Magento 2 Fatal Error – Call to a Member Function Create on Null

I got this error while saving image

Fatal error: Call to a member function create() on null in
/opt/lampp/htdocs/magento/2.1/app/code/Contact/Modules/Controller/Contact/Index.php
on line 85

here is my controller

<?php
/**
 *
 * Copyright © 2015 Contactcommerce. All rights reserved.
 */
namespace Contact\Modules\Controller\Contact;

class Index extends \Magento\Framework\App\Action\Action
{

    /**
     * @var \Magento\Framework\App\Cache\TypeListInterface
     */
    protected $_cacheTypeList;

    /**
     * @var \Magento\Framework\App\Cache\StateInterface
     */
    protected $_cacheState;

    /**
     * @var \Magento\Framework\App\Cache\Frontend\Pool
     */
    protected $_cacheFrontendPool;

    /**
     * @var \Magento\Framework\View\Result\PageFactory
     */
    protected $resultPageFactory;
    protected $_objectManager;
    protected $adapterFactory;
    protected $uploader;
    protected $filesystem;

    /**
     * @param Action\Context $context
     * @param \Magento\Framework\App\Cache\TypeListInterface $cacheTypeList
     * @param \Magento\Framework\App\Cache\StateInterface $cacheState
     * @param \Magento\Framework\App\Cache\Frontend\Pool $cacheFrontendPool
     * @param \Magento\Framework\View\Result\PageFactory $resultPageFactory
     */
    public function __construct(
            \Magento\Framework\App\Action\Context $context,
            \Magento\Framework\ObjectManagerInterface $objectManager,
            \Magento\Framework\App\Cache\TypeListInterface $cacheTypeList,
            \Magento\Framework\App\Cache\StateInterface $cacheState,
            \Magento\Framework\App\Cache\Frontend\Pool $cacheFrontendPool,
            \Magento\Framework\View\Result\PageFactory $resultPageFactory,
            \Magento\Framework\Image\AdapterFactory $adapterFactory,
            \Magento\MediaStorage\Model\File\UploaderFactory $uploader,
            \Magento\Framework\Filesystem $filesystem,

            array $data = []
    ) {

        parent::__construct($context, $data);
        $this->_objectManager = $objectManager;
         $this->_cacheTypeList = $cacheTypeList;
        $this->_cacheState = $cacheState;
        $this->_cacheFrontendPool = $cacheFrontendPool;
        $this->resultPageFactory = $resultPageFactory;
    }

    /**
     * Flush cache storage
     *
     */
    public function execute()
    {
        $post = $this->getRequest()->getPostValue();
//        $email = $this->getRequest()->getParam('email');
//        $subject = $this->getRequest()->getParam('subject');
//        $message = $this->getRequest()->getParam('message');
//        $photo = $this->getRequest()->getParam('photo');
        if(isset($post))
        {
        $contact = $this->_objectManager->create('Contact\Modules\Model\Contact');
        $contact->setData('email', $post['email']);
        $contact->setData('subject', $post['subject']);
        $contact->setData('message', $post['message']);
        if (isset($_FILES['photo']) && isset($_FILES['photo']['name']) && strlen($_FILES['photo']['name']))
            {
            $base_media_path = 'Contact/Modules/images';
            $uploader = $this->uploader->create(
                ['fileId' => 'photo']
                );
                $uploader->setAllowedExtensions(['jpg', 'jpeg', 'gif', 'png']);
                $imageAdapter = $this->adapterFactory->create();
                $uploader->addValidateCallback('photo', $imageAdapter, 'validateUploadFile');
                $uploader->setAllowRenameFiles(true);
                $uploader->setFilesDispersion(true);
                $mediaDirectory = $this->filesystem->getDirectoryRead(\Magento\Framework\App\Filesystem\DirectoryList::MEDIA);
                $result = $uploader->save(
                $mediaDirectory->getAbsolutePath(base_media_path));
        }
        $post['photo'] = base_media_path.$result['file'];
        $contact->setData('photo', $post['photo']);
        $contact->save();
        }
        else
        {
        $this->resultPage = $this->resultPageFactory->create();  
    return $this->resultPage;
        }
    }
}

Please suggest me solution of this error..