Magento 2 : Not getting the product grid in a custom form using UI component

Question

I want to show product grid in admin form using UI component, for that, I have added the following code in product_form.xml

 <fieldset name="assign_products">
 <argument name="data" xsi:type="array">
 <item name="config" xsi:type="array">
 <item name="label" xsi:type="string" translate="true">Products</item>
 <item name="collapsible" xsi:type="boolean">true</item>
 <item name="sortOrder" xsi:type="number">40</item>
 </item>
 </argument>
 <container name="assign_products_container" >
 <argument name="data" xsi:type="array">
 <item name="config" xsi:type="array">
 <item name="sortOrder" xsi:type="number">160</item>
 </item>
 </argument>
 <htmlContent name="html_content">
 <argument name="block" xsi:type="object">Company\Module\Block\Adminhtml\Module\AssignProducts</argument>
 </htmlContent>
 </container>
 </fieldset> 

And in AssignProducts.php

<?php
/**
 * Copyright © 2016 Magento. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Company\Module\Block\Adminhtml\Module;
class AssignProducts extends \Magento\Backend\Block\Template
{
 /**
 * Block template
 *
 * @var string
 */
 protected $_template = 'catalog/category/edit/assign_products.phtml';
 /**
 * @var \Magento\Catalog\Block\Adminhtml\Category\Tab\Product
 */
 protected $blockGrid;
 /**
 * @var \Magento\Framework\Registry
 */
 protected $registry;
 /**
 * @var \Magento\Framework\Json\EncoderInterface
 */
 protected $jsonEncoder;
 /**
 * AssignProducts constructor.
 *
 * @param \Magento\Backend\Block\Template\Context $context
 * @param \Magento\Framework\Registry $registry
 * @param \Magento\Framework\Json\EncoderInterface $jsonEncoder
 * @param array $data
 */
 public function __construct(
 \Magento\Backend\Block\Template\Context $context,
 \Magento\Framework\Registry $registry,
 \Magento\Framework\Json\EncoderInterface $jsonEncoder,
 array $data = []
 ) {
 $this->registry = $registry;
 $this->jsonEncoder = $jsonEncoder;
 parent::__construct($context, $data);
 }
 /**
 * Retrieve instance of grid block
 *
 * @return \Magento\Framework\View\Element\BlockInterface
 * @throws \Magento\Framework\Exception\LocalizedException
 */
 public function getBlockGrid()
 {
 if (null === $this->blockGrid) {
 $this->blockGrid = $this->getLayout()->createBlock(
 'Company\Module\Block\Adminhtml\Module\Tab\Product',
 'category.product.grid'
 );
 }
 return $this->blockGrid;
 }
 /**
 * Return HTML of grid block
 *
 * @return string
 */
 public function getGridHtml()
 {
 return $this->getBlockGrid()->toHtml();
 }
 /**
 * @return string
 */
 public function getProductsJson()
 {
 $products = $this->getCategory()->getProductsPosition();
 if (!empty($products)) {
 return $this->jsonEncoder->encode($products);
 }
 return '{}';
 }
 /**
 * Retrieve current category instance
 *
 * @return array|null
 */
 public function getCategory()
 {
 return $this->registry->registry('faqs');
 }
}

