Magento 2: How to redirect to checkout page after product added to cart via Observer/Plugin from category page?

Question

I have followed below & it works fine

Magento 2 : Add to Cart Button redirect to contact page

Only issue it should be redirected after product is added to cart.

I have tried different methods but seems not working http://devdocs.magento.com/guides/v2.0/extension-dev-guide/plugins.html

I tried using Observer but unable to redirect from Observer because of AJAX. It it's not AJAX then it works fine.

If somebody can guide how to redirect from Checkout page after product is added to cart. It would be better.

I'm using Porto Theme. So don't want to remove AJAX feature while Add to Cart

[UPDATE]

Through plugin I have achieved. Need to achieve something using Observer

public function afterExecute(\Magento\Checkout\Controller\Cart\Add $subject, $result) {
    $result = [];
    $result['backUrl'] = $this->url->getUrl('checkout');
    $subject->getResponse()->representJson($this->objectManager->get('Magento\Framework\Json\Helper\Data')->jsonEncode($result));
    return;
}

Answer 1

try this code.

use Magento\Framework\Event\ObserverInterface;

class TestObserver implements ObserverInterface
{
    protected $_responseFactory;
    protected $_url;

    public function __construct(\Magento\Framework\App\ResponseFactory $responseFactory,
\Magento\Framework\UrlInterface $url)
    {
        $this->_responseFactory = $responseFactory;
        $this->_url = $url;
    }

    public function execute(\Magento\Framework\Event\Observer $observer)
    {
        $cartUrl = $this->_url->getUrl('checkout/cart/index');
        $this->_responseFactory->create()->setRedirect($cartUrl)->sendResponse();            
        exit;
    }
}