VoidAction.php

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

use Magento\Backend\App\Action;

class VoidAction extends Action
{
    /**
     * Authorization level of a basic admin session
     *
     * @see _isAllowed()
     */
    const ADMIN_RESOURCE = 'Magento_Sales::sales_creditmemo';

    /**
     * @var \Magento\Sales\Controller\Adminhtml\Order\CreditmemoLoader
     */
    protected $creditmemoLoader;

    /**
     * @var \Magento\Backend\Model\View\Result\ForwardFactory
     */
    protected $resultForwardFactory;

    /**
     * @param Action\Context $context
     * @param \Magento\Sales\Controller\Adminhtml\Order\CreditmemoLoader $creditmemoLoader
     * @param \Magento\Backend\Model\View\Result\ForwardFactory $resultForwardFactory
     */
    public function __construct(
        Action\Context $context,
        \Magento\Sales\Controller\Adminhtml\Order\CreditmemoLoader $creditmemoLoader,
        \Magento\Backend\Model\View\Result\ForwardFactory $resultForwardFactory
    ) {
        $this->creditmemoLoader = $creditmemoLoader;
        $this->resultForwardFactory = $resultForwardFactory;
        parent::__construct($context);
    }

    /**
     * Void creditmemo action
     *
     * @return \Magento\Backend\Model\View\Result\Redirect|\Magento\Backend\Model\View\Result\Forward
     */
    public function execute()
    {
        $this->creditmemoLoader->setOrderId($this->getRequest()->getParam('order_id'));
        $this->creditmemoLoader->setCreditmemoId($this->getRequest()->getParam('creditmemo_id'));
        $this->creditmemoLoader->setCreditmemo($this->getRequest()->getParam('creditmemo'));
        $this->creditmemoLoader->setInvoiceId($this->getRequest()->getParam('invoice_id'));
        $creditmemo = $this->creditmemoLoader->load();
        if ($creditmemo) {
            try {
                $creditmemo->void();
                $transactionSave = $this->_objectManager->create(\Magento\Framework\DB\Transaction::class);
                $transactionSave->addObject($creditmemo);
                $transactionSave->addObject($creditmemo->getOrder());

                if ($creditmemo->getInvoice()) {
                    $transactionSave->addObject($creditmemo->getInvoice());
                }
                $transactionSave->save();
                $this->messageManager->addSuccessMessage(__('You voided the credit memo.'));
            } catch (\Magento\Framework\Exception\LocalizedException $e) {
                $this->messageManager->addErrorMessage($e->getMessage());
            } catch (\Exception $e) {
                $this->messageManager->addErrorMessage(__('We can\'t void the credit memo.'));
            }
            $resultRedirect = $this->resultRedirectFactory->create();
            $resultRedirect->setPath('sales/*/view', ['creditmemo_id' => $creditmemo->getId()]);
            return $resultRedirect;
        } else {
            $resultForward = $this->resultForwardFactory->create();
            $resultForward->forward('noroute');
            return $resultForward;
        }
    }
}