IMSMap.zoomToSelection

<P>IMSMap.zoomToSelection ，在java viewer下，如何把选到的道路高亮显示，或描红。 </P><PRE>//SETS THE SYMBOL AND COLOR TO SELECT THE FEATURE<br>var selSymbol =parent.mapFrame.IMSMap.createSymbol("POLYGON_SYMBOL");<br><br>var selColor = parent.mapFrame.IMSMap.createColor(0,0,255);<br><br>selSymbol.setBoundaryColor(selColor);<br>selSymbol.setFillTransparency(0);<br><br><br>//Select the Layer to be active<br>     parent.mapFrame.IMSMap.setSelectedLayer("County");<br><br>//Assign the selected symbol to the layer<br>layer.setSelectionSymbol(selSymbol);<br><br>var queryString = "COUNTY = "+ Value1;<br>     parent.mapFrame.IMSMap.zoomToSelection("County", queryString);<br><br>layer.select(queryString);<br></PRE>
<P>见有这么写的，请问，var selSymbol =parent.mapFrame.IMSMap.createSymbol("POLYGON_SYMBOL"); 这句是干什么用的，POLYGON_SYMBOL是什么？</P>
<P>我这么写，怎么不能用？</P>
<P>谢谢</P>