how to display sub-categories of a parent category

Question

I have this code below that display only 3 of my categories. how can i display sub-category of a parent for example category with an ID of 169;

<?php
namespace Category\Categories\Block\Widget;

class CatewithimgWidget extends \Magento\Framework\View\Element\Template implements \Magento\Widget\Block\BlockInterface
{
    protected $_template = 'widget/categorywidget.phtml';

    /**
     * Default value for products count that will be shown
     */
     protected $_categoryHelper;
     protected $categoryFlatConfig;

     protected $topMenu;
     protected $_categoryFactory;

     protected $mainTitle;
     protected $tagLine;

    /**
     * @param \Magento\Framework\View\Element\Template\Context $context
     * @param \Magento\Catalog\Helper\Category $categoryHelper
     * @param array $data
     */
    public function __construct(
        \Magento\Framework\View\Element\Template\Context $context,
        \Magento\Catalog\Helper\Category $categoryHelper,
        \Magento\Catalog\Model\Indexer\Category\Flat\State $categoryFlatState,
        \Magento\Catalog\Model\CategoryFactory $categoryFactory,
        \Magento\Theme\Block\Html\Topmenu $topMenu
    ) {
        $this->_categoryHelper = $categoryHelper;
        $this->categoryFlatConfig = $categoryFlatState;
        $this->topMenu = $topMenu;
        $this->_categoryFactory = $categoryFactory;
        parent::__construct($context);
    }
    /**
     * Return categories helper
     */
    public function getCategoryHelper()
    {
        return $this->_categoryHelper;
    }

    public function getCategorymodel($id)
    {
         $_category = $this->_categoryFactory->create();
            $_category->load($id);
            return $_category;
    }
    /**
     * Retrieve current store categories
     *
     * @param bool|string $sorted
     * @param bool $asCollection
     * @param bool $toLoad
     * @return \Magento\Framework\Data\Tree\Node\Collection|\Magento\Catalog\Model\Resource\Category\Collection|array
     */

    /**
     * Retrieve collection of selected categories
    */
   public function getCategoryCollection()
    {
        $rootCat = $this->getData('parentcat');


        $category = $this->_categoryFactory->create();
        $collection = $category
                      ->getCollection()
                      ->addAttributeToSelect('image')
                      ->addIdFilter($rootCat);
        return $collection;
    }
    /**
     * Retrieve tag line for widget
    */
    public function getTagLine()
    {
        $tagLine = $this->getData('tagline');
        return $tagLine;
    }
    /**
     * Retrieve main title for widget
    */
    public function getMainTitle()
    {
        $mainTitle = $this->getData('blocktitle');
        return $mainTitle;
    }
}

and phtml file

<?php
    $categories = $this->getCategoryCollection();
    $categoryHelper = $this->getCategoryHelper();
?>
<div class="widget block block-static-block cwiw" id="catewithimg">
    <div class="block-content">
        <div class="content-heading">
            <h2 class="title"><?php echo $this->getMainTitle(); ?></h2>
            <p class="info"><?php echo $this->getTagLine(); ?></p>
        </div>
        <div class="row">
        <?php
        foreach($categories as $category):
            $cat = $this->getCategorymodel($category->getId());
            $image = $cat->getImageUrl();
        ?>
            <?php if($image != null): ?>
                <div class="col-md-4">
                    <a class="category_name" href="<?php echo $cat->getUrl(); ?>">
                       <img src="<?php echo $image; ?>" class="img-responsive category_image" alt="<?php echo $cat->getName(); ?>" />
                        <h3><span><?php echo $cat->getName(); ?></span></h3>
                    </a>
                </div>
            <?php endif; ?>
        <?php endforeach; ?>
        </div>
    </div>
</div>

