MATLAB GUI - Button Press returning error

Question

I have a simple MATLAB GUI Code, find attached. All it does is when a button is pressed it runs a function.

However when I press this button twice, it is throwing an error

Undefined function 'GUI' for input arguments of type 'struct'.

Error in @(hObject,eventdata)GUI('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating uicontrol Callback

% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
 set(handles.pushbutton1, 'enable','off'); 
 output = randomFunction(); 
    a = 1

while(1)
   a = a+1
    if a == 4 
        break; 
    end

end
set(handles.pushbutton1, 'enable','on');

Does randomFunction change your current working directory? — Suever
Good call, It does, but I am planning on making this as a standalone GUI in future, how would I work on that avenue. THe random function. actually asks the user to choose a directory, because it works on images. — Jesh Kundem

Suever Suever · Accepted