QtCreator does not display "enabled" property correctly.

When I creator a widget,and put some buttons in it.and then I set the widget disabled in QtCreator's designer. Then I change the buttons' "enabled" property.There are two problems.1,every buttons in the same widget show th same enabled state.If I change one's enabled property,other's will be changed at same time.2,when I change one's to true,the enabled property is still false.And I can not change it to true except change the code in ui_xxx.h