Magento 2.2.0 - __construct() must be an instance of Magento\Framework\View\Result\PageFactory,

Question

Controller File

<?php

namespace Magento2\HelloWorld\Controller\Index;

use \Magento\Framework\App\Action\Action;
use \Magento\Framework\View\Result\PageFactory;
use \Magento\Framework\View\Result\Page;
use \Magento\Framework\App\Action\Context;
use \Magento\Framework\Exception\LocalizedException;


class Index extends Action
{

    /**
     * @var PageFactory
     */
    protected $resultPageFactory;

    /**
     * @param Context $context
     * @param PageFactory $resultPageFactory
     *
     * @codeCoverageIgnore
     * @SuppressWarnings(PHPMD.ExcessiveParameterList)
     */
    public function __construct(
        Context $context,
        PageFactory $resultPageFactory
    ) {
        parent::__construct(
            $context
        );
        $this->resultPageFactory = $resultPageFactory;
    }

    public function execute()
    {

        $resultPage = $this->resultPageFactory->create();
        return $resultPage;
    }
}

It throws below exception while trying to run controller, while I have already mentioned use \Magento\Framework\View\Result\PageFactory;

Fatal error: Uncaught TypeError: Argument 2 passed to Magento2\HelloWorld\Controller\Index\Index::__construct() must be an instance of Magento\Framework\View\Result\PageFactory

If I simply use below, it works

<?php

namespace Magento2\HelloWorld\Controller\Index;

use \Magento\Framework\App\Action\Action;
use \Magento\Framework\View\Result\PageFactory;
use \Magento\Framework\View\Result\Page;
use \Magento\Framework\App\Action\Context;
use \Magento\Framework\Exception\LocalizedException;


class Index extends Action
{

    public function execute()
    {

        $this->_view->loadLayout();
        $this->_view->getLayout()->initMessages();
        $this->_view->renderLayout();
    }

}

How can I resolve the __construct() error ?

Answer 1

Change __construct function to

public function __construct(
    Context $context,
    PageFactory $resultPageFactory
) {

    $this->resultPageFactory = $resultPageFactory;
    parent::__construct(
        $context
    );
}

and Change

class Index extends \Magento\Framework\App\Action\Action

from

class Index extends Action

Also remove

use \Magento\Framework\App\Action\Action;

Answer 2

Your code is correct there is no any issue.

Follow below step

1) remove cache: php bin/magento cache:flush

2) remove var/generation : rm -rf var/generation