Enable disabled functionality is not working in magento 2

Question

I am trying to enable/disable Magento 2 from admin general setting. I created an option to disabled / enabled module from backend > configuration > module > enable (Yes/No)

when I tried to disabled module functionality still working. Is it a database related issue or another issue.

Secondly, I tried to get check in coding whether module enable or not by followed below steps

Index controller :-

<?php  
namespace Vender\Modulename\Controller\Index;
use Magento\Framework\App\Action\Context;

class Index extends \Magento\Framework\App\Action\Action 
   {
      protected $resultJsonFactory;
      protected $scopeConfig;

      public function __construct(Context $context, 
      \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig,
     \Magento\Framework\Controller\Result\JsonFactory $resultJsonFactory)
        {
           $this->resultJsonFactory  = $resultJsonFactory;
         //$this->_helper = $helper;
           $this->scopeConfig = $scopeConfig;
           parent::__construct($context);
        }
      protected function helper($className) 
      {
         return $this->_objectManager->get($className);
       }

      protected function getUrl($path) 
     {
      return $this->_objectManager->get('Magento\Framework\UrlInterface')->getUrl($path);
      }

     public function execute()
     {
    //die('dfsd');
    //$topTel = $this->_helper->getConfig('dynamicpdf/general/topTel');
    //$_thishepler = $this->_helper('Vender\Modulename\Helper\Data');
    //$isEnabled = $helper->getStoreConfig('VenderMOdulename/general/enabled');
    //print_r($isEnabled); die;
    $helper = \Magento\Framework\App\ObjectManager::getInstance()->get('Vendor\modulename\Helper\Data');

    echo "<pre>";
    //print_r($helper);

    if($helper->isEnable()){
    }
          // My code
  }

}

Helper > Data.php

namespace Vendor\Modulename\Helper;
use Magento\Framework\App\Helper\AbstractHelper;
use Magento\Framework\App\Helper\Context;
use Magento\Store\Model\ScopeInterface;

class Data extends AbstractHelper
{
   protected $context;

   public function __construct(Context $context)
   {
       $this->context = $context;
       parent::__construct($context);
   }

   public function isEnable()
   {
    return $this->scopeConfig->getValue('modulename/general/enable', ScopeInterface::SCOPE_STORE);
   }
}

Answer 1

If you enabled/disabled one or more modules, then you will need to run magento setup:upgrade to update the database schema.

Try running commands:

php bin/magento setup:upgrade
php bin/magento c:c

Answer 2

Use below code in your Index Controller file.

protected $helperData;

public function __construct(
    \Vendor\Modulename\Helper\Data $helperData
) {
    $this->helperData = $helperData;
}

then use below code to call your helper function.

$this->helperData->isEnable();

EDIT: in your helper file you didn't declare variable

protected $scopeConfig;

public function __construct(
    \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig
)
{
    $this->scopeConfig = $scopeConfig;
}

This is the proper way to call helper function/method instead using Object Manager.

Don't forget to flush cache.