How to display the current picture above the upload field in SonataAdminBundle?

Question

I am using SonataAdminBundle (with Doctrine2 ORM) and I have successfully added a file upload feature to my Picture model.

I would like, on the Show and Edit pages, to display a simple <img src="{{ picture.url }} alt="{{ picture.title }} /> tag just above the relevant form field (provided that the Picture being edited is not new, of course), so that the user may see the current photo, and decide whether to change it or not.

After hours of research, I've been unable to figure out how to do it. I suppose I need to override some template, but I'm a bit lost... Can somebody give me a hint?

Thank you!

Here is the relevant section of my PictureAdmin class.

protected function configureFormFields(FormMapper $formMapper)
{
    $formMapper
        ->add('category', NULL, ['label' => 'Catégorie'])
        ->add('title', NULL, ['label' => 'Titre'])
        ->add('file', 'file', ['required' => false, 'label' => 'Fichier']) // Add picture near this field
        ->add('creation_date', NULL, ['label' => 'Date d\'ajout'])
        ->add('visible', NULL, ['required' => false, 'label' => 'Visible'])
        ->add('position', NULL, ['label' => 'Position']);
}

protected function configureShowFields(ShowMapper $showMapper)
{
    $showMapper
        ->add('id', NULL, ['label' => 'ID'])
        ->add('category', NULL, ['label' => 'Catégorie'])
        ->add('title', NULL, ['label' => 'Titre'])
        ->add('slug', NULL, ['label' => 'Titre (URL)'])
        ->add('creation_date', NULL, ['label' => 'Date d\'ajout'])
        ->add('visible', NULL, ['label' => 'Visible'])
        ->add('position', NULL, ['label' => 'Position']);
        // Add picture somewhere
}

Answer 1

I have managed to put the image above the field in the edit form. But my solution is a little bit specific, because I use Vich Uploader Bundle to handle uploads, so the generation of the image url was a little bit easier thanks to bundle helpers.

Let's look at my example, a film poster field in a film entity. This is part of my admin class:

//MyCompany/MyBundle/Admin/FilmAdmin.php

class FilmAdmin extends Admin {

protected function configureFormFields(FormMapper $formMapper)
{
 $formMapper
     ->add('title')
 ....
     ->add('poster', 'mybundle_admin_image', array(
                'required' => false,
                ))
}

mybundle_admin_image is handled by a custom field type, that is just a child of file type by setting it's getParent method: (don't forget to register your type class as a service)

//MyCompany/MyBundle/Form/Type/MyBundleAdminImageType.php

public function getParent()
{
    return 'file';
}

Then I have a template that extends Sonata's default styling, and I have it included in the admin class:

//MyCompany/MyBundle/Admin/FilmAdmin.php

public function getFormTheme() {
    return array('MyCompanyMyBundle:Form:mycompany_admin_fields.html.twig');
}

And finally I have a block for my custom image type that extends the basic file type:

//MyCompany/MyBundle/Resources/views/Form/mycompany_admin_fields.html.twig

{% block mybundle_admin_image_widget %}
{% spaceless %}
    {% set subject =  form.parent.vars.value %}
    {% if subject.id and attribute(subject, name) %}
        <a href="{{ asset(vich_uploader_asset(subject, name)) }}" target="_blank">
            <img src="{{ asset(vich_uploader_asset(subject, name)) }}" width="200" />
        </a><br/>
    {% endif %}
    {% set type = type|default('file') %}
    <input type="{{ type }}" {{ block('widget_attributes') }} {% if value is not empty %}value="{{ value }}" {% endif %}/>
{% endspaceless %}
{% endblock %}

This causes that a 200px wide preview of image (if exists) is shown above the upload field, linked to it's full size version opening in new tab. You can customize it as you want, e.g. adding a lightbox plugin.