采用自定义Body方式：（https://github.com/zhou-you/RxEasyHttp）
 File file = new File(dataM.get("path").toString());//imgUrl为图片位置
        RequestBody fileBody = RequestBody.create(MediaType.parse("application/json"), file);
        RequestBody requestBody = new MultipartBody.Builder()
                .setType(MultipartBody.FORM)
                .addFormDataPart("file", file.getName(), fileBody) 
                .build();

        EasyHttp.post(url)
                .headers("Authorization", dataM.get("token").toString())
                .timeStamp(true) 
                .requestBody(requestBody)
                .execute(commonResp);