MATLAB: How to modify the handles structure (GUI) from an external function

guidehandlesmodify handles

Hi,

I am developing a GUI. I can modify the handles structure (for example handles.variable1 = 2) within callbacks. However I am not able to do the same within an external function. E.g., this does not work:

function [matrix, indexVector] = myFunction(handles)
handles.variable1 = 1;

It is important to note that myFunction does not belong to the GUI callbacks, it is simply a function I have created in another m file. When I call it I can read the handles struture (actually im passing them as a parameter) but when I try to modify them the modification is not recorded.

Best,

-MRR

Best Answer

function [matrix, indexVector] = myFunction(handles)
handles.variable1 = 1;
guidata(handles.figure1,handles)

Where figure1 is the 'Tag' of the figure. You want to make sure that you assign the handles structure to the right place (i.e. the figure). hObject is dynamic, handles will always have the field for the figure.

Related Solutions

MATLAB: Trouble with function called from a GUI callback fonction

Claude - look closely at the order in which handles is updated. The

 function CallbackFunction(hObject, eventdata, handles)

is called passing in the latest (at the time) version of handles. This parameter (along with the other two) are passed in to your function

 function myFunction(hObject, eventdata, handles)

where the code updates the handles object and then saves it using

 guidata(hObject, handles);

But then we return back to your CallbackFunction and maybe do something, and then calls

 guidata(hObject, handles);

But which version of handles is this? This is the copy that was passed into this function when CallbackFunction was called. It is not the updated version from your call to myFunction since myFunction does not return the updated handles structure, and your code probably doesn't refresh handles (after this call to myFunction) with

 handles = guidata(hObject);

So you can do at least two different things - return the updated handles structure from myFunction by changing its signature to

 function [handles] = myFunction(hObject, eventdata, handles);

and so your code would become something like

 function CallbackFunction(hObject, eventdata, handles) 
 ...
 handles = myFunction(hObject, eventdata, handles);
 ...
 guidata(hObject, handles);   % in case you've updated handles again

 end % function

Or you can refresh your local copy as

 function CallbackFunction(hObject, eventdata, handles) 
 ...
 myFunction(hObject, eventdata, handles);
 handles = guidata(hObject);
 ...
 guidata(hObject, handles);   % in case you've updated handles again
 end % function

Hopefully, one of the above solutions will work for you!

MATLAB: OpeningFcn not saving handles

This is occurring because in your OpeningFcn, you are calling "guidata" after calling your callback function.

guidata can manage only one variable at any time. Subsequent calls to guidata(object_handle,data) overwrite the previously stored data.

For this reason, your call to "guidata" after your callback function is overwriting the new handles values. Instead, call "guidata" and then call your callback function.

function test_OpeningFcn(hObject, eventdata, handles, varargin)
handles.output = hObject;
guidata(hObject, handles);
pushbutton1_Callback(hObject, eventdata, handles) %call after guidata so not overwritten

Best Answer

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MATLAB: Trouble with function called from a GUI callback fonction

MATLAB: OpeningFcn not saving handles

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