public void StartListening(Context ctx, IFingerprintAuthCallback callback)
        {
            if (Listening)
            {
                return;
            }

            try
            {
                _spassFingerprint.StartIdentifyWithDialog(ctx, new IdentifyListener(callback, ctx, this), false);
                Listening = true;
            }
            catch (SpassInvalidStateException m)
            {
                callback.OnFingerprintError(m.Message);
            }
            catch (IllegalStateException ex)
            {
                callback.OnFingerprintError(ex.Message);
            }
        }
 public override void OnAuthenticationError(FingerprintState errorCode, ICharSequence errString)
 {
     _callback.OnFingerprintError(errString.ToString());
 }