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/toolbarIcon/edit.png) !important;
}
/*发布*/
.release {
background-image: url(../images/toolbarIcon/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({ 
         url: contextPath +'/system/lxdmglAction.do?method=getKbkg', 
         /*
         success: function(request){
         },
         failure: function(request){
         },
         */ 
         params: { kva: v} 
      }); 
        } 
                     
     Ext.Ajax.request({ 
      <a href="contextPath">url:contextPath</a> +'/system/lxdmglAction.do?method=getKbkgValue', 
      success:function(request){ 
       rs=Ext.decode(request.responseText); 
       if (rs=="1") { 
        Ext.getCmp("_kbkg").setText("关闭课表"); 
        Ext.getCmp("_kbkg").setIconClass('lock'); 
       } 
      }/*,
      failure:function(request){
       Ext.Msg.alert("加载课表开关失败，请重试！");
      }*/ 
     });