How to display newly added widget for a particular category

Question

I have replicated Catalog New Products List in magento and added a category chooser field to it. How to filter new products using category id? app/code/[vendor]/Newproducts/Block/Product/Widget/NewWidget.php

  /**
    * New products widget
    */
 class NewWidget extends \Magento\Catalog\Block\Product\NewProduct implements \Magento\Widget\Block\BlockInterface
  {
    /**
 * Display products type - all products
 */
const DISPLAY_TYPE_ALL_PRODUCTS = 'all_products';

/**
 * Display products type - new products
 */
const DISPLAY_TYPE_NEW_PRODUCTS = 'new_products';

/**
 * Default value whether show pager or not
 */
const DEFAULT_SHOW_PAGER = false;

/**
 * Default value for products per page
 */
const DEFAULT_PRODUCTS_PER_PAGE = 5;

/**
 * Name of request parameter for page number value
 *
 * @deprecated
 */
const PAGE_VAR_NAME = 'np';

/**
 * Instance of pager block
 *
 * @var \Magento\Catalog\Block\Product\Widget\Html\Pager
 */
protected $_pager;

/**
 * @var \Magento\Framework\Serialize\Serializer\Json
 */
private $serializer;

/**
 * NewWidget constructor.
 *
 * @param \Magento\Catalog\Block\Product\Context $context
 * @param \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory
 * @param \Magento\Catalog\Model\Product\Visibility $catalogProductVisibility
 * @param \Magento\Framework\App\Http\Context $httpContext
 * @param array $data
 * @param \Magento\Framework\Serialize\Serializer\Json|null $serializer
 */
public function __construct(
    \Magento\Catalog\Block\Product\Context $context,
    \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory,
    \Magento\Catalog\Model\Product\Visibility $catalogProductVisibility,
    \Magento\Framework\App\Http\Context $httpContext,
    array $data = [],
    \Magento\Framework\Serialize\Serializer\Json $serializer = null
) {
    parent::__construct(
        $context,
        $productCollectionFactory,
        $catalogProductVisibility,
        $httpContext,
        $data
    );
    $this->serializer = $serializer ?: \Magento\Framework\App\ObjectManager::getInstance()
        ->get(\Magento\Framework\Serialize\Serializer\Json::class);
}

/**
 * Product collection initialize process
 *
 * @return \Magento\Catalog\Model\ResourceModel\Product\Collection|Object|\Magento\Framework\Data\Collection
 */
protected function _getProductCollection()
{
    switch ($this->getDisplayType()) {
        case self::DISPLAY_TYPE_NEW_PRODUCTS:
                $collection = parent::_getProductCollection()
                ->setPageSize($this->getPageSize())
                ->setCurPage($this->getCurrentPage());
            break;
        default:
            $collection = $this->_getRecentlyAddedProductsCollection();
            break;
    }
    return $collection;
}

/**
 * Prepare collection for recent product list
 *
 * @return \Magento\Catalog\Model\ResourceModel\Product\Collection|Object|\Magento\Framework\Data\Collection
 */
protected function _getRecentlyAddedProductsCollection()
{
    /** @var $collection \Magento\Catalog\Model\ResourceModel\Product\Collection */
      $rootCat = $this->getData('parentcat');
    $collection = $this->_productCollectionFactory->create();
    $collection->setVisibility($this->_catalogProductVisibility->getVisibleInCatalogIds());
        $collection = $this->_addProductAttributesAndPrices($collection)
        ->addIdFilter($rootCat)
        ->addStoreFilter()
        ->addAttributeToSort('created_at', 'desc')
        ->setPageSize($this->getPageSize())
        ->setCurPage($this->getCurrentPage());
    return $collection;
}

/**
 * Get number of current page based on query value
 *
 * @return int
 */
public function getCurrentPage()
{
    return abs((int)$this->getRequest()->getParam($this->getData('page_var_name')));
}

/**
 * Get key pieces for caching block content
 *
 * @return array
 */
public function getCacheKeyInfo()
{
    return array_merge(
        parent::getCacheKeyInfo(),
        [
            $this->getDisplayType(),
            $this->getProductsPerPage(),
            intval($this->getRequest()->getParam($this->getData('page_var_name'), 1)),
            $this->serializer->serialize($this->getRequest()->getParams())
        ]
    );
}

