ExtJS 按钮重新渲染的有关问题

ExtJS 按钮重新渲染的问题
本人想通过事件触发来重新渲染button 空间的背景 但是没有效果啊~！ 求助高人帮忙。API里面也没有相应重新渲染的方法啊~！

代码如下：

JScript code

var imageBtn = Ext.create("Ext.button.Button", {                y: 2,                width: everyBtnWidth,                height: everyBtnHeight,                element: _skinModulePosition,                style: 'background:url(' + loadIcon + ')',                listeners: {                    "click": function (element) {                        me.skipFunction(workarea, element);                    },                    "mouseover": function (element) {                        //var tempModelName = Ext.getCmp();                        var mouseoverImg = "./images/homepage/" + element.element + "_1.png";                        element.style = 'background:url(' + mouseoverImg + ')';                        element.render();                    },                    "mouseout": function (element) {                        var mouseoutImg = "./images/homepage/" + element.element + "_0.png";                        element.style = 'background:url(' + mouseoutImg + ')';                        element.render();                    }                }            });