sencha touch 2中list如何动态添加或移除一个button

listeners: {
                el: {
                    tap: function(e, target){
                        self.query('button[action=desktop_set_cancel_btn]')[0].setText('完成');
                        var uiName = $(target).parent('.ui_list_item').attr('ths_ui_name');
                        $(target).parent('.ui_list_item').remove();
                        self.doLayout();
                        self.query('button[thsUIName=' + uiName + ']')[0].setDisabled(false);
                    },
                    delegate: '.item_del',
                },
            },