安卓 android XML Dom node.getNodeValue 返回 null

org.w3c.dom.Document doc = DocumentBuilderFactory.newInstance().newDocumentBuilder()
        .parse(new ByteArrayInputStream(xml.getBytes()));
NodeList nodes = doc.getElementsByTagName("tptz:Preset");
for (int i = 0; i < nodes.getLength(); i++) {
    Node node = nodes.item(i);
    Log.i(TAG, node.getNodeName + "=>" + node.getTextContent()
}