How to update progress bar from retrofit enqueue method in android

Question

I am facing an issue I am using retrofit2 for file downloading and I want to show file downloading progress from 1% to 100%. The progress bar is only updated to 100% when file downloaded completely but I want the progress of file shown while the file is downloading here is the code I have tried so far. Looking forward to your solutions.

   private void downloadPdfFile() {

    progressBar.setVisibility(View.VISIBLE);
    progressBar.setMax(100);
    progressBar.setProgress(0);
    Call<ResponseBody> response = mPdfDownloadService.downloadPdfBook(fileName);

    response.enqueue(new Callback<ResponseBody>() {
        @Override
        public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
            if (response.isSuccessful()) {


                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {


                        saveToDisk(response.body());
                    }
                });

                progressBar.setVisibility(View.GONE);
                Toast.makeText(BooksByClassActivity.this, "File downloaded Successfully ", Toast.LENGTH_SHORT).show();
            }
        }


        @Override
        public void onFailure(Call<ResponseBody> call, Throwable t) {
            Toast.makeText(BooksByClassActivity.this, "Unable to connect", Toast.LENGTH_SHORT).show();
            progressBar.setVisibility(View.GONE);
        }
    });
}

//Method to download Pdf file and to save in phone storage

    private boolean saveToDisk(ResponseBody body) {
    try {
        // todo change the file location/name according to your needs
        File pdfFile = new File(getFilesDir() + File.separator + fileName);

        InputStream inputStream = null;
        OutputStream outputStream = null;
        long progress = 0;
        int count;
        byte[] data = new byte[4096];

        try {

            long fileSize = body.contentLength();
            inputStream = body.byteStream();
            outputStream = new FileOutputStream(pdfFile);


            while ((count = inputStream.read(data)) != -1) {
                progress += count;

                long finalProgress = progress;
                Log.d("Progress", "" + (int) ((finalProgress * 100) / fileSize));
                progressBar.setProgress((int) ((finalProgress * 100) / fileSize));

                outputStream.write(data, 0, count);

            }

            outputStream.flush();

            return true;
        } catch (IOException e) {
            return false;
        } finally {
            if (inputStream != null) {
                inputStream.close();
            }

            if (outputStream != null) {
                outputStream.close();

            }
        }
    } catch (IOException e) {
        return false;
    }
}