HighPriorityThemeNegotiator.php

<?php

declare (strict_types=1);
namespace Drupal\theme_test\Theme;

use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Theme\ThemeNegotiatorInterface;

/**
 * Implements a test theme negotiator which was configured with a high priority.
 */
class HighPriorityThemeNegotiator implements ThemeNegotiatorInterface {
  
  /**
   * {@inheritdoc}
   */
  public function applies(RouteMatchInterface $route_match) {
    return $route_match->getRouteName() == 'theme_test.priority';
  }
  
  /**
   * {@inheritdoc}
   */
  public function determineActiveTheme(RouteMatchInterface $route_match) {
    return 'starterkit_theme';
  }

}