extjs：fieldset-change收合图示

background-position

#plus-min.x-panel-collapsed .x-tool-toggle{
    background-position: 0 -240px !important; /*the plus sign*/
}
#plus-min .x-tool-toggle{
    background-position: 0 -255px !important; /*the minus sign*/
}

new Ext.form.FormPanel({
    renderTo : document.body,
    title : \"asdasd\",
    items :[{
            xtype:\'fieldset\',
            title: \'Plus Minus\',
            collapsible: true,
            id : \"plus-min\",
            html : \"asd\",
            height : 100
        }]
});