After Successful Installation Magento Getting Blank Gray page for Admin

[gregopante3d50]

Worked for me as well.

I had a similar error after successful installation with cmd line.

My error was:

Spoiler

1 exception(s): Exception #0 (Exception): Warning: Use of undefined constant fileDriver - assumed 'fileDriver' (this will throw an Error in a future version of PHP)  [....] Validator.php on line 139

[sathyakuma37b7]

1 exception(s):
Exception #0 (Exception): Warning: Undefined variable $Path in C:\xampp\htdocs\mage2rock\vendor\magento\framework\View\Element\Template\File\Validator.php on line 140

Exception #0 (Exception): Warning: Undefined variable $Path in C:\xampp\htdocs\mage2rock\vendor\magento\framework\View\Element\Template\File\Validator.php on line 140
<pre>#1 Magento\Framework\View\Element\Template\File\Validator->isPathInDirectories() called at [vendor\magento\framework\View\Element\Template\File\Validator.php:117]
#2 Magento\Framework\View\Element\Template\File\Validator->isValid() called at [vendor\magento\framework\View\Element\Template.php:260]
#3 Magento\Framework\View\Element\Template->fetchView() called at [vendor\magento\framework\View\Element\Template.php:293]
#4 Magento\Framework\View\Element\Template->_toHtml() called at [vendor\magento\framework\View\Element\AbstractBlock.php:1095]
#5 Magento\Framework\View\Element\AbstractBlock->Magento\Framework\View\Element\{closure}() called at [vendor\magento\framework\View\Element\AbstractBlock.php:1099]
#6 Magento\Framework\View\Element\AbstractBlock->_loadCache() called at [vendor\magento\framework\View\Element\AbstractBlock.php:660]
#7 Magento\Framework\View\Element\AbstractBlock->toHtml() called at [vendor\magento\framework\View\Result\Page.php:251]
#8 Magento\Framework\View\Result\Page->render() called at [vendor\magento\framework\View\Result\Layout.php:171]
#9 Magento\Framework\View\Result\Layout->renderResult() called at [vendor\magento\framework\Interception\Interceptor.php:58]
#10 Magento\Framework\View\Result\Page\Interceptor->___callParent() called at [vendor\magento\framework\Interception\Interceptor.php:138]
#11 Magento\Framework\View\Result\Page\Interceptor->Magento\Framework\Interception\{closure}() called at [vendor\magento\framework\Interception\Interceptor.php:153]
#12 Magento\Framework\View\Result\Page\Interceptor->___callPlugins() called at [generated\code\Magento\Framework\View\Result\Page\Interceptor.php:95]
#13 Magento\Framework\View\Result\Page\Interceptor->renderResult() called at [vendor\magento\framework\App\Http.php:120]
#14 Magento\Framework\App\Http->launch() called at [generated\code\Magento\Framework\App\Http\Interceptor.php:23]
#15 Magento\Framework\App\Http\Interceptor->launch() called at [vendor\magento\framework\App\Bootstrap.php:264]
#16 Magento\Framework\App\Bootstrap->run() called at [pub\index.php:30]
</pre>