Convert mp3 file to a string.

To convert a mp3 file into a string, we first have to change it to byte array and then to the string.

The following function can convert the file to an array:

public String convert() {
    String outputFile =
         Environment.getExternalStorageDirectory().getAbsolutePath() + "/recorded_audio.mp3";
//It will save the mp3 file in phone's internal memory directory.
    byte[] bytearray = new byte[0];
    try {
        InputStream inputStream =
                getContentResolver().openInputStream(Uri.fromFile(new File(outputFile)));

        bytearray = new byte[inputStream.available()];
        bytearray = toByteArray(inputStream);

        Toast.makeText(this, "" + bytearray, Toast.LENGTH_LONG).show();
    } catch (Exception e) {
        e.printStackTrace();
    }

   return bytearray;
}

The Toast in the above function will not show you the exact byte array generated. If you want to see the byte array,

you use the following code:

String actualArray = Arrays.toString(bytearray);

This String will give you the actual array.

Reduce using Base64:

String reducedArray = Base64.encodeToString(bytearray,Base64.NO_WRAP);

This will reduce the string upto an extent. To reduce further you should use the function given below.

Reduce using hexString:

String lastString = bytesToHexString(bytearray);
public static String bytesToHexString(byte[] in) {
    final StringBuilder builder = new StringBuilder();
    for(byte b : in) {
        builder.append(String.format("%02x", b));
    }
    return builder.toString();
}

Convert HexString back to byte array:

public static byte[] hexStringToByteArray(String s) {
    int len = s.length();
    byte[] data = new byte[len / 2];
    for (int i = 0; i < len; i += 2) {
        data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
                + Character.digit(s.charAt(i+1), 16));
    }
    return data;
}

Convert byte array to mp3 file:

Declare this line above onCreate function.

private MediaPlayer mediaPlayer = new MediaPlayer();

Use this function to get mp3 file back.

private void mp3File(byte[] bytearray) {
    try {
        File tempFile = File.createTempFile("mobile", "mp3", getCacheDir());
        tempFile.deleteOnExit();
        FileOutputStream fos = new FileOutputStream(tempFile);
        fos.write(bytearray);
        fos.close();
mediaPlayer.reset();

        FileInputStream fis = new FileInputStream(tempFile);
        mediaPlayer.setDataSource(fis.getFD());

        mediaPlayer.prepare();
        mediaPlayer.start();
    } catch (IOException ex) {
        String s = ex.toString();
        ex.printStackTrace();
    }
}

Get the full code: https://github.com/Himanshu-Choudhary-07/voicemail