How to convert a file to base 64 (like .pdf,.txt) in Android?

this method worked for me

String encodeFileToBase64Binary = encodeFileToBase64Binary(yourFile);    

private String encodeFileToBase64Binary(File yourFile) {
    int size = (int) yourFile.length();
    byte[] bytes = new byte[size];
    try {
        BufferedInputStream buf = new BufferedInputStream(new FileInputStream(yourFile));
        buf.read(bytes, 0, bytes.length);
        buf.close();
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    String encoded = Base64.encodeToString(bytes,Base64.NO_WRAP);
    return encoded;
}

All you have to do is read the file to a byte array, and then use Base64.encodeToString(byte[], int) to convert it to a Base64 string.