K2 Item view —Call to undefined method K2HelperHTML::loadjQuery()

Question

my client has updated to the latest version of Joomla: 3.8.1 und K2 to 2.8.0. Frontend and Backend are working, but it is not possible to edit a k2 item or k2 category. List view is working, but not the edit view.

Here a stack trace:

Any Ideas?

UPDATE

Follow the idea given below, I could find that the cause of the error comes from a custom k2-plugin which I wrote for that client. Within the xml manifest file of that plugin those defined fields cause the trouble

<field 
  name="lnk_items" 
  type="litems" 
  default=""
  label="K2_DRAG_AND_DROP_TO_REORDER_ITEMS"
  description="…"/>


<field 
 name="lnk_category" 
 type="lcategoriesmultiple" 
 default="" 
 label="K2_SELECT_ONE_OR_MORE_CATEGORIES"
 description="…"/>

If I comment out those fields, no error appears, but the plugin cannot work as expected, too.

Answer 1

"items.php" no longer exists in K2 (as of 2.8.0). I think you have a problem in your libraries folder because of the Joomla update. It might be that you have some reminiscent files from a previous Joomla version. Please check this post - in short rename your old libraries folder and copy a fresh one from a Joomla zip file.

If that doesn't work, then try uninstalling and then re-installing K2 (instead of just updating). If I'm not mistaken, K2 does not delete its data when it's uninstalled. In any case, backup up your website is a must before doing such thing.

Answer 2

Based on the question mentions not found helper function in the admin and Joomla update to 3.8.1:

Is site update from versions prior to 3.7.x? That introduced Custom Fields plugin that has been a real pain in the site since it loads FE helpers without your intention to. So my first and only guess (or solve trace) would be:

1. looking for the existence of loadjQuery function all over the code;
2. check class name of class that it declared at;
3. checking other classes with the same name;
4. debugging which of those classes is loaded (put die(__FILE__); in the start of each of those files);
5. use debug_print_backtrace() to trace the path that app loading the file and try to overcome the issue.