combobox只能显示4个选项么

struct rtgui_listbox_item items[] = 
{
    {"1", RT_NULL},
    {"2", RT_NULL},
    {"3", RT_NULL},
    {"4", RT_NULL},
    {"5", RT_NULL},
    {"6", RT_NULL},
};
......
    box = rtgui_combobox_create(items, 6, &rect);
    // view是一个container控件，调用add_child方法添加这个box控件
    rtgui_container_add_child(RTGUI_CONTAINER(view), RTGUI_WIDGET(box));
......