XML定义三级菜单，比如
<first name="fir" value="一级菜单1>
<second name="sec" value="二级菜单1">
<third>三级菜单1</third>
<third>三级菜单2</third>
</second>
<second name="sec" value="二级菜单2">
<third>三级菜单3</third>
<third>三级菜单4</third>
</second>
</first>
<first name="fir" value="一级菜单2>
<second name="sec" value="二级菜单3">
<third>三级菜单5</third>
<third>三级菜单6</third>
</second>
<second name="sec" value="二级菜单4">
<third>三级菜单7</third>
<third>三级菜单8</third>
</second>
</first>
新建一个XmlManager类，和三个View代表三个菜单View页面，一级菜单页面则解析first标签的value赋值给一级菜单，二级菜单则根据点击的一级菜单项进行解析相应的二级菜单，比如一级菜单选择的是"一级菜单1"，则解析一级菜单value是"一级菜单1"标签下的二级菜单列表，同理去实现第三级菜单的现实
