请教一个Ext问题

Question

//左侧布局var url = "Operate.aspx?opt=tree";
var loader = new Ext.tree.TreeLoader({
    url:url,
    requestMethod: 'GET',
    listeners:{
        "loadexception":function(loader,node,response){
            //加载服务器数据,直到成功
            node.loaded = false;
            node.reload.defer(10,node);
         }
    }
});//根节点
var root = new Ext.tree.AsyncTreeNode({
     id:"0", 
     text:"系统管理",
     leaf:false,
     loader:loader,
     expandable:true,
     expanded:true //展开,默认不展开
}); //tree面板
var treePanel = new Ext.tree.TreePanel({
     id:"tree",
     root:root,   //加载根节点 
     singleExpand:true,
     autoHeight:true,
     autoWidth:true,
     frame:false,
     lines:true,//节点之间连接的横竖线         
     animate:true   //以动画形式伸展,收缩子节点
     
});