Activity.java

...
if(BuildConfig.DEBUG) {
    Log.i("Key", SigningKey.getCertificateMD5Fingerprint(this));
}
...

SigningKey.java

public class SigningKey {

    /**
     * Get the MD5 fingerprint required for application authentication on the server to set up security profiles
     * @param context any Context from the running application
     * @return the string equivalent of the MD5 fingerprint
     */
    public static String getCertificateMD5Fingerprint(Context context) {
        PackageManager pm = context.getPackageManager();
        String packageName = context.getPackageName();
        int flags = PackageManager.GET_SIGNATURES;
        PackageInfo packageInfo = null;
        try {
            packageInfo = pm.getPackageInfo(packageName, flags);
        } catch (PackageManager.NameNotFoundException e) {
            e.printStackTrace();
        }
        Signature[] signatures = packageInfo.signatures;
        byte[] cert = signatures[0].toByteArray();
        InputStream input = new ByteArrayInputStream(cert);
        CertificateFactory cf = null;
        try {
            cf = CertificateFactory.getInstance("X509");
        } catch (CertificateException e) {
            e.printStackTrace();
        }
        X509Certificate c = null;
        try {
            c = (X509Certificate) cf.generateCertificate(input);
        } catch (CertificateException e) {
            e.printStackTrace();
        }
        String hexString = null;
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            byte[] publicKey = md.digest(c.getEncoded());
            hexString = byte2HexFormatted(publicKey);
        } catch (NoSuchAlgorithmException e1) {
            e1.printStackTrace();
        } catch (CertificateEncodingException e) {
            e.printStackTrace();
        }
        return hexString;
    }

    /**
     * Convert the resulting byte array into a string for submission
     * @param arr the byte array supplied by getCertificateMD5Fingerprint
     * @return the string equivalent
     */
    public static String byte2HexFormatted(byte[] arr) {
        StringBuilder str = new StringBuilder(arr.length * 2);
        for (int i = 0; i < arr.length; i++) {
            String h = Integer.toHexString(arr[i]);
            int l = h.length();
            if (l == 1) h = "0" + h;
            if (l > 2) h = h.substring(l - 2, l);
            str.append(h.toUpperCase());
            if (i < (arr.length - 1)) str.append(':');
        }
        return str.toString();
    }
}