Share variables between callbacks and save when GUI window is closed

Hi. I am developing a larger GUI, but have made a simplified part of it to make the problem easier. In one uicontrol I want the user to be able to define some values that should be accessed later in the GUI. However, it seems that if I define a value in the while loop it can not be accesssed in a callback function. Any tips on how to make this work?

clc;
clear all; 
close all; 
end

S.d = dialog('Position',[200 200 800 200],'Name','My Dialog',...
    'WindowStyle','normal');

 S.btn = uicontrol('Parent',S.d,...
               'Position',[200 20 70 25],...
               'String','Add',...
               'Callback',{@mydef_function,S});

   S.btnadd = uicontrol('Parent',S.d,...
                  'Position',[400 20 70 25],...
                  'String','Save',...         
          'Callback',{@mysave_func,S});

 S.btnexit = uicontrol('Parent',S.d,...
               'Position',[600 20 70 25],...
               'String','Close',...
               'Callback',{@my_exit_function,S});           

           bOK = true;
           while(bOK)
               uiwait(S.d)
               guidata(S.btnadd)

          if ~isempty(S.btn.UserData)
            bOK=false;
          end

          end

           function mydef_function(src,event,S)
           uiresume(S.d)
           val = 2; 
           guidata(src,val)
           end

           function mysave_func(src,event,S)
           uiresume(S.d)
           S.val = guidata(S.btn)
           guidata(src,S.val)
           end

           function my_exit_function(src,event,S) 
           uiresume(S.d);
           src.UserData = 1;
           end

[proczell]

It should be specified that the variable seems to be deleted when the figure is closed, and I want to access the data..

[Adam]

When using guidata you can only have one thing saved as guidata. Subsequent calls to guidata with an argument to save will overwrite the previous one. This sounds useless as stated, but guidata is generally used within GUIDE with the 'handles' struct containing all the GUI components being the thing that is always saved, often after having first being retrieved and added to since you can attach any custom fields you want to the struct in addition to GUI handles.

In your case you don't have 'handles' so you would need to create your own struct to use guidata and ensure that you always save the same one and that you retrieve it with e.g.

handles = guidata( src );
handles.val = 2;
guidata( src, handles )

to add a value to it and put it back in the GUI without losing the other data that was also stored on it.

As per Walter's answer though, this data will be linked to the lifetime of the GUI still.

Answer 1

[Walter Roberson]

Note that dialog() creates a new figure, so when you use guidata(src, ...) in the callbacks for uicontrol on that dialog figure, you are storing data against the dialog figure, and that data is going to disappear when the figure is closed. You should have a CloseRequestFcn callback which should store the data somewhere that the other code can get at it.

inputdlg() and questdlg() with this slightly differently: they store the data against the dialog figure they create, and declare that if the dialog figure gets deleted that the input failed; if it was not deleted at the time they leave the uiwait() due to the uiresume() then they fetch the data from the dialog figure and then destroy the dialog figure.

[proczell]

This makes a lot of sense. Will try that out. Do you know if it is possible to use uitables in inputdlg() or questdlg()?

[Walter Roberson]

inputdlg() and questdlg() have no ability to use uitables. Both of them are routines that construct dialog figures and set up appropriate text on the page and appropriate uicontrol and callback routines, and then do uiwait(), fetch the data from the dialog figure, and return the data. You can read their source code.

[proczell]

I see. As it would have required a lot of work to re-model the whole UI, I basically solved the problem by saving the variables to a *.mat file and the loading it in the other callback function. I know this is not a very good solution, but it does the job for now, at lest. Thanks for the other ideas, will use them in the next project!

Answer 2

[Birdman]

https://www.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html

[proczell]

I have read this document several times, but could not find any helpful methods. Maybe missing some obvious part here, but could not find a solution there. But thanks anyway, good document.

[Birdman]

Which version of MATLAB are you using?

[proczell]

2017A

[Birdman]

Well, in that case, I suggest you to use App Designer. It is so much easier to built applications rather than using old fashioned way. I built an application for you where you can plot a vector dependent of a vector that you enter, for instance

[1 2 3 4 5]

Now, what I want you to do is to run the application. Firstly, click on Plot Properties On button to do the necessary settings for the plot named Title. Then, in the Edit Field part, enter

 1,3,5,7,9

exactly with commas as I wrote and then click on Plot. The output is calculated as

output=2*input-1;

Then, click on Mean of Output button, which is a different callback in the application. In the below numeric field, you will see the mean of the output vector.

After first trial, go to Code View of the app and see how I stored the output from first callback button. It is stored in a struct of the app. Check the notations and other stuff.

[proczell]

Thank you, will definately check this out!

[Birdman]

Ok, let me know the results. As I said, it is really easy to do that kind of stuff in App Designer.