有时候Android的怪事真是太神奇了（和有趣的..）。我解决了这种方式：

Sometimes Android weirdness is really amazing (and amusing..). I solved it this way:

一）在XML中定义一个子占位符是这样的：

a) Define in XML a submenu placeholder like this:

<item android:visible="true" android:id="@+id/m_area"
   android:titleCondensed="Areas"
   android:title="Areas"
   android:icon="@drawable/restaur"
   android:enabled="true"> 
   <menu>
    <item android:id="@+id/item1" android:title="Placeholder"></item>
   </menu>
</item>

二）获取子菜单项OnCreateOptionsMenu，将其清除，并添加我的子菜单项，像这样的：

b) Get sub menu item in OnCreateOptionsMenu, clear it and add my submenu items, like this:

    public boolean onCreateOptionsMenu(Menu menu) { 
            MenuInflater inflater = getMenuInflater();
            inflater.inflate(R.menu.mapoptions, menu);

            int idx=0;
            subm = menu.getItem(MYITEM_INDEX).getSubMenu(); // get my MenuItem with placeholder submenu
            subm.clear(); // delete place holder

            while(true)
            {
                anarea = m_areas.GetArea(idx); // get a new area, return null if no more areas
                if(anarea == null)
                    break;
                subm.add(0, SUBAREASID+idx, idx, anarea.GetName()); // id is idx+ my constant
                ++idx;
            }
}