/**
 * Retrieve display type for products
 *
 * @return string
 */
public function getDisplayType()
{
    if (!$this->hasData('display_type')) {
        $this->setData('display_type', self::DISPLAY_TYPE_ALL_PRODUCTS);
    }
    return $this->getData('display_type');
}
/**
 * Retrieve category id
 *
 * @return product collection
 */
public function getCategoryId()
{
  $rootCat = $this->getData('parentcat');


    $category = $this->_categoryFactory->create();
    $collection = $category
                  ->getCollection()
                  ->addIdFilter($rootCat);
    return $collection;
}
/**
 * Retrieve block type
 *
 * @return string
 */
public function getMainTitle()
{
  $mainTitle = $this->getData('blocktitle');
  return $mainTitle;
}

/**
 * Retrieve how many products should be displayed
 *
 * @return int
 */
public function getProductsCount()
{
    if (!$this->hasData('products_count')) {
        return parent::getProductsCount();
    }
    return $this->getData('products_count');
}

/**
 * Retrieve how many products should be displayed
 *
 * @return int
 */
public function getProductsPerPage()
{
    if (!$this->hasData('products_per_page')) {
        $this->setData('products_per_page', self::DEFAULT_PRODUCTS_PER_PAGE);
    }
    return $this->getData('products_per_page');
}

/**
 * Return flag whether pager need to be shown or not
 *
 * @return bool
 */
public function showPager()
{
    if (!$this->hasData('show_pager')) {
        $this->setData('show_pager', self::DEFAULT_SHOW_PAGER);
    }
    return (bool)$this->getData('show_pager');
}

/**
 * Retrieve how many products should be displayed on page
 *
 * @return int
 */
protected function getPageSize()
{
    return $this->showPager() ? $this->getProductsPerPage() : $this->getProductsCount();
}

/**
 * Render pagination HTML
 *
 * @return string
 */
public function getPagerHtml()
{
    if ($this->showPager()) {
        if (!$this->_pager) {
            $this->_pager = $this->getLayout()->createBlock(
                \Magento\Catalog\Block\Product\Widget\Html\Pager::class,
                'widget.new.product.list.pager'
            );

            $this->_pager->setUseContainer(true)
                ->setShowAmounts(true)
                ->setShowPerPage(false)
                ->setPageVarName($this->getData('page_var_name'))
                ->setLimit($this->getProductsPerPage())
                ->setTotalLimit($this->getProductsCount())
                ->setCollection($this->getProductCollection());
        }
        if ($this->_pager instanceof \Magento\Framework\View\Element\AbstractBlock) {
            return $this->_pager->toHtml();
        }
    }
    return '';
}

/**
 * Return HTML block with price
 *
 * @param \Magento\Catalog\Model\Product $product
 * @param string $priceType
 * @param string $renderZone
 * @param array $arguments
 * @return string
 * @SuppressWarnings(PHPMD.NPathComplexity)
 */
public function getProductPriceHtml(
    \Magento\Catalog\Model\Product $product,
    $priceType = null,
    $renderZone = \Magento\Framework\Pricing\Render::ZONE_ITEM_LIST,
    array $arguments = []
) {
    if (!isset($arguments['zone'])) {
        $arguments['zone'] = $renderZone;
    }
    $arguments['zone'] = isset($arguments['zone'])
        ? $arguments['zone']
        : $renderZone;
    $arguments['price_id'] = isset($arguments['price_id'])
        ? $arguments['price_id']
        : 'old-price-' . $product->getId() . '-' . $priceType;
    $arguments['include_container'] = isset($arguments['include_container'])
        ? $arguments['include_container']
        : true;
    $arguments['display_minimal_price'] = isset($arguments['display_minimal_price'])
        ? $arguments['display_minimal_price']
        : true;

        /** @var \Magento\Framework\Pricing\Render $priceRender */
    $priceRender = $this->getLayout()->getBlock('product.price.render.default');

    $price = '';
    if ($priceRender) {
        $price = $priceRender->render(
            \Magento\Catalog\Pricing\Price\FinalPrice::PRICE_CODE,
            $product,
            $arguments
        );
    }
    return $price;
}
}

Answer 1

Update your class with below code:

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Dyode\Newproducts\Block\Product\Widget;

