identifyTask练习

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
			   xmlns:s="library://ns.adobe.com/flex/spark" 
			   xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600" xmlns:esri="http://www.esri.com/2008/ags">
	<fx:Script>
		<![CDATA[
			import com.esri.ags.Graphic;
			import com.esri.ags.events.MapMouseEvent;
			import com.esri.ags.geometry.Geometry;
			import com.esri.ags.symbols.InfoSymbol;
			import com.esri.ags.tasks.supportClasses.IdentifyParameters;
			import com.esri.ags.tasks.supportClasses.IdentifyResult;
			
			import mx.controls.Alert;
			import mx.rpc.AsyncResponder;
			[Bindable]private var lastIdentifyResultGraphic:Graphic;
             private function mapClickHandler(event:MapMouseEvent):void
			 {
				 clickGraphicsLayer.clear();
				 
				 var identifyParams:IdentifyParameters = new IdentifyParameters();
				 identifyParams.returnGeometry = true;
				 identifyParams.tolerance = 3;
				 identifyParams.width = myMap.width;
				 identifyParams.height = myMap.height;
				 identifyParams.geometry = event.mapPoint;
				 identifyParams.mapExtent = myMap.extent;
				 identifyParams.spatialReference = myMap.spatialReference;
                    var clickGraphic:Graphic=new Graphic(event.mapPoint,SMS);
				    clickGraphicsLayer.add(clickGraphic);
					identifyTask.execute(identifyParams, new AsyncResponder(myResultFunction, myFaultFunction, clickGraphic));
			 }
			private function myResultFunction(results:Array,clickGraphic:Graphic=null):void
			{
				if(results&&results.length>0)
				{
					var result:IdentifyResult=results[0];
					var resultGraphic:Graphic=result.feature;
					switch (resultGraphic.geometry.type)
					{
						case Geometry.MAPPOINT:
						{
							resultGraphic.symbol = SMS;
							break;
						}
						case Geometry.POLYLINE:
						{
							resultGraphic.symbol = SLS;
							break;
						}
						case Geometry.POLYGON:
						{
							resultGraphic.symbol = SFS;
							break;
						}
					}
				  lastIdentifyResultGraphic=resultGraphic;
                  clickGraphic.symbol=new InfoSymbol();
				  clickGraphic.attributes=resultGraphic.attributes;
				}
			}
			private function myFaultFunction(error:Object, clickGraphic:Graphic = null):void
			{
				Alert.show(String(error), "Identify Error");
			}

		]]>
	</fx:Script>
	<fx:Declarations>
		<!-- 将非可视元素（例如服务、值对象）放在此处 -->
		<esri:SimpleMarkerSymbol id="SMS" color="0xFF0000" size="12" style="circle"/>
		<esri:SimpleLineSymbol id="SLS" color="0xFF0000" width="2" alpha="1" style="solid"/>
		<esri:SimpleFillSymbol id="SFS" color="0xFF0000"/>
		<esri:IdentifyTask id="identifyTask" concurrency="last"
						   url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Specialty/ESRI_StatesCitiesRivers_USA/MapServer"/>
	</fx:Declarations>
	<esri:Map id="myMap"
			  mapClick="mapClickHandler(event)"
			  openHandCursorVisible="false">
		<esri:extent>
			<esri:WebMercatorExtent minlon="-120" minlat="30" maxlon="-100" maxlat="50"/>
		</esri:extent>
		<esri:ArcGISTiledMapServiceLayer url="http://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer"/>
		<esri:GraphicsLayer graphicProvider="{lastIdentifyResultGraphic}"/>
		<esri:GraphicsLayer id="clickGraphicsLayer"/>
	</esri:Map>

</s:Application>

该练习涉及到的知识点：

1 先定义了一个Identify Task对象，如下面代码：

 

<esri:IdentifyTask id="identifyTask"
       identifyComplete="identifyCompleteHandler(event)"
url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Specialty/ESRI_States
CitiesRivers_USA/MapServer"/>

   其中，identifyComplete事件绑定IdentifyCompleteHandler(event)函数，即IdentifyTask对象设置完成之后实现该函数，url指定IdentifyTask服务地址。但在练习中没有用到该绑定事件。

2 执行Identify，需要定义一个IdentifyParameters对象，把所需要的参数进行传递，其中tolerance是容差半径，geometry是用来做Identify的几何对象。此外还定义了clickGraphic用来设置鼠标点击出现的符号

    identifyTask.execute(identifyParams, new AsyncResponder(myResultFunction, myFaultFunction, clickGraphic));

这句代码主要用来向REST请求Identify服务，并设置了请求服务成功则调用myResultFunction函数,失败则调用myFaultFunction函数(这就是前面定义IdentifyTask时不设置identifyComplete事件的原因）

3 接下来主要是编写myResultFunction函数

  var result:IdentifyResult=results[0];var resultGraphic:Graphic=result.feature;

用IdentifyResult来获取feature并赋予resultGraphic对象，并根据该对象的几何性质赋予渲染符号；最后把resultGraphic的属性赋给clickGraphic并用InfoSymbol显示出来另外需要注意的是：<esri:GraphicsLayer graphicProvider="{lastIdentifyResultGraphic}"/>lastIdentifyResultGraphic=resultGraphic;实验设置了一个全局变量作为GraphicLayer的数据源。