Xamarin forms x Android: OnActivityResult just fire on MainActivity

Trying to use DependencyService to start Card.IO component, the problem is that, the event OnActivityResult only fires on the MainActivity, am I doing something wrong or it's a Xamarin Forms restriction?

Here is the code:

public class CardScanner : FormsApplicationActivity, PedirComida.Controls.ICardScanner
    {
        TaskCompletionSource<string> aRetornar;

        public async Task<string> ScanAsync()
        {
            aRetornar = new TaskCompletionSource<string>();
            var intent = new Intent(Forms.Context, typeof(CardIOActivity));
            intent.PutExtra(CardIOActivity.ExtraRequireExpiry, true);
            intent.PutExtra(CardIOActivity.ExtraRequireCvv, true);
            intent.PutExtra(CardIOActivity.ExtraRequirePostalCode, false);
            intent.PutExtra(CardIOActivity.ExtraUseCardioLogo, true);
            ((Activity)Forms.Context).StartActivityForResult(intent, 101);
            return await aRetornar.Task;
        }

        protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
        {
            base.OnActivityResult(requestCode, resultCode, data);

            if (data != null)
            {
                var card = data.GetParcelableExtra(CardIOActivity.ExtraScanResult).JavaCast<CreditCard>();
                aRetornar.SetResult(card.FormattedCardNumber);
            }
        }

    }