arcgis api for flex 开发入门（六）identify

identify 是GIS中比较常用的工具之一，在arcgis api for flex中esri为我们提

供了一个Identify Task来轻松完成identify 的功能。

首先，还是使用<esri:IdentifyTask>标签来创建一个Identify Task。

<!-- Identify Task -->

<esri:IdentifyTask id="identifyTask"

identifyComplete="identifyCompleteHandler(event)"

url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Special

ty/ESRI_StatesCitiesRivers_USA/MapServer"/>

当identifyTask执行完毕的时候响应identifyComplete消息，我们就可以把

identify的结果做一些处理，比如添加到Graphic layer 上。

在执行identify之前，首先要对identify的参数设置一下，我们需要一个

IdentifyParameters对象。下面的代码是AS3脚本的代码，用来创建

IdentifyParameters和identify执行。

var identifyParams : IdentifyParameters = new IdentifyParameters();

identifyParams.returnGeometry = true;

identifyParams.tolerance = 3;

identifyParams.width = 600;

identifyParams.height = 550;

identifyParams.geometry = geometry;

identifyParams.layerOption =

IdentifyParameters.LAYER_OPTION_ALL;

identifyParams.mapExtent = map.extent;

identifyTask.execute( identifyParams );

其中tolerance是容差半径

width:Width of the map currently being viewed in pixels.

height : Height of the map currently being viewed in pixels

geometry 是用来做identify的几何，常用的有点选，矩形选择，多边形选择等

参数设置好了之后，直接调用identifyTask.execute( identifyParams );就ok了

。

那么我们用来做identify的几何怎么来呢，在什么时候去做Identify呢？

首先回答第一个问题，做identify的几何我们可以利用第四讲中draw控件使用鼠

标交互来获得，这也是RIA的特点之一。

那么在什么时候做identify呢？

就在做identify的几何画完之后做，嘿嘿，等于没说嘛，当然要在画完了就做:-D

现在我们就来完成上面的工作

定义一个draw控件

<esri

raw
id="drawToolbar" map="{map}"

graphicsLayer="{myGraphicsLayer}" drawEnd="drawEndHandler(event)">

记得添加上drawEnd消息的响应函数drawEndHandler(event)，这个事件会在draw

之后响应。

用as3脚本实现drawEndHandler和identifyCompleteHandler函数

private function drawEndHandler(event

rawEvent):void

{

var geometry : Geometry = event.geometry;

var identifyParams : IdentifyParameters = new

IdentifyParameters();

identifyParams.returnGeometry = true;

identifyParams.tolerance = 3;

identifyParams.width = 600;

identifyParams.height = 550;

identifyParams.geometry = geometry;

identifyParams.layerOption =

IdentifyParameters.LAYER_OPTION_ALL;

identifyParams.mapExtent = map.extent;

identifyTask.execute( identifyParams );

private function identifyCompleteHandler

(event:IdentifyEvent):void

{

for each (var result:IdentifyResult in

event.identifyResults)

{

myGraphicsLayer.add(result.feature);

}

}

<?xml version="1.0" encoding="utf-8"?>
<mx:Application
xmlns:mx="http://www.adobe.com/2006/mxml"
xmlns:esri="http://www.esri.com/2008/ags"
layout="absolute"
pageTitle="Identify Features on the Map"
>
<mx:Script>
<![CDATA[
import com.esri.ags.Graphic;
import com.esri.ags.events.DrawEvent;
import com.esri.ags.events.IdentifyEvent;
import com.esri.ags.geometry.Geometry;
import com.esri.ags.symbol.Symbol;
import com.esri.ags.tasks.IdentifyParameters;
import com.esri.ags.tasks.IdentifyResult;
import com.esri.ags.toolbars.Draw;
private function drawEndHandler(event:DrawEvent):void
{
var geometry : Geometry = event.geometry;
var identifyParams : IdentifyParameters = new
IdentifyParameters();
identifyParams.returnGeometry = true;
identifyParams.tolerance = 3;
identifyParams.width = 600;
identifyParams.height = 550;
identifyParams.geometry = geometry;
identifyParams.layerOption =
IdentifyParameters.LAYER_OPTION_ALL;
identifyParams.mapExtent = map.extent;

identifyTask.execute( identifyParams );
}

private function identifyCompleteHandler
(event:IdentifyEvent):void
{
for each (var result:IdentifyResult in
event.identifyResults)
{
myGraphicsLayer.add(result.feature);
}
}
]]>
</mx:Script>
<!-- Draw ToolBar -->
<esri:Draw id="drawToolbar" map="{map}"
graphicsLayer="{myGraphicsLayer}" drawEnd="drawEndHandler(event)">
</esri:Draw>
<!-- Identify Task -->
<esri:IdentifyTask id="identifyTask"
identifyComplete="identifyCompleteHandler(event)"

url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Special
ty/ESRI_StatesCitiesRivers_USA/MapServer"/>
<mx:Panel  width="100%" height="100%">
<mx:Button label="Identify" click="drawToolbar.activate
(Draw.MAPPOINT)"/>
<esri:Map id="map" width="100%" height="100%">
<esri:ArcGISDynamicMapServiceLayer

url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Special
ty/ESRI_StatesCitiesRivers_USA/MapServer" />
<esri:GraphicsLayer id="myGraphicsLayer"/>
</esri:Map>
</mx:Panel>
</mx:Application>