private String body;
private String number;
private int type;
private long id;

public static void backUpXml(File file, List<XmlInfo> smsInfos) throws Exception
    {
        //xml文件的序列号器  帮助生成一个xml文件
        FileOutputStream fos = new FileOutputStream(file);
        //获取到xml的序列号
        XmlSerializer serializer = Xml.newSerializer();
        //序列化初始化
        serializer.setOutput(fos, "utf-8");
        //创建xml
        serializer.startDocument("utf-8", true);
        serializer.startTag(null, "smss");
        
        for(XmlInfo info : smsInfos)
        {
            serializer.startTag(null, "sms");
            serializer.attribute(null, "id", String.valueOf(info.getId()));
            
            serializer.startTag(null, "body");
            serializer.attribute(null, "body", info.getBody());
            serializer.endTag(null, "body");
            
            serializer.startTag(null, "number");
            serializer.text(info.getNumber());
            serializer.endTag(null, "number");
            
            serializer.endTag(null, "sms");
        }
        
        serializer.endTag(null, "smss");
        serializer.endDocument();
        
        fos.flush();
        fos.close();
    
    }

List<XmlInfo> xmlinfo = new ArrayList<XmlInfo>();
        
        XmlInfo xml1 = new XmlInfo("aaaa","12345678912",1,1);
        XmlInfo xml2 = new XmlInfo("bbbb","21987654321",1,2);
        XmlInfo xml3 = new XmlInfo("cccc","12345678912",1,3);
        
        xmlinfo.add(xml1);
        xmlinfo.add(xml2);
        xmlinfo.add(xml3);
        
        
        File file = new File(Environment.getExternalStorageDirectory(),"back.xml");
        //File file = new File(MainActivity.this.getFilesDir(),"back.xml");
        try {
            XmlManager.backUpXml(file, xmlinfo);
            Toast.makeText(this, "备份成功", 0).show();
        } catch (Exception e) {
            // TODO 自动生成的 catch 块
            e.printStackTrace();
            Toast.makeText(this, "备份失败", 0).show();
        }