自定义FileDownloadOutputStream失败

不知为何自定义FileDownloadOutputStream后

   FileDownloader.setupOnApplicationOnCreate(this)
                .maxNetworkThreadCount(5)
                .connectionCreator(new FileDownloadUrlConnection
                        .Creator(new FileDownloadUrlConnection.Configuration()
                        .connectTimeout(15_000) // set connection timeout.
                        .readTimeout(15_000) // set read timeout.
                        .proxy(Proxy.NO_PROXY) // set proxy
                ))
                .outputStreamCreator(new FileDownloadHelper.OutputStreamCreator() {
                    @Override
                    public FileDownloadOutputStream create(File file) throws IOException {
                        return new CustomFileDownloadRandomAccessFile.Creator().create(file);
                    }

                    @Override
                    public boolean supportSeek() {
                        return true;
                    }
                })
                .commit();

使用时,不会走我自定义的FileDownloadOutputStream,还是会走默认的FileDownloadRandomAccessFile
研读了一下代码无果,希望能帮忙解决,非常感谢