why form with a upload filed opens a new window while submitting?

[lzm821029]

While I submit a form that doesn't contain the "filefield" xtype it works well.
But when a add the filefiled xtype.the form opens a new window that request to the community_save.do. How to prevent the form to opening a new window,just get the response and call my callback method "success"? form definition below:

xtype: 'form',
            url: 'community_save.do',
            bodyPadding: 5,
            items: [
                {
                    xtype: 'hiddenfield',
                    name : 'id',
                    fieldLabel: 'ID'
                },
                {
                    xtype: 'textfield',
                    name : 'name',
                    fieldLabel: '名称',
                    allowBlank: false
                },
                {
                    xtype: 'filefield',
                    name : 'map',
                    fieldLabel: '小区地图',
                    msgTarget: 'side',
                    buttonText: 'Choose a Image File'
                }]

handler code below:

saveCommunity: function(button) {
    var win    = button.up('window'),
        form   = win.down('form').getForm();

    if (form.isValid()) {
        form.submit({
            waitMsg: 'Uploading your map...', 
            success: function(form, action) {
               Ext.Msg.alert('提示', action.result.msg);
               win.close();
               this.loadActivities();
            },
            failure: function(form, action) {
                Ext.Msg.alert('提示', action.result.msg);
            },
            scope: this
        });
    }

},

Thanks a lot for your answer!!!

未命名.jpg

[arcan9ne]

Does this occur in all browsers?

[lzm821029]

yeah ,I think so . It opens a new window in firefox and post a request to about:blank in chrome. you can see the picture below.

chrome.jpg