View.php

<?php
/**
 *
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Sales\Controller\Adminhtml\Shipment\AbstractShipment;

use Magento\Backend\App\Action\Context;
use Magento\Backend\Model\View\Result\ForwardFactory;

abstract class View extends \Magento\Backend\App\Action
{
    /**
     * Authorization level of a basic admin session
     *
     * @see _isAllowed()
     */
    const ADMIN_RESOURCE = 'Magento_Sales::shipment';

    /**
     * @var ForwardFactory
     */
    protected $resultForwardFactory;

    /**
     * @param Context $context
     * @param ForwardFactory $resultForwardFactory
     */
    public function __construct(
        Context $context,
        ForwardFactory $resultForwardFactory
    ) {
        parent::__construct($context);
        $this->resultForwardFactory = $resultForwardFactory;
    }

    /**
     * Shipment information page
     *
     * @return \Magento\Backend\Model\View\Result\Forward
     */
    public function execute()
    {
        /** @var \Magento\Backend\Model\View\Result\Forward $resultForward */
        $resultForward = $this->resultForwardFactory->create();
        if ($this->getRequest()->getParam('shipment_id')) {
            $resultForward->setController('order_shipment')
                ->setModule('admin')
                ->setParams(['come_from' => 'shipment'])
                ->forward('view');
            return $resultForward;
        } else {
            return $resultForward->forward('noroute');
        }
    }
}