Handle.listener, how to update code?

Hi, I have an old MathWorks code that I did not write and contains handle.listener in it. It appears that Matlab has phased out this function and was replaced by addlistener. In the code below, I am getting an error in the line with the handle.listener function, how can I update the code so it continues to work as before??

Thank you!!

function updateAncestorListeners(h_group,update_fcn)
%updateAncestorListeners Set up listeners to ancestors. 
%   updateAncestorListeners(H_GROUP,UPDATE_FCN) sets up listeners to all
%   ancestors of H_GROUP that have Position, XLim, or YLim properties. H_GROUP
%   is an hggroup object. UPDATE_FCN is a function handle that is called when
%   any of the ancestor properties change.
% 
%   It's important to use updateAncestorListeners when you are drawing objects
%   in a way that may depend on the current Position, XLim, or YLim properties
%   of ancestors. If these properties change, you need to redraw your
%   object. Using updateAncestorListeners makes the code drawing objects more
%   robust to user actions like zooming and resizing.


%   $Revision $  $Date: 2005/05/27 14:07:37 $

% Clear the old listeners.
setappdata(h_group, 'AncestorPositionListeners', []);

h_parent = get(h_group, 'Parent');
root = 0;
listeners = [];
property_list = {'Position', 'XLim', 'YLim'};
while h_parent ~= root
  % Some ancestor objects might not have Position properties.
  properties = get(h_parent);
  for k = 1:numel(property_list)
    property = property_list{k};
    if isfield(properties, property)
      parent_handle = handle(h_parent);
      listener = handle.listener(parent_handle, ...
                                 parent_handle.findprop(property), ...
                                 'PropertyPostSet', update_fcn);
      if isempty(listeners)
        listeners = listener;
      else
        listeners(end + 1) = listener;
      end
    end
  end
  h_parent = get(h_parent, 'Parent');
end

setappdata(h_group, 'AncestorPositionListeners', listeners);

Copyright 2005 The MathWorks, Inc.

[Kevin Chng]

Hi,

I found a similar question been asked in the past.

https://www.mathworks.com/matlabcentral/answers/244728-how-do-i-update-my-code-from-using-handle-listener-to-using-addlistener

 listener = addlistener(parent_handle, ...
                                 parent_handle.findprop(property), ...
                                 'PropertyPostSet', update_fcn);

I'm not sure will it work or not because i don't have your input to try it out. Hope it help you.

[Kaden]

Thanks! Unfortunately I saw this earlier and wasn't able to get my code running with it. I believe my error is with "update_fcn" . Any ideas on how this input needs to be modified to go from a handle.listener to a addlistener accepted input? I didn't fully understand the fourth argument difference.

Thanks!

[Kevin Chng]

Hi Kaden, do you mind provide h_group and update_fcn script/data file for me try out?

Answer 1

[Divyajyoti Nayak]

Hi Kaden,

To update code from using ‘handle.listener’ to ‘addlistener’, the ‘eventName’ or the third argument needs to be changed. Here’s the documentation of ‘addlistener’ which describes the requirements of the input arguments:

https://www.mathworks.com/help/matlab/ref/handle.addlistener.html?s_tid=doc_ta

Hence, the new code would be something like:

listener = addlistener(parent_handle, parent_handle.findprop(property), 'PostSet', update_fcn);

It is important to note that the parent class whose property is being listened to must set the the ‘GetObservable’ and ‘SetObservable’ attribute. Only then, listening to these properties is possible.