In Company\Module\Block\Adminhtml\Module\Tab\Product.php

<?php
namespace Company\Module\Block\Adminhtml\Module\Tab;
use Company\Module\Model\ModuleFactory;
class Product extends \Magento\Backend\Block\Widget\Grid\Extended
{
 /**
 * @var \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory
 */
 protected $productCollectionFactory;
 /**
 * Contact factory
 *
 * @var ContactFactory
 */
 protected $moduleFactory;
 /**
 * @var \Magento\Framework\Registry
 */
 protected $registry;
 protected $_objectManager = null;
 /**
 *
 * @param \Magento\Backend\Block\Template\Context $context
 * @param \Magento\Backend\Helper\Data $backendHelper
 * @param \Magento\Framework\Registry $registry
 * @param ModuleFactory $attachmentFactory
 * @param \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory
 * @param array $data
 */
 public function __construct(
 \Magento\Backend\Block\Template\Context $context,
 \Magento\Backend\Helper\Data $backendHelper,
 \Magento\Framework\Registry $registry,
 \Magento\Framework\ObjectManagerInterface $objectManager,
 ModuleFactory $moduleFactory,
 \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory,
 array $data = []
 ) {
 $this->moduleFactory = $moduleFactory;
 $this->productCollectionFactory = $productCollectionFactory;
 $this->_objectManager = $objectManager;
 $this->registry = $registry;
 parent::__construct($context, $backendHelper, $data);
 }
 /**
 * _construct
 * @return void
 */
 protected function _construct()
 {
 parent::_construct();
 $this->setId('productsGrid');
 $this->setDefaultSort('entity_id');
 $this->setDefaultDir('DESC');
 $this->setSaveParametersInSession(true);
 $this->setUseAjax(true);
 if ($this->getRequest()->getParam('prdt_id')) {
 $this->setDefaultFilter(array('in_product' => 1));
 }
 }
 /**
 * add Column Filter To Collection
 */
 protected function _addColumnFilterToCollection($column)
 {
 // Set custom filter for in category flag
 if ($column->getId() == 'in_product') {
 $productIds = $this->_getSelectedProducts();
 if (empty($productIds)) {
 $productIds = 0;
 }
 if ($column->getFilter()->getValue()) {
 $this->getCollection()->addFieldToFilter('entity_id', ['in' => $productIds]);
 } elseif (!empty($productIds)) {
 $this->getCollection()->addFieldToFilter('entity_id', ['nin' => $productIds]);
 }
 } else {
 parent::_addColumnFilterToCollection($column);
 }
 return $this;
 }
 /**
 * prepare collection
 */
 protected function _prepareCollection()
 {
 $collection = $this->productCollectionFactory->create();
 $collection->addAttributeToSelect('name');
 $collection->addAttributeToSelect('sku');
 $collection->addAttributeToSelect('price');
 $this->setCollection($collection);
 return parent::_prepareCollection();
 }
 /**
 * @return $this
 */
 protected function _prepareColumns()
 {
 /* @var $model \Webspeaks\ProductsGrid\Model\Slide */
 $model = $this->_objectManager->get('\Company\Module\Model\Module');
 $this->addColumn(
 'in_product',
 [
 'header_css_class' => 'a-center',
 'type' => 'checkbox',
 'name' => 'in_product',
 'align' => 'center',
 'index' => 'entity_id',
 'values' => $this->_getSelectedProducts(),
 ]
 );
 $this->addColumn(
 'entity_id',
 [
 'header' => __('Product ID'),
 'type' => 'number',
 'index' => 'entity_id',
 'header_css_class' => 'col-id',
 'column_css_class' => 'col-id',
 ]
 );
 $this->addColumn(
 'name',
 [
 'header' => __('Name'),
 'index' => 'name',
 'class' => 'xxx',
 'width' => '50px',
 ]
 );
 $this->addColumn(
 'sku',
 [
 'header' => __('Sku'),
 'index' => 'sku',
 'class' => 'xxx',
 'width' => '50px',
 ]
 );
 $this->addColumn(
 'price',
 [
 'header' => __('Price'),
 'type' => 'currency',
 'index' => 'price',
 'width' => '50px',
 ]
 );
 return parent::_prepareColumns();
 }
 /**
 * @return string
 */
 public function getGridUrl()
 {
 return $this->getUrl('*/*/productsgrid', ['_current' => true]);
 }
 /**
 * @param object $row
 * @return string
 */
 public function getRowUrl($row)
 {
 return '';
 }
 protected function _getSelectedProducts()
 {
 $product = $this->getPrdt();
 return $product->getProducts($product);
 }
 /**
 * Retrieve selected products
 *
 * @return array
 */
 public function getSelectedProducts()
 {
 $product = $this->getPrdt();
 $selected = $product->getProducts($product);
 if (!is_array($selected)) {
 $selected = [];
 }
 return $selected;
 }
 protected function getPrdt()
 {
 $prdtId = $this->getRequest()->getParam('prdt_id');
 $product = $this->moduleFactory->create();
 if ($prdtId) {
 $product->load($prdtId);
 }
 return $product;
 }
 /**
 * {@inheritdoc}
 */
 public function canShowTab()
 {
 return true;
 }
 /**
 * {@inheritdoc}
 */
 public function isHidden()
 {
 return true;
 }
}

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