/**
* 多圖上傳
*/

    Map<String, RequestBody> requestBodyMap = new HashMap<>();
    for (int i = 0; i < fileNames.size(); i++) {
        File file = new File(fileNames.get(i));
        RequestBody requestBody = RequestBody.create(MediaType.parse("image/png"), file);
        // 這里前面一部分是服務(wù)器要求傳的key("file")，加上一個(gè)i,就可以動(dòng)態(tài)設(shè)置key的長(zhǎng)度
        requestBodyMap.put("file" + i + "\"; filename=\"" + file.getName(), requestBody);
    }
    Observable<Response<Void>> observable = BaseUrlApi.getApiBaseService().uploadFile(requestBodyMap, feedbackBean.getId(), 0);
    HttpMethods.toSubscribe(observable, new BaseObserver<Response<Void>>(getSupportFragmentManager()) {
        @Override
        protected void onBaseNext(Response<Void> data) {
            commitSuccess();
        }

        @Override
        protected void onBaseError(Throwable t) {
            super.onBaseError(t);
        }
    });
}

/**
* 多圖上傳接口
*/

@Multipart
@POST("feedbacks/uploadFile")
Observable<Response<Void>> uploadFile(@PartMap Map<String, RequestBody> requestBodyMap, @Query("feedbackId") int feedbackId, @Query("fileType") int fileType);

https://blog.csdn.net/danceinkeyboard/article/details/78096926

http://simontse.github.io/2016/06/07/RRUploadPic/