datefield日期选择框，设置最大值最小值边界

{
	    	  xtype:"datefield",
	    	  margin : '5 5 5 5',
	    	  id : 'startDate',
	    	  name : 'q_startDate',
	    	  format:"Y-m-d",   
	    	  fieldLabel:"起始时间", 
	    	  emptyText : "请选择",
	    	  editable: false,
	    	  columnWidth : 1/3,
	    	  maxValue:new Date() ,
	    	  listeners:{
					expand:function(){
						var endDate = ('endDate').getValue();
						if(endDate!=null){
							(endDate);
						}
					}
				}
	      },{
	    	  xtype:"datefield",
	    	  margin : '5 5 5 5',
	    	  id : 'endDate',
	    	  name:'q_endDate',
	    	  format:"Y-m-d",   
	    	  fieldLabel:"截止时间",
	    	  emptyText : "请选择",
	    	  editable: false,
	    	  columnWidth : 1/3,
	    	  maxValue:new Date(),
	    	  listeners:{
	    		  expand:function(){
						var startDate = ('startDate').getValue();
						if(startDate!=null){
							(startDate);
						}
					}
				}
	      }