how to get a selectfield inside of a panel working (sencha touch)

I try to get a selectfield inside a floating, modal centerd panel working but when I click to select, the "mother"-panel closes and only the selection-panel of the selectfield stays.

if (!this.popup) {
                this.popup = new Ext.Panel({
                    floating: true,
                    modal: true,
                    centered: true,
                开发者_开发百科    width: 390,
                    height: heightOfPopUp,
                    styleHtmlContent: true,
                    scroll: 'vertical',
items: [{
                                xtype: 'selectfield',
                                name: 'options',
                                options: [
                                    {text: 'This is just a big select',  value: '1'},
                                    {text: 'Another select item', value: '2'}
                                ]
                          }]... 

what am I doing wrong?

thnx!

---

Try adding this to the panel options:

hideOnMaskTap: false,