extjs文件上传对话框显示后，页面出现空白的问题

 1 Ext.define('MyApp.view.MyPanel', {
 2     extend: 'Ext.panel.Panel',
 3 
 4     height: 375,
 5     width: 557,
 6     layout: {
 7         type: 'border'
 8     },
 9     title: 'My Panel',
10 
11     initComponent:  function() {
12          var me =  this;
13 
14         Ext.applyIf(me, {
15             items: [
16                 {
17                     xtype: 'gridpanel',
18                     title: 'My Grid Panel',
19                     region: 'center',
20                     columns: [
21                         {
22                             xtype: 'gridcolumn',
23                             dataIndex: 'string',
24                             text: 'String'
25                         },
26                         {
27                             xtype: 'numbercolumn',
28                             dataIndex: 'number',
29                             text: 'Number'
30                         },
31                         {
32                             xtype: 'datecolumn',
33                             dataIndex: 'date',
34                             text: 'Date'
35                         },
36                         {
37                             xtype: 'booleancolumn',
38                             dataIndex: 'bool',
39                             text: 'Boolean'
40                         }
41                     ],
42                     viewConfig: {
43 
44                     }
45                 },
46                 {
47                     xtype: 'container',
48                     height: 110,
49                     layout: {
50                         type: 'border'
51                     },
52                     region: 'north',
53                     items: [
54                         {
55                             xtype: 'form',
56                             bodyPadding: 10,
57                             title: '',
58                             region: 'center',
59                             items: [
60                                 {
61                                     xtype: 'filefield',
62 id:'upfile',//需要通过ID，获得控件的form,在执行提交动作
63                                     width: 534,
64                                     fieldLabel: 'Label',
65                                     anchor: '100%'
66                                 },
67                                 {
68                                     xtype: 'button',
69                                     text: 'MyButton'
70                                 }
71                             ]
72                         }
73                     ]
74                 }
75             ]
76         });
77 
78         me.callParent(arguments);
79     }
80 
81 });

Ext.getCmp('upfile').getForm().submit({   
            waitTitle : '系统提示',
            waitMsg : '正在上传，请等待...',// 动作发生期间显示的文本信息
            url: 'Fileupload.aspx',//fileUploadServlet   
            method : 'POST',// 表单提交方式
            params : request,
            success: onSuccess,
            failure: onFailure
    });