selenium用java选中ul的最后一个li元素里内容

<ul style="max-height: 230px; overflow-y: auto;" class="dropdown-menu inner selectpicker" role="menu">
	<li class="" rel="0"><a tabindex="0" class="" style=""><span class="text">Please Choose</span></a></li>
	<li class="" rel="1"><a tabindex="0" class="" style=""><span class="text">QQQQ</span></a></li>
	<li class="" rel="2"><a tabindex="0" class="" style=""><span class="text">PPPP</span></a></li>
	<li class="" rel="3"><a tabindex="0" class="" style=""><span class="text">abc</span></a></li>
	<li class="" rel="4"><a tabindex="0" class="" style=""><span class="text">aaaaaaaa</span></a></li>
</ul>

driver.findElement(By.xpath("(//ul[@class='dropdown-menu inner selectpicker']/li)[last()]/a/span[@class='text']")).click();

xpath文档链接 http://www.w3.org/TR/xpath/

这里需要注意，如果页面中有两个<ul><li>...</li></ul>，需要先定位到特定的ul，不然li[last()]会始终选择当前页面的最后一个li