如何在使用PayPal未来付款时获得帐户参考？

Question

您好我想在我的Android应用程序中添加多个paypal帐户，用户必须在付款时从已保存的帐户中进行选择。为此我使用paypal的Future支付选项

@Override
protected void onActivityResult (int requestCode, int resultCode, Intent data) {
if (resultCode == Activity.RESULT_OK) {
    PayPalAuthorization auth = data
            .getParcelableExtra(PayPalFuturePaymentActivity.EXTRA_RESULT_AUTHORIZATION);
    if (auth != null) {
        try {
            String authorization_code = auth.getAuthorizationCode();

            sendAuthorizationToServer(auth);

        } catch (JSONException e) {
            Log.e("FuturePaymentExample", "an extremely unlikely failure occurred: ", e);
        }
    }
} else if (resultCode == Activity.RESULT_CANCELED) {
    Log.i("FuturePaymentExample", "The user canceled.");
} else if (resultCode == PayPalFuturePaymentActivity.RESULT_EXTRAS_INVALID) {
    Log.i("FuturePaymentExample",
            "Probably the attempt to previously start the PayPalService had an invalid PayPalConfiguration. Please see the docs.");
}
}

通过这种方式我获得了身份验证代码，但我还需要一些帐户参考，以便为用户提供帐户选择选项。如何使用auth代码获取电子邮件参考，还是应该采取其他方法？ 谢谢！