How to save an audio file in storage in Android Studio?

I am working on a Piano App in android which has a record functionality. It uses the device mic to record and then saves the recorded file to the device memory.

How do I correctly save a audio file in storage in an android App? I am unable to save the file inside the device. Currently I am getting a Toast message "Added file null" after I stop the recording. The uri object is giving me a null value in the Toast message. What am I doing wrong?

   private void startRecording() throws IOException {

        try {
            String direPath = context.getExternalFilesDir(null).getAbsolutePath();
            String filePath = direPath + "/recording";
            audioFile = new File(filePath);
        } catch (Exception e) {
            Log.e("Error Tag", "external storage access error " + e.getMessage());
            return;
        }


        mediaRecorder = new MediaRecorder();
        mediaRecorder.setAudioSource(MediaRecorder.AudioSource.DEFAULT);
        mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
        mediaRecorder.setOutputFile(audioFile.getAbsolutePath());

            mediaRecorder.prepare();
            mediaRecorder.start();

}

 private void stopRecording(){
        if(mediaRecorder !=  null)
            mediaRecorder.stop();

        saveToDisk();
    }

    public void saveToDisk() {
        ContentResolver contentResolver = context.getContentResolver();
        ContentValues values = new ContentValues();
        {
            long current = System.currentTimeMillis();
            values.put(MediaStore.Audio.Media.TITLE, "audio" + audioFile.getName());
            values.put(MediaStore.Audio.Media.DATE_ADDED, (int) (current / 1000));
            values.put(MediaStore.Audio.Media.MIME_TYPE, "audio/mpeg");
         
            values.put(MediaStore.Audio.Media.DATA, audioFile.getAbsolutePath());
        }
            Uri uri = contentResolver.insert(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, values);
            sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, uri));
             Toast.makeText(this, "Added File " + uri, Toast.LENGTH_LONG).show();
}