Custom fields in com_content does not display when editing article in front end

Question

I created a plugin to add a custom field following this answer. Works fine when I am logged in the backend and edit the article but the tab is not displaying when the article is being edited from the front. Am I missing something here or do I have to do it like the docs mention here

Plugin XML:

<?xml version="1.0" encoding="UTF-8"?>
<form>
    <fields name="attribs" >
        <fieldset name="custom" >
            <field name="full_article_image_overlay"
                type="editor"
                filter="safehtml"
                buttons="true"
                label="PLG_FULL_ARTILCE_IMAGE_TEXT"
                />
        </fieldset>
    </fields>
</form>

Plugin PHP:

function onContentPrepareForm($form, $data) {

        $app = JFactory::getApplication();
        $option = $app->input->get('option');

        switch($option) {

            case 'com_content':
                if ($app->isAdmin()) {
                        JForm::addFormPath(__DIR__ . '/forms');
                        //Show specific forms based on categories
                        $form->loadFile('content', false);
                }
                return true;

        }

        return true;
    }
}

Stored Data in 'attribs' column

{
  "show_title": "",
  "link_titles": "",
  "show_tags": "",
  "show_intro": "",
  "info_block_position": "",
  "show_category": "",
  "link_category": "",
  "show_parent_category": "",
  "link_parent_category": "",
  "show_author": "",
  "link_author": "",
  "show_create_date": "",
  "show_modify_date": "",
  "show_publish_date": "",
  "show_item_navigation": "",
  "show_icons": "",
  "show_print_icon": "",
  "show_email_icon": "",
  "show_vote": "",
  "show_hits": "",
  "show_noauth": "",
  "urls_position": "",
  "alternative_readmore": "",
  "article_layout": "",
  "show_publishing_options": "",
  "show_article_options": "",
  "show_urls_images_backend": "",
  "show_urls_images_frontend": "",
  "full_article_image_overlay": "<p>Test Test<\/p>"
}

Answer 1

In front article edit form there are only selected fields added. If you want to add something there you will have to use Template Overrides to edit this file: /components/com_content/views/form/tmpl/edit.php. This component for now does not load custom form fields automatically like com_content does.

Adding field in form.php layout of article view

If you have your data stored in attribs field (params fieldset in form) something like this should work:

<?php echo $this->form->renderField('YOUR_FIEL_DNAME', 'params'); ?>

Adding field field into article form object by plugin

To add custom field to Article Form you can use this tutorial: https://docs.joomla.org/Adding_custom_fields_to_core_components_using_a_plugin But remember that you still have to add proper field in the view.