xml文件写的问题

[xinqiao2008]

const char szFileNameE[128] = "a.xml";
TiXmlDocument xDocE;
TiXmlElement xRootE("Root");
TiXmlElement xDetectRgnE("Channel-0");
xDetectRgnE.SetAttribute("Accuracy", "100");
xRootE.InsertEndChild(xDetectRgnE);
xDocE.InsertEndChild(xRootE);
xDocE.SaveFile(szFileNameE);
//a.xml
<Root>
<Channel-0 Accuracy="25" />
<Channel-1 Accuracy="25" />
<Channel-2 Accuracy="25" />
<Channel-3 Accuracy="25" />
<Channel-4 Accuracy="25" />
<Channel-5 Accuracy="25" />
<Channel-6 Accuracy="25" />
<Channel-7 Accuracy="25" />
</Root>

//本想只更改一行的数据，却变成了只剩一行了。
<Root>
<Channel-0 Accuracy="100" />
</Root>