用一个相等间隔分类。在这个分类类型中，断点被设置为相等的距离。

可以手工添加相等距离的断点；然而，如果数据被修改了，那些断点就会是不合理的。本例自动地计算断点，因此相同的代码可以用于不同的数据集。

在本例中，断点用相同颜色的逐渐增大的圆符号。如果想要应用某种颜色渐变到断点，需要手工重定义一个颜色数组，然后在循环中给断点加入颜色。

  <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"

    "http://www.w3.org/TR/html4/strict.dtd">

 <html lang="en">

   <head>

     <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

     <meta http-equiv="X-UA-Compatible" content="IE=7" />

     <title>Class Breaks Renderer</title>

     <link rel="stylesheet" type="text/css" href="http://serverapi.arcgisonline.com/jsapi/arcgis/1.5/js/dojo/dijit/themes/tundra/tundra.css">

         <script type="text/javascript">var djConfig = {parseOnLoad: true }</script>

     <script type="text/javascript" src= "http://serverapi.arcgisonline.com/jsapi/arcgis/?v=1.5"></script>

     <script type="text/javascript" charset="utf-8">

       dojo.require("esri.map");

       dojo.require("esri.tasks.query");

       var map;

       var stateName = "Florida";

       var attributeField = "POP1990";

       function init() {

         map = new esri.Map("map", {

           extent: new esri.geometry.Extent({xmin:-88.06640625,ymin:24.45556640625,xmax:-79.27734375,ymax:31.04736328125,spatialReference:{wkid:4326}}),

           slider: false

         });

         dojo.connect(map, "onLoad", doQuery);

         map.addLayer(new esri.layers.ArcGISTiledMapServiceLayer("http://server.arcgisonline.com/ArcGIS/rest/services/ESRI_StreetMap_World_2D/MapServer"));

       }

       //查询所有国家 in Kansas

       function doQuery() {

         var queryTask = new esri.tasks.QueryTask("http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Specialty/ESRI_StatesCitiesRivers_USA/MapServer/0");

         var query = new esri.tasks.Query();

         query.where = "STATE_NAME = '" + stateName + "'";

         query.outFields = [attributeField];

         query.returnGeometry = true;

         queryTask.execute(query, addFeatureSetToMap);

       }

       //添加国家到地图并且应用渲染

       function addFeatureSetToMap(featureSet) {

           var features = featureSet.features;

           var min = max = parseFloat(features[0].attributes[attributeField]);

           //找到Florida 城市中的最少人数和最多人数

           dojo.forEach(features,function(feature) {

               min = Math.min(min,feature.attributes[attributeField]);

               max = Math.max(max,feature.attributes[attributeField]);

           }

           );

           var numRanges = 7;

           var breaks = (max-min) / numRanges;

           var outline = new esri.symbol.SimpleLineSymbol().setWidth(1);//轮廓

           var fillColor = new dojo.Color([240,150,240,0.75]);

           var defaultSymbol = new esri.symbol.SimpleMarkerSymbol().setSize(1).setOutline(outline);

           var renderer = new esri.renderer.ClassBreaksRenderer(defaultSymbol,attributeField);

           for (var i=0;i<numRanges;i++) {

               renderer.addBreak(parseFloat(min + (i*breaks)),

                   parseFloat(min + ((i+1)*breaks)),

                   new esri.symbol.SimpleMarkerSymbol().setSize((i+1)*6).setColor(fillColor).setOutline(outline)); 

           }

           map.graphics.setRenderer(renderer);

           //添加 features 到地图

           dojo.forEach(featureSet.features,function(feature) {

               map.graphics.add(feature);

           });

       }

       dojo.addOnLoad(init);

     </script>

   </head>

   <body>

     <div id="map" class="tundra" style="width:800px; height:400px; border:1px solid #000;"></div>

   </body>

 </html>