写一个xml文件到磁盘的方法

/**
         * 往磁盘上写一个xml文件
         * 
         * <?xml version="1.0" encoding="UTF-8" standalone="true"?> //文档的神明
            <persons> //标签tag
                <person id=“18"> //ID是person标签的一个属性
                    <name>allen</name>
                    <age>36</age>
                </person>
                <person id=“28">
                    <name>james</name>
                    <age>25</age>
                    </person> 
            </persons>

         * 
         */
        //XmlPullParser parser = Xml.newPullParser();// 解析xml
        XmlSerializer serializer = Xml.newSerializer();// xml序列化工具类
        File f = new File(Environment.getExternalStorageDirectory(), "persons.xml");
        try {
            FileOutputStream fos = new FileOutputStream(f);
            serializer.setOutput(fos, "utf-8");//给序列化工具设置输出路径和输出编码
            serializer.startDocument("utf-8", true);
            serializer.startTag(null, "persons");
            //person 标签
            serializer.startTag(null, "person");
            serializer.attribute(null, "id", "18");
            serializer.startTag(null, "age");
            serializer.text("lx");
            serializer.endTag(null, "age");
            serializer.endTag(null, "person");
            serializer.endTag(null, "persons");
            serializer.endDocument();