为什么ext.window里折线图不显示？新手求关照！

createfor: function(){
var ndtjStore = new Ext.data.JsonStore({

fields:['name','num1','num2'],
data:[
{name:'一月',num1:350,num2:300},

{name:'二月',num1:200,num2:150},

{name:'三月',num1:150,num2:200},

{name:'四月',num1:50,num2:10},

{name:'五月',num1:350,num2:400},

{name:'六月',num1:200,num2:150},

{name:'七月',num1:150,num2:100},

{name:'八月',num1:50,num2:100},

{name:'九月',num1:300,num2:300},

{name:'十月',num1:200,num2:250},

{name:'十一月',num1:150,num2:200},

{name:'十二月',num1:50,num2:100}

]

});
)
var win;
if(!win){
win = new Ext.Window({

title:'折线图',

layout:'fit',

closeAction:'hide',

plain: true,

height:400,

width:850,

items:[{

xtype:'linechart',

url:contextPath+ '/resources/ext3/resources/charts.swf',

store:ndtjStore,

xfield: 'name',

renderTo: ndtjDiv,
//yField:'alarmCount',

series: [
{type:'line',displayName: 'name',yField: 'num1',style: {color: 0x15428B}},
{type:'line',displayName: 'name',yField: 'num2',style: {color: 0x15428B}

}]

}]
});

win.show();
};
}