ext gridpanel 右键菜单怎么动态绑定

grid.on("rowcontextmenu", open_rowcontextmenu);
    function open_rowcontextmenu(grid, rowIndex, e) {
        e.preventDefault();
        var menus = new Ext.menu.Menu
        ([
            {
                text: "删除",
                pressed: true,
                handler: a

            },
            {
                text: "添加到节目列表",
                pressed: true,
                handler: a
            }
        ]);
        menus.showAt(e.getPoint());
    }
    function a() {
        alert("ok");
    }