类似于文件夹的展开和折叠

if ($(img).attr("src").indexOf("minus.gif") > -1)
   {
       isNeedCollapse=true;
       $(img).attr("src","/omsys2/html/style/default/images/plus.gif");
   }
   else if ($(img).attr("src").indexOf("plus.gif") > -1)
   {
       isNeedCollapse = false;    
       $(img).attr("src","/omsys2/html/style/default/images/minus.gif");
   }