_adyen.html.erb

<% content_for :head do %>
  <%= javascript_include_tag 'spree/checkout/payment/adyen.js' %>
<% end %>

<p>
  You'll be redirected to Adyen Hosted Payment Pages. After completing the
  payment form you'll be back to the store.
</p>

<%= content_tag :div, "", id: 'adyen-hpp-details', data: {
  url: directory_adyen_hpp_path(
    order_id: @order.id,
    payment_method_id: payment_method.id) } %>

<script type="text/javascript">
$(function() {
  var spreePaymentRadio = $("#checkout_form_payment input:radio")

  var hideCheckoutButtonForAdyen = function() {
    if ($("#checkout_form_payment input:radio:checked").val() == <%= payment_method.id %>) {
      $("#checkout_form_payment .form-buttons").hide();
    } else {
      $("#checkout_form_payment .form-buttons").show();
    }
  }

  spreePaymentRadio.change(function() {
    hideCheckoutButtonForAdyen();
  });

  hideCheckoutButtonForAdyen();
});
</script>