i am getting this error on developer mode but works in default
Exception #0 (Magento\Framework\Config\Dom\ValidationException): Theme layout update file
XML declaration allowed only at the start of the document
Line: 31
First line xml, is line 31 before that its html comment
<?xml version="1.0" encoding="UTF-8"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="admin-2columns-left" xsi:noNamespaceSchemaLocation="../../../../../../../lib/internal/Magento/Framework/View/Layout/etc/page_configuration.xsd">
<update handle="editor"/>
<body>
<referenceContainer name="content">
<block class="Apptha\Airhotels\Block\Adminhtml\Uploadvideo\Edit" name="airhotels_uploadvideo_edit"/>
</referenceContainer>
<referenceContainer name="left">
<block class="Apptha\Airhotels\Block\Adminhtml\Uploadvideo\Edit\Tabs" name="airhotels_uploadvideo_edit_tabs">
<block class="Apptha\Airhotels\Block\Adminhtml\Uploadvideo\Edit\Tab\AddVideo" name="airhotels_uploadvideo_edit_tab_addvideo"/>
<action method="addTab">
<argument name="name" xsi:type="string">addvideo_section</argument>
<argument name="block" xsi:type="string">airhotels_uploadvideo_edit_tab_addvideo</argument>
</action>
<!--CedAddTab-->
</block>
</referenceContainer>
</body>
</page>
Thanks
Best Answer
I moved the xml declaration at the top of the page and its working now. Leaving this here if someone else have same issue.