namespace VendorNameModuleNameBlockAdminhtmlCustomerEdit;

use MagentoCustomerControllerRegistryConstants;
use MagentoUiComponentLayoutTabsTabInterface;
use MagentoBackendBlockWidgetForm;
use MagentoBackendBlockWidgetFormGeneric;
/**
 * Customer account form block
 */
class Tabs extends Generic implements TabInterface
{
    /**
     * @var MagentoStoreModelSystemStore
     */
    protected $_systemStore;
    /**
     * Core registry
     *
     * @var MagentoFrameworkRegistry
     */
    protected $_coreRegistry;

    /**
     * @param MagentoBackendBlockTemplateContext $context
     * @param MagentoFrameworkRegistry $registry
     * @param array $data
     */
    public function __construct(
        MagentoBackendBlockTemplateContext $context,
        MagentoFrameworkRegistry $registry,
        MagentoFrameworkDataFormFactory $formFactory,
        MagentoStoreModelSystemStore $systemStore,

        array $data = []
    ) {
        $this->_coreRegistry = $registry;
        $this->_systemStore = $systemStore;
        parent::__construct($context, $registry, $formFactory, $data);
    }

    /**
     * @return string|null
     */
    public function getCustomerId()
    {
        return $this->_coreRegistry->registry(RegistryConstants::CURRENT_CUSTOMER_ID);
    }

    /**
     * @return MagentoFrameworkPhrase
     */
    public function getTabLabel()
    {
        return __('Demo Tab');
    }

    /**
     * @return MagentoFrameworkPhrase
     */
    public function getTabTitle()
    {
        return __('Demo Tab');
    }

    /**
     * @return bool
     */
    public function canShowTab()
    {
        if ($this->getCustomerId()) {
            return true;
        }
        return false;
    }

    /**
     * @return bool
     */
    public function isHidden()
    {
        if ($this->getCustomerId()) {
            return false;
        }
        return true;
    }

    /**
     * Tab class getter
     *
     * @return string
     */
    public function getTabClass()
    {
        return '';
    }

    /**
     * Return URL link to Tab content
     *
     * @return string
     */
    public function getTabUrl()
    {
        return '';
    }

    /**
     * Tab should be loaded trough Ajax call
     *
     * @return bool
     */
    public function isAjaxLoaded()
    {
        return false;
    }
    public function initForm()
    {
        if (!$this->canShowTab()) {
            return $this;
        }
        /**@var MagentoFrameworkDataForm $form */
        $form = $this->_formFactory->create();
        $form->setHtmlIdPrefix('myform_');

        $fieldset = $form->addFieldset('base_fieldset', ['legend' => __('Fields Information')]);

        $fieldset->addField(
            'demo_field',
            'text',
            [
                'name' => 'demo_field',
                'data-form-part' => $this->getData('target_form'),
                'label' => __('Demo Field in Customer Section'),
                'title' => __('Demo Field in Customer Section')
            ]
        );
        $this->setForm($form);
        return $this;
    }
    /**
     * @return string
     */
    protected function _toHtml()
    {
        if ($this->canShowTab()) {
            $this->initForm();
            return parent::_toHtml();
        } else {
            return '';
        }
    }
}

/** @var MagentoFrameworkAppRequestInterface $request */
$request = $this->getRequest();
$originalRequestData = $request->getPostValue();
echo $originalRequestData['demo_field'];