UserTrackerTab.php

<?php

namespace Drupal\tracker\Plugin\Menu;

use Drupal\Core\Menu\LocalTaskDefault;
use Drupal\Core\Routing\RouteMatchInterface;

/**
 * Provides route parameters needed to link to the current user tracker tab.
 */
class UserTrackerTab extends LocalTaskDefault {
  
  /**
   * Current user object.
   *
   * @var \Drupal\Core\Session\AccountInterface
   */
  protected $currentUser;
  
  /**
   * Gets the current active user.
   *
   * @todo: https://www.drupal.org/node/2105123 put this method in
   *   \Drupal\Core\Plugin\PluginBase instead.
   *
   * @return \Drupal\Core\Session\AccountInterface
   */
  protected function currentUser() {
    if (!$this->currentUser) {
      $this->currentUser = \Drupal::currentUser();
    }
    return $this->currentUser;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getRouteParameters(RouteMatchInterface $route_match) {
    return [
      'user' => $this->currentUser()
        ->Id(),
    ];
  }

}