Ext.form.ComboBox 提交始终获得displayField的值

var alertLevel = new Ext.form.ComboBox( {id:'cmb_alertLevel', hiddenName:"level",//提交到后台的input的name store: new Ext.data.SimpleStore({        fields: ['myId', 'displayText'],        data: [['0', 'Emergency'], ['1','Alert'],        ['2','Critical'],['3','Error'],        ['4','Warning'],['5','Notice'],        ['6','Informational'],['7','Debug']]            }),    valueField: 'myId',//option.value    displayField: 'displayText', //option.texttypeAhead : true,triggerAction : 'all',emptyText : '所有',mode: 'local',applyTo : 'alertLevel'});

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重要属性设置 hiddenName:'level'。??后台直接通过 String alertLevel = request.getParameter("level");获取值