WooCommerce：在可变产品页面中显示当前的SKU和GTIN

Question

Is there a way to display the current product SKU and GTIN in a variable product page? Right now I'm using the following code, but it only works for simple products without variations:

add_action('woocommerce_single_product_summary', 'show_sku_and_gtin');
function show_sku_and_gtin() {
  global $product, $post; 
  echo '<p>SKU: '.$product->sku.'</p>';
  // In my case, GTIN is a custom field called "barcode"
  echo '<p>GTIN: '.get_post_meta($post->ID, 'barcode', 1).'</p>';                    
}

I'd like it to update the SKU and GTIN dynamically whenever I choose a different product variation in the product page.