Overriding a .xml file in administrator

Question

So I 'm trying to override the articles.xml in my administrator folder. I figured out that I could create my own plugin and redirect it to another folder.
So here is what I did:

Creating a custom plugin.php

<?php
defined( '_JEXEC' ) or die( 'Restricted access' );
jimport('joomla.plugin.plugin');

class plgSystemmyPlugin extends JPlugin{
   
function onContentPrepareForm($form, $data) {
        jimport('joomla.form.form');
   JForm::addFormPath(JPATH_ADMINISTRATOR.DS.'components'.DS.'com_content/models/forms');
JForm::addFormPath(JPATH_ADMINISTRATOR.'/templates/isis/html/com_content/article');
    }
}
?>

and creating a xml file:

<?xml version="1.0" encoding="utf-8"?>
<extension version="3.1" type="plugin" group="system">
    <name>Custom Plugin</name>
    <author>Joomla! Project</author>
    <creationDate>November 2005</creationDate>
    <copyright>Copyright (C) 2005 - 2013 Open Source Matters. All rights reserved.</copyright>
    <license>GNU General Public License version 2 or later; see LICENSE.txt</license>
    <authorEmail>[email protected]</authorEmail>
    <authorUrl>www.joomla.org</authorUrl>
    <version>3.1.0</version>
    <description>PLG_SEARCH_CATEGORIES_XML_DESCRIPTION</description>
    <files>
        <filename plugin="customplugin">customplugin.php</filename>
        <filename>index.html</filename>
    </files>

</extension>

I tried to install it, but it doesn't work. I have already my xml file in my administrator/templates/isis/html/com_content/article.xml

Can anyone please help me fix this? I don't know how to get it to work, so it reads my custom article.xml instead of the original one.

I have been looking in this thread, but I dont know how to get it to work, I think im doing something wrong. enter link description here

Answer 1

To add additional custom fields to your article you can create a content plugin by following steps on this article

Or you can install this plugin and learn how to add the custom fields for joomla article from it.

To add custom fields for other component you can follow this documentation

To override the article.xml in the models/forms/ folder you can install this plugin and add your override file in the folder

/administrator/templates/system/forms/com_content/article.xml

for the admin side

and

/templates/system/forms/com_content/article.xml

for the frontend side