private void upLoadOnClick(View v) {
  String upUrl = "/mnt/sdcard/pic/test.jpg";//指定要上传的文件
  final ProgressDialog dia = new ProgressDialog(this);
  dia.setMessage("加载中....");
  dia.show();
  RequestParams params = new RequestParams(upUrl);
  params.addBodyParameter("file", new File(upUrl));
  x.http().post(params, new Callback.CommonCallback<String>() {
   @Override
   public void onSuccess(String result) {
    //加载成功回调，返回获取到的数据
    Log.i(TAG, "onSuccess: " + result);
   }

   @Override
   public void onFinished() {
    dia.dismiss();//加载完成
   }

   @Override
   public void onCancelled(CancelledException cex) {

   }

   @Override
   public void onError(Throwable ex, boolean isOnCallback) {

   }
  });
 }

 public void setRequestBody(RequestBody requestBody) {
  this.requestBody = requestBody;
 } 

 private void generateContentType() {
  String boundaryPostfix = Double.toHexString(Math.random() * 0xFFFF);
  boundaryPostfixBytes = boundaryPostfix.getBytes();
  contentType = "multipart/form-data; boundary=" + new String(BOUNDARY_PREFIX_BYTES) + boundaryPostfix;
 }

//参数分别是要传入的数据，和数据编码类型
 public MultipartBody(List<KeyValue> multipartParams, String charset) {
  if (!TextUtils.isEmpty(charset)) {
   this.charset = charset;
  }
  this.multipartParams = multipartParams;
  generateContentType();
  ...
 }

  //创建List<KeyValue>对象
  List<KeyValue> list = new ArrayList<>();
  //给list中添加数据，filePah是上传的文件路径，比如sd卡中图片
  list.add(new KeyValue("file", new File(filePah)));//文件流数据
  //其它参数，根据项目而定，比如我的项目中要传入的参数是json格式的
  list.add(new KeyValue("parameters", json.toString()));
  //创建MultipartBody
   MultipartBody body = new MultipartBody(list, "UTF-8");
   //添加请求参数
  params.setRequestBody(body); 

//要传递给服务器的json格式参数
JSONObject json = new JSONObject();
  try {
   json.put("devId", id);
   json.put("devName", devName);
   json.put("keyWord", keyWord);
  } catch (JSONException e) {
   e.printStackTrace();
  }
  //构建RequestParams对象，传入请求的服务器地址URL
  RequestParams params = new RequestParams(Constants.UPLOAD_FILE);
  params.setAsJsonContent(true);
  List<KeyValue> list = new ArrayList<>();
  list.add(new KeyValue("file", new File(filePah)));
  list.add(new KeyValue("parameters", json.toString()));
  MultipartBody body = new MultipartBody(list, "UTF-8");
  params.setRequestBody(body);
  x.http().post(params, new org.xutils.common.Callback.CommonCallback<String>() {
   @Override
   public void onSuccess(String result) {
    LogUtil.e("请求结果：" + result);
   }

   @Override
   public void onFinished() {
    //上传完成
   }

   @Override
   public void onCancelled(CancelledException cex) {
   //取消上传
   }

   @Override
   public void onError(Throwable ex, boolean isOnCallback) {
   //上传失败
    LogUtil.e("请求失败：" + ex.toString());

   }
  });