Add Products through Custom module in magento2

Question

I'm trying to add number of products to cart at a time using custom module

here is my module code

app/code/Multiple/Addtocart/Controller/Index/Cartadd.php

<?php
    namespace Multiple\Addtocart\Controller\Index;    
    use Magento\Framework\Controller\ResultFactory;
    use Magento\Framework\App\Action\Action;
    use Magento\Framework\App\Action\Context;
    use Magento\Framework\View\Result\PageFactory;
    use Magento\Checkout\Model\Cart as CustomerCart;
class Cartadd extends \Magento\Framework\App\Action\Action
{
    protected $resultPageFactory;
    protected $checkoutSession;
    protected $formKey;
    protected $request;
    protected $cart;

  public function __construct(
    Context $context,
    \Magento\Framework\Data\Form\FormKey $formKey,
    \Magento\Checkout\Model\Session $checkoutSession,
     CustomerCart $cart,
    PageFactory $resultPageFactory,
    array $data = []) 
    { 
        $this->formKey = $formKey;
        $this->resultPageFactory = $resultPageFactory;
         $this->checkoutSession = $checkoutSession;
        $this->cart = $cart;
        parent::__construct($context);
    }


  public function execute()
  {
    $pid=array();
    $pid=$_POST['data'];
    $objectManager = \Magento\Framework\App\ObjectManager::getInstance();
    for($i=0;$i<count($pid);$i++){
        $product_id=$pid[$i]['id'];
        $product_qty=$pid[$i]['qty'];
        $_product = $objectManager->create('Magento\Catalog\Model\Product')->load($product_id);
        echo $_product->getName()."<br>";
        $params = array(
                    'form_key' => $this->formKey->getFormKey(),
                    'product' =>$product_id, //product Id
                    'qty'   =>$product_qty //quantity of product                
                    );              

                  //$_product = $this->product->load($tradeProductId);
                  //$this->cart->truncate();
                  $this->cart->addProduct($_product, $params);
                  $this->cart->save();
                  $this->messageManager->addSuccess(__('Item has been successfully added to cart.'));   
    }   

  }
}

app/code/Multiple/Addtocart/etc/frontend/events.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="add_prodct_addtocart_after">
        <observer name="Multiple_Addtocart" instance="Multiple\Addtocart\Observer\CustomPrice" />
    </event>
</config>

app/code/Multiple/Addtocart/Observer/CustomPrice.php

<?php
    namespace Multiple\Addtocart\Observer;
    use Magento\Framework\Event\ObserverInterface;
    use Magento\Framework\App\RequestInterface;
    use Psr\Log\LoggerInterface;
    class CustomPrice implements ObserverInterface
    {

    public function execute(\Magento\Framework\Event\Observer $observer) 
    {
            $writer = new \Zend\Log\Writer\Stream(BP.'/var/log/multiproduct.log');
            $logger = new \Zend\Log\Logger();
            $logger->addWriter($writer);
}
}

Answer 1

Step 1:- Template File path:- /app/code/Multiple/Addtocart/view/frontend/templates/addtocart_index_index.phtml

<form name="paytrade-orders-list" id="paytrade-orders-list" action="<?php echo $this->getUrl('addtocart/index/cartadd');?>" method="post" >

<div class="saveandmore">
<button type="submit" class="buyersave"><?php echo _('Pay Now');?></button>
<label><span><?php echo _('Select all');?> </span><input type="checkbox" id="select_all" /></label>
</div>

</form>

Step2:-

/app/code/Multiple/Addtocart/Controller/Index/Cartadd.php

<?php
    namespace Multiple\Addtocart\Controller\Index;    
    use Magento\Framework\Controller\ResultFactory;
    use Magento\Framework\App\Action\Action;
    use Magento\Framework\App\Action\Context;
    use Magento\Framework\View\Result\PageFactory;
class Cartadd extends \Magento\Framework\App\Action\Action
{
    protected $resultPageFactory;
    protected $formKey;
    protected $request;

  public function __construct(
    Context $context,
    \Magento\Framework\Data\Form\FormKey $formKey,
    PageFactory $resultPageFactory,
    array $data = []) 
    { 
        $this->formKey = $formKey;
        $this->resultPageFactory = $resultPageFactory;
        parent::__construct($context);
    }


  public function execute()
  {
    echo 'Hello World';   

  }
}

Step 3:- Use di compile and clear cache and full page cache when ever u change the __construct()

as well as use magento2 log whether u r controller is calling or not