/**
 * New products widget
 */
class NewWidget extends \Magento\Catalog\Block\Product\NewProduct implements \Magento\Widget\Block\BlockInterface
{
    /**
     * Display products type - all products
     */
    const DISPLAY_TYPE_ALL_PRODUCTS = 'all_products';

    /**
     * Display products type - new products
     */
    const DISPLAY_TYPE_NEW_PRODUCTS = 'new_products';

    /**
     * Default value whether show pager or not
     */
    const DEFAULT_SHOW_PAGER = false;

    /**
     * Default value for products per page
     */
    const DEFAULT_PRODUCTS_PER_PAGE = 5;

    /**
     * Name of request parameter for page number value
     *
     * @deprecated
     */
    const PAGE_VAR_NAME = 'np';

    /**
     * Instance of pager block
     *
     * @var \Magento\Catalog\Block\Product\Widget\Html\Pager
     */
    protected $_pager;

    /**
     * @var \Magento\Framework\Serialize\Serializer\Json
     */
    private $serializer;

    /**
     * NewWidget constructor.
     *
     * @param \Magento\Catalog\Block\Product\Context $context
     * @param \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory
     * @param \Magento\Catalog\Model\Product\Visibility $catalogProductVisibility
     * @param \Magento\Framework\App\Http\Context $httpContext
     * @param array $data
     * @param \Magento\Framework\Serialize\Serializer\Json|null $serializer
     */
    public function __construct(
        \Magento\Catalog\Block\Product\Context $context,
        \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory,
        \Magento\Catalog\Model\Product\Visibility $catalogProductVisibility,
        \Magento\Framework\App\Http\Context $httpContext,
        array $data = [],
        \Magento\Framework\Serialize\Serializer\Json $serializer = null
    ) {
        parent::__construct(
            $context,
            $productCollectionFactory,
            $catalogProductVisibility,
            $httpContext,
            $data
        );
        $this->serializer = $serializer ?: \Magento\Framework\App\ObjectManager::getInstance()
            ->get(\Magento\Framework\Serialize\Serializer\Json::class);
    }

    /**
     * Product collection initialize process
     *
     * @return \Magento\Catalog\Model\ResourceModel\Product\Collection|Object|\Magento\Framework\Data\Collection
     */
    protected function _getProductCollection()
    {
        switch ($this->getDisplayType()) {
            case self::DISPLAY_TYPE_NEW_PRODUCTS:
                $filterCats = explode(',',$this->getData('parentcat'));
                $collection = parent::_getProductCollection()
                    ->addCategoriesFilter(array('in' => $filterCats))
                    ->setPageSize($this->getPageSize())
                    ->setCurPage($this->getCurrentPage());
                break;
            default:
                $collection = $this->_getRecentlyAddedProductsCollection();
                break;
        }
        return $collection;
    }

    /**
     * Prepare collection for recent product list
     *
     * @return \Magento\Catalog\Model\ResourceModel\Product\Collection|Object|\Magento\Framework\Data\Collection
     */
    protected function _getRecentlyAddedProductsCollection()
    {
        /** @var $collection \Magento\Catalog\Model\ResourceModel\Product\Collection */
        $collection = $this->_productCollectionFactory->create();
        $collection->setVisibility($this->_catalogProductVisibility->getVisibleInCatalogIds());

        $filterCats = explode(',',$this->getData('parentcat'));

        $collection = $this->_addProductAttributesAndPrices($collection)
            ->addCategoriesFilter(array('in' => $filterCats))
            ->addStoreFilter()
            ->addAttributeToSort('created_at', 'desc')
            ->setPageSize($this->getPageSize())
            ->setCurPage($this->getCurrentPage());
        return $collection;
    }

    /**
     * Get number of current page based on query value
     *
     * @return int
     */
    public function getCurrentPage()
    {
        return abs((int)$this->getRequest()->getParam($this->getData('page_var_name')));
    }

    /**
     * Get key pieces for caching block content
     *
     * @return array
     */
    public function getCacheKeyInfo()
    {
        return array_merge(
            parent::getCacheKeyInfo(),
            [
                $this->getDisplayType(),
                $this->getProductsPerPage(),
                intval($this->getRequest()->getParam($this->getData('page_var_name'), 1)),
                $this->serializer->serialize($this->getRequest()->getParams())
            ]
        );
    }

