java lang ..空指针异常

Question

下面是我的演示代码：

 @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String, String> params = new HashMap<>();
                params.put("sno", sno);
                params.put("topic_id", topic_id);


                return params;
            }

           @Override
            protected Map<String, VolleyMultipartRequest.DataPart> getByteData() {
                Map<String, DataPart> up_params = new HashMap<>();
               String file_name = getFileName(imageUri);
               File file = new File(selectfilePath);
                up_params.put("attach_files", new DataPart(selectfilePath, file_name, "*/*"));

                return up_params;
            }




        };
        volleyMultipartRequest.setRetryPolicy(
                new DefaultRetryPolicy(
                        0,
                        -1,
                        DefaultRetryPolicy.DEFAULT_BACKOFF_MULT
                )
        );

        //adding the request to volley
      //  Volley.newRequestQueue(this).add(volleyMultipartRequest);
        VolleySingleton.getInstance(getBaseContext()).addToRequestQueue(volleyMultipartRequest);

我成功上传了图片，但是当我允许上传所有类型的文件时，出现错误空指针异常，我尝试了很多事情。

如何在android中上传所有类型的文件？