九，query task

FeatureLayer查询的方式：给definitionExpression指定查询条件，

   

   

    Query的字段：text对应的是MapServer的图层的显示字段。

                 returnGeometry：是否返回几何图形，若为false，则不返回图形，只返回属性信息。

                 outFields：是图层对应表里字段的数组。用于指定返回哪些指定的字段。

   

    Query查询主要有三种方式：1，用text和信息进行匹配，（比较简单高效，但是查询功能比较单一）

                             2，给where指定查询的条件，（查询功能比较强，适合用字段进行的查询）

                             3，给geometry指定查询的几个图形范围，（适合根据一个几何图形来查询）

   

    返回结果：1，属性：queryTask.executeLastResult.attributes  属性信息数组

                       queryTask.executeLastResult.features    graphic数组

              2，方法： queryTask.execute(query, new AsyncResponder(onResult, onFault));

                         function onResult(featureSet:FeatureSet, token:Object = null):void

<?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"
               xmlns:esri="http://www.esri.com/2008/ags"
               pageTitle="Query, then zoom to results"
               styleName="plain">

    <s:layout>
        <s:VerticalLayout/>
    </s:layout>

    <fx:Script>
        <![CDATA[
            import com.esri.ags.FeatureSet;
            import com.esri.ags.utils.GraphicUtil;

            import mx.controls.Alert;
            import mx.rpc.AsyncResponder;

            private function doQuery():void
            {
                // clear the graphics layer
                myGraphicsLayer.clear();

                queryTask.execute(query, new AsyncResponder(onResult, onFault));
                function onResult(featureSet:FeatureSet, token:Object = null):void
                {

                    if (featureSet.features.length == 0)
                    {
                        Alert.show("No States found. Please try again.");
                    }
                    else
                    {
                        var graphicsExtent:Extent = GraphicUtil.getGraphicsExtent(featureSet.features);
                        if (graphicsExtent)
                        {
                            map.extent = graphicsExtent;
                        }
                    }
                }
                function onFault(info:Object, token:Object = null):void
                {
                    Alert.show(info.toString());
                }
            }
        ]]>
    </fx:Script>

    <fx:Declarations>
        <!-- Symbol for Query Result as Polygon -->
        <esri:SimpleFillSymbol id="sfs"
                               alpha="0.7"
                               color="0xFF0000"/>

        <!-- Layer with US States -->
        <esri:QueryTask id="queryTask"
                        url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/5"
                        useAMF="false"/>

        <esri:Query id="query"
                    outSpatialReference="{map.spatialReference}"
                    returnGeometry="true"
                    text="{fText.text}">
            <esri:outFields>
                <fx:String>MED_AGE</fx:String>
                <fx:String>POP2007</fx:String>
            </esri:outFields>
        </esri:Query>
    </fx:Declarations>

    <s:BorderContainer width="100%" height="40"
                       backgroundColor="0xDDDDFF"
                       borderVisible="false">
        <s:layout>
            <s:HorizontalLayout horizontalAlign="center"
                                paddingTop="10"
                                verticalAlign="middle"/>
        </s:layout>
        <s:Label text="Search for U.S. States:"/>
        <s:TextInput id="fText"
                     enter="doQuery()"
                     text="Ca"/>
        <s:Button click="doQuery()" label="Query"/>
    </s:BorderContainer>
    <s:Label id="resultSummary" height="15"/>
    <mx:VDividedBox width="100%" height="100%">
        <esri:Map id="map">
            <esri:extent>
                <esri:Extent xmin="-14000000" ymin="2800000" xmax="-7000000" ymax="6400000">
                    <esri:SpatialReference wkid="102100"/>
                </esri:Extent>
            </esri:extent>
            <esri:ArcGISDynamicMapServiceLayer url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Specialty/ESRI_StateCityHighway_USA/MapServer"/>
            <esri:GraphicsLayer id="myGraphicsLayer"
                                graphicProvider="{queryTask.executeLastResult.features}"
                                symbol="{sfs}"/>
        </esri:Map>
        <mx:DataGrid width="100%" height="40%"
                     dataProvider="{queryTask.executeLastResult.attributes}"/>
    </mx:VDividedBox>
</s:Application>