Stop the execution of a function with a push button (GUIDE)

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Hiya!
I have a program, which analyzes a series of images extracting data from them. Now, I have been asked to make a gui in order to be more easily used. I have gotten stuck in the part where I call the program itself from the gui (which, by the moment, is a separate program (m-file)).
The calling of the program is easy, and it works. But, the proccess is long, and sometimes the user wants to stop it, in order to change configuration, for example. I can't do the cancelling part. Here is a scheme of what I've got, and what do I want
[GUIDE]
button -> Calls program.m (and it runs well)
button2 -> Stops program.m (this doesn't work) by changing the 'closing' variable to 1
[program.m]
while i< number of images if 'closing' == 1 -> exit program if not -> analyze the i image
Thank you in advance for your time and your response

Accepted Answer

Alfonso Nieto-Castanon
Alfonso Nieto-Castanon on 24 May 2015
Edited: Alfonso Nieto-Castanon on 24 May 2015
Using drawnow within program.m processing loop flushes the event queue so your pushbutton callback gets evaluated (otherwise the pushbutton callback will not be evaluated until program.m finishes its computations).
Of course, in addition to this, you need to make sure that your closing variable accessed from within program.m and from the pushbutton callback function are actually the same variable in the same workspaceworkspace. One simple way to do this would be something like:
in guide set pushbutton callback to:
'set(gcbo,''userdata'',1)'
and in program.m use something like:
set(handlepushbutton,'userdata',0);
i=1;
while i< numberofimages
% your iterative computation here
drawnow
if get(handlepushbutton,'userdata') % stop condition
break;
end
i=i+1;
end
  6 Comments
Alfonso Nieto-Castanon
Alfonso Nieto-Castanon on 25 May 2015
Edited: Alfonso Nieto-Castanon on 25 May 2015
if the cancelling action does not work and you are seeing in the command window the line set(gcbo,'userdata') being displayed that probably means that you made your pushbutton callback to simply display that line instead of executing it. To have your callback execute that line you can:
a) edit the properties of your pushbutton and set the callback property to the string
'set(gcbo,''userdata'',1)'
(with the single quotes as displayed above; when the callback property of an uicontrol object is a string, matlab will evaluate that string when a callback action is generated)
or b) edit the properties of your pushbutton and set the callback property to the function handle
@btnStop_Callback
and then within the body of the function btnStop_Callback type the line
set(gcbo,'userdata',1);
(as displayed here, i.e. without the initial quotes or the double single quotes of the other example; when the callback property of an uicontrol object is a function handle, as guide does by default, matlab will invoke the callback function in this handle when a callback action is generated)
My guess is that you might have left the pushbutton callback property set to a function handle as in case (b) above, but then within the body of that function you included the string 'set(gcbo,''userdata'',1)' (as in case (a) above), so Matlab ends up simply displaying that line in the command window when a callback action is generated...

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More Answers (2)

Image Analyst
Image Analyst on 24 May 2015
I have not found a way to do it with a pushbutton. Using it to set a flag, like "finishNow", that you can check in your intensive loop, does not seem to work. The only way I can get something like that to work is to have a checkbox. So you do something like
% Clear flag and make it visible.
set(handles.chkFinishNow, 'Value', 0);
set(handles.chkFinishNow, 'Visible', 'on');
% Now the intensive loop
for k = 1 : 1000000
% Heavy duty code.
% At and of loop, see if user wants to quit
if get(handles.chkFinishNow, 'Value')
% User checked the box
break; % exit the loop
end
end
% Clear flag and make it invisible.
set(handles.chkFinishNow, 'Value', 0);
set(handles.chkFinishNow, 'Visible', 'off');

Walter Roberson
Walter Roberson on 24 May 2015

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