如何修改树图标

<data-dojo-args="item,opened">if(item && continentStore.getValue(item,"type") == "continent"){return {backgroundImage: "url('../images/flatScreen.gif')",height: "32px",width: "32px"};}else{return null;}</script>//var param = dijit.byId('flowForm').get('value');//param.startDate =  dojo.date.stamp.toISOString(param.startDate, {selector: 'date'});//param.endDate = dojo.date.stamp.toISOString(param.endDate , {selector: 'date'});