    /**
     * Retrieve display type for products
     *
     * @return string
     */
    public function getDisplayType()
    {
        if (!$this->hasData('display_type')) {
            $this->setData('display_type', self::DISPLAY_TYPE_ALL_PRODUCTS);
        }
        return $this->getData('display_type');
    }
    /**
     * Retrieve category id
     *
     * @return product collection
     */
    public function getCategoryId()
    {
      $rootCat = $this->getData('parentcat');


        // $category = $this->_categoryFactory->create();
        // $collection = $category
        //               ->getCollection()
        //               ->addIdFilter($rootCat);
        // return $collection;
    }
    /**
     * Retrieve block type
     *
     * @return string
     */
    public function getMainTitle()
    {
      $mainTitle = $this->getData('blocktitle');
      return $mainTitle;
    }

    /**
     * Retrieve how many products should be displayed
     *
     * @return int
     */
    public function getProductsCount()
    {
        if (!$this->hasData('products_count')) {
            return parent::getProductsCount();
        }
        return $this->getData('products_count');
    }

    /**
     * Retrieve how many products should be displayed
     *
     * @return int
     */
    public function getProductsPerPage()
    {
        if (!$this->hasData('products_per_page')) {
            $this->setData('products_per_page', self::DEFAULT_PRODUCTS_PER_PAGE);
        }
        return $this->getData('products_per_page');
    }

    /**
     * Return flag whether pager need to be shown or not
     *
     * @return bool
     */
    public function showPager()
    {
        if (!$this->hasData('show_pager')) {
            $this->setData('show_pager', self::DEFAULT_SHOW_PAGER);
        }
        return (bool)$this->getData('show_pager');
    }

    /**
     * Retrieve how many products should be displayed on page
     *
     * @return int
     */
    protected function getPageSize()
    {
        return $this->showPager() ? $this->getProductsPerPage() : $this->getProductsCount();
    }

    /**
     * Render pagination HTML
     *
     * @return string
     */
    public function getPagerHtml()
    {
        if ($this->showPager()) {
            if (!$this->_pager) {
                $this->_pager = $this->getLayout()->createBlock(
                    \Magento\Catalog\Block\Product\Widget\Html\Pager::class,
                    'widget.new.product.list.pager'
                );

                $this->_pager->setUseContainer(true)
                    ->setShowAmounts(true)
                    ->setShowPerPage(false)
                    ->setPageVarName($this->getData('page_var_name'))
                    ->setLimit($this->getProductsPerPage())
                    ->setTotalLimit($this->getProductsCount())
                    ->setCollection($this->getProductCollection());
            }
            if ($this->_pager instanceof \Magento\Framework\View\Element\AbstractBlock) {
                return $this->_pager->toHtml();
            }
        }
        return '';
    }

    /**
     * Return HTML block with price
     *
     * @param \Magento\Catalog\Model\Product $product
     * @param string $priceType
     * @param string $renderZone
     * @param array $arguments
     * @return string
     * @SuppressWarnings(PHPMD.NPathComplexity)
     */
    public function getProductPriceHtml(
        \Magento\Catalog\Model\Product $product,
        $priceType = null,
        $renderZone = \Magento\Framework\Pricing\Render::ZONE_ITEM_LIST,
        array $arguments = []
    ) {
        if (!isset($arguments['zone'])) {
            $arguments['zone'] = $renderZone;
        }
        $arguments['zone'] = isset($arguments['zone'])
            ? $arguments['zone']
            : $renderZone;
        $arguments['price_id'] = isset($arguments['price_id'])
            ? $arguments['price_id']
            : 'old-price-' . $product->getId() . '-' . $priceType;
        $arguments['include_container'] = isset($arguments['include_container'])
            ? $arguments['include_container']
            : true;
        $arguments['display_minimal_price'] = isset($arguments['display_minimal_price'])
            ? $arguments['display_minimal_price']
            : true;

            /** @var \Magento\Framework\Pricing\Render $priceRender */
        $priceRender = $this->getLayout()->getBlock('product.price.render.default');

        $price = '';
        if ($priceRender) {
            $price = $priceRender->render(
                \Magento\Catalog\Pricing\Price\FinalPrice::PRICE_CODE,
                $product,
                $arguments
            );
        }
        return $price;
    }
}