extjs的formpanel定制右键菜单

var form=new Ext.form.FormPanel({
         labelAlign:'right',
        id:'topFormId',
       labelWidth:60,
        title:'基本信息',
        frame:true,
        width:lh.screenAvailWidth,
        items:[{
            layout:'column',
            items:[{
                columnWidth:0.04,
                layout:'form',
                items:[{xtype:'box',autoEl:{//显示从莞的图片
                    tag:'div',
                    children:[{
                        tag:'img',
                        qtip:'从莞高速公路投资有限公司图标',
                        src:'images/congGuan.jpg',
                        height:50,
                        width:50
                    }]
                }}
                ]
            },{
                 columnWidth:0.20,
                 layout:'form',
                items:[{xtype:'box',id:'testId',html:'<h1 style="font-size:15pt">从莞高速公路惠州段<br/>项目建设管理平台(PMP)</h1>',boxMinWidth:150}]
            },{
                columnWidth:0.76,
                layout:'form',
                id:'topmenu',
                items:[tb]
            }]
        }],
        listeners:{
            render:function(p){
                p.getEl().on("click",function(e){//单击事件
                   alert('onclick');
                });
                p.getEl().on("contextmenu",function(e){//右键事件
                       e.preventDefault();
                       contextmenu.showAt(e.getXY());
                })
            }
        }
    });