Now I prescribe the way

{% extends ":AdminBundle:admin_base.html.twig" %}

this is the directory path

 project/app/Resources/views/AdminBundle

And you need to register something here

 project/AdminBundle/Resources/views/admin_base.html.twig

Do so

 {% extends "../admin_base.html.twig" %}

I get an error

 Looks like you try to load a template outside configured directories (../admin_base.html.twig) in AppAdminBundle:Dashboard:main.html.twig at line 1.

    1 answer 1

    In general, it was necessary so, at random picked up.

     {% extends "AppAdminBundle::admin_base.html.twig" %}