Hello people,
I had installed a year ago the newsworth template.
At the front page there is a k2 module content with subtemplate video player (see the picture).
You click on the thumbs on the right side and the video of the specific articles appears. I don;t know the reason but this functionality stopped and now always appeared the video of the first article.
I found the deafult.php of the video player template and started the debuging.
I found that all this happens because when the javascript add the format=JSON at the end of every article in order to get the JSON data of every article I get an error
(0) Call to undefined method K2ModelItemlist::prepareJSONItem()
Is there a way to solve this problem?

Thanks a lot!

k2 2.10.3
Joomla 3.9.19

Finally, the problem was a custom template that I created to html/com_k2.
When I assign the default template to the category the format=JSON is working perfect and the video player of course,
but when I assign my custom template the things not working.

So I have to see what might be wrong with my custom template. Do I have to add my custom template com_k2 to a file like xml in order to the articles assigned to this template to have json format?

Thanks for your help Fotis.

Well I think that there is a bug.
If you have an article asign to a category, that in display settings has disabled the item navigation then you cannot get the article in a json format and you get the error,
(0) Call to undefined method K2ModelItemlist::prepareJSONItem()

How can I send you a private message for more information?

Hello Fotis, I see that the json format at the k2 blog is working perfect.

But I install a new joomla 3.9.19 in php 7.4, with k2 component (K2 v2.10.4[Dev Build 20200604]) and newsworth template and nothing else (not 3rd party plugin) and it has the same behaviour as I described in my earlier post. I think the bug is at the newsworth template.

You can see the demo site here: www.tennisgreece.gr
credentials admin / admin

To my official website I had found a solution via css and display: none the navigation control. So, if you don't have time, don't look it at all.

Thanks

Yes they work, cause the item navigation is enabled at the display settings of the category that two these articles belong to.

But if you login to thw backend and go to the category's display settings and disable the item navigation you get the error
(0) Call to undefined method K2ModelItemlist::prepareJSONItem()

Did you login to the backend and try it?

Perfect Fotis!
Can you send me the files you changed, cause this is a demo a site and I want to fix also the official site.

Thank you!

Thank you Fotis!!