Fix BO admin media bug : https://github.com/sonata-project/SonataAdminBundle/issues/5433

config/services.yaml

@@ -6,6 +6,7 @@
 parameters:
     locale: 'en'
     sonata.user.admin.user.controller: 'App\Controller\CRUD\CRUDController'
+    sonata.media.admin.media.class: 'App\Admin\MediaAdmin'
 
 services:
     # default configuration for services in *this* file
@@ -212,3 +213,9 @@ services:
     #           group: "Comptabilité"
     #           label: "Flux"
     #     public: true
+
+    # app.flash_messenger:
+    #     class: App\Listener\Flash
+    #     arguments: ["@session"]
+    #     tags:
+    #         - { name: kernel.event_listener, event: kernel.response }
\ No newline at end of file

src/Admin/MediaAdmin.php

+<?php
+namespace App\Admin;
+
+use Sonata\AdminBundle\Object\Metadata;
+use Sonata\MediaBundle\Admin\ORM\MediaAdmin as BaseMediaAdmin;
+use Sonata\MediaBundle\Provider\MediaProviderInterface;
+
+class MediaAdmin extends BaseMediaAdmin
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function getObjectMetadata($object)
+    {
+        $provider = $this->pool->getProvider($object->getProviderName());
+
+        $url = $provider->generatePublicUrl(
+            $object,
+            $provider->getFormatName($object, MediaProviderInterface::FORMAT_ADMIN)
+        );
+
+        return new Metadata($object->getName(), $object->getDescription(), $url);
+    }
+}