Answer 1

Try This

app/code/VendoreName/ModuleName/etc

widget.xml

<?xml version="1.0" ?>
<widgets xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:helloworld:Magento_Widget:etc/widget.xsd">
    <widget class="VendoreName\ModuleName\Block\Widget\CategoryList" id="sub_category_list_block">
        <label>Sub-Category Block</label>
        <description>Show sub-category of selected category</description>
        <parameters>
            <parameter name="blocktitle" sort_order="10" visible="true" xsi:type="text">
                <label>Block Title</label>
            </parameter>
            <parameter name="selected_category" xsi:type="select" required="true" source_model="VendoreName\ModuleName\Model\Config\Source\CategoryOptions"
                       visible="true" sort_order="10" >
                <label translate="true">Select Category</label>
            </parameter>
        </parameters>
    </widget>
</widgets>

app/code/VendoreName/ModuleName/Block/Widget

CategoryList.php

<?php

namespace VendoreName\ModuleName\Block\Widget;

use Magento\Framework\View\Element\Template;
use Magento\Widget\Block\BlockInterface;

class CategoryList extends Template implements BlockInterface
{

    // protected $_template = "widget/category_list.phtml";

    protected $_storeManager;
    protected $categoryRepository;

    public function __construct(
        \Magento\Framework\View\Element\Template\Context $context,
        \Magento\Store\Model\StoreManagerInterface $storeManager,
        \Magento\Catalog\Model\CategoryRepository $categoryRepository,
        array $data = []
    ) {
        $this->_storeManager = $storeManager;
        $this->categoryRepository = $categoryRepository;
        parent::__construct($context, $data);
    }

    protected function _construct()
    {
        parent::_construct();
        $this->setTemplate('widget/category_list.phtml');
    }

    public function getChildCategory()
    {
        $catData = $this->getSelectedCategory();
        if ($catData) {
            if ($catData->getChildrenCategories()->count()) {
                return $catData->getChildrenCategories();
            }
        }
        return false;
    }

    public function getSelectedCategory()
    {
        if ($this->getData('selected_category')) {
            return $this->categoryRepository->get(
                $this->getData('selected_category'),
                $this->_storeManager->getStore()->getId()
            );
        }
        return false;
    }

    public function getCategoryData($id)
    {
        return $this->categoryRepository->get(
            $id,
            $this->_storeManager->getStore()->getId()
        );
    }

    public function getCategoryTitle()
    {
        return $this->getData('blocktitle');
    }

}

app/code/VendoreName/ModuleName/Model/Config/Source

CategoryOptions.php

<?php

namespace VendoreName\ModuleName\Model\Config\Source;

use Magento\Framework\Data\OptionSourceInterface;

class CategoryOptions implements OptionSourceInterface
{
    protected $categoryCollectionFactory;

    public function __construct(
        \Magento\Catalog\Model\ResourceModel\Category\CollectionFactory $categoryCollectionFactory
    ) {
        $this->categoryCollectionFactory = $categoryCollectionFactory;
    }

    public function toOptionArray()
    {
        return $this->getCategoryTree();
    }

    protected function getCategoryTree()
    {
        $categoryFactory = $this->categoryCollectionFactory->create();
        $categoryFactory->addAttributeToSelect('*');
        $catOptions = [];
        foreach ($categoryFactory as $category) {
            $catOptions[] = [
                'value' => $category->getId(),
                'label' => $category->getName(),
            ];
        }
        return $catOptions;
    }
}

app/code/VendoreName/ModuleName/view/frontend/templates/widget

category_list.phtml

<?php
$currentCategoryData = $block->getSelectedCategory();
$childCatData = $block->getChildCategory();
?>
<div class="widget block block-static-block cwiw" id="catewithimg">
    <div class="block-content">
        <div class="content-heading">
            <h2 class="title"><?= $block->escapeHtml(__($block->getCategoryTitle())) ?></h2>
        </div>
        <div class="row">
            <?php if($childCatData): ?>
                <?php foreach($childCatData as $category): ?>
                    <div class="col-md-4">
                        <a class="category_name" href="<?= $block->escapeUrl($category->getUrl()) ?>">
                            <h3>
                                <span><?= $block->escapeHtml(__($category->getName())) ?></span>
                            </h3>
                        </a>
                    </div>
                <?php endforeach; ?>
            <?php endif; ?>
        </div>
    </div>
</div>