ExtJs 4中 Ext.Ajax.request提交实现waitMsg等待提示效果

//submitForm为form表单
var myMask = new Ext.LoadMask(Ext.getBody(),{msg:"请稍等,正在导入..."});
myMask.show();
Ext.Ajax.request({ url:"uploadAction",
 method:"POST",
params:{
 id:id
},
success:function(){
if (myMask != undefined){ myMask.hide();}
Ext.Msg.alert("消息","文件导入成功!");
 },
failure:function(){
if (myMask != undefined){ myMask.hide();}
 Ext.Msg.alert("消息","文件导入失败!");
}
});