重定义extjs中button被点击后的样式

1.
var btn = new Ext.Button({text:'ddd'});
btn.on('',function(b){
    b.addClass('newCSS');
});

2.
/*编辑*/
.edit {
background-image: url(../images/易做图Icon/edit.png) !important;
}
/*发布*/
.release {
background-image: url(../images/易做图Icon/release.png) !important;
}

var btn= new Ext.ButtonGroup({

id : 'edit',
       text : '编辑',
       handler : onRelease,
       iconCls : 'edit'//样式图片
});
function onRelease(){
btn.setIconClass('release');//更改图片
btn.setText('发布');
}

[javascript]
{
                                            id:'_kbkg',
                                            xtype: 'button',
                                            text:'打开课表',
                                            iconCls:'unlock',
                                            listeners: {
                                                'click': function(t){
                                                    var text = t.getText();
                                                    if(text == "打开课表"){
                                                        t.setText("关闭课表");
                                                        t.setIconClass('lock');
                                                        KbCheck(1);
                                                    }if(text == '关闭课表'){
                                                        t.setText("打开课表");
                                                        t.setIconClass('unlock');
                                                        KbCheck(0);
                                                    }

                                                }
                                            }
                                        }
[javascript]

[javascript]
Ext.getCmp("xn_label").setText(" 学年: " + xn);
                    Ext.getCmp("xq_label").setText(" 学期: " + xq);

     //课表开关
     function KbCheck(v){
      Ext.Ajax.request({

补充：web前端 , JavaScript ,