ShouldQueue的Laravel事件侦听器未定义属性错误

我的应用程序中有一个事件设置，它在用户注册时发送激活电子邮件。它在没有ShouldQueue接口的情况下可以完美工作。然而，当我添加implements ShouldQueue时，我得到了未定义的属性错误：

未定义的属性：App''Events''User''UserCreated:：$User

我使用的代码如下：

<?php
namespace App'Listeners'User;
use App'Events'User'UserCreated;
use Illuminate'Queue'InteractsWithQueue;
use Illuminate'Contracts'Queue'ShouldQueue;
use App'Repos'Email'EmailTemplateRepoInterface;
use App'Repos'User'UserRepoInterface;
use Request, Mail, DbView;
class UserCreatedEmail implements ShouldQueue
{
    /**
     * Create the event listener.
     *
     * @return void
     */
    public function __construct(EmailTemplateRepoInterface $template)
    {
        $this->template = $template;
    }
    /**
     * Handle the event.
     *
     * @param  UserCreated  $event
     * @return void
     */
    public function handle(UserCreated $event)
    {
        $user = $event->user;
        if($user)
        {
            if(!$user->status)
            {
                $user->activation_url = Request::root().'/activate/'.$user->activation_code;
                $template = $this->template->findTemplateByName('new_user_activation');
                $userArr = $user->toArray();
            }
            Mail::queue([], [], function ($message) use ($template, $userArr) 
            {
                $message->to($userArr['email'])
                    ->subject($template->subject)
                    ->setBody(DbView::make($template)->with($userArr)->render(), 'text/html');
            });
        }
    }
}

编辑

这也是UserCreated类：

<?php
namespace App'Events'User;
use App'Events'Event;
use Illuminate'Queue'SerializesModels;
use Illuminate'Contracts'Broadcasting'ShouldBroadcast;
class UserCreated extends Event
{
    use SerializesModels;
    /**
     * Create a new event instance.
     *
     * @return void
     */
    public function __construct($user, $row, $request)
    {
        $this->user = $user;
        $this->request = $request;
        $this->row = $row;
    }
    /**
     * Get the channels the event should be broadcast on.
     *
     * @return array
     */
    public function broadcastOn()
    {
        return [];
    }
}

有人能解释为什么当我尝试对电子邮件进行排队时会发生这种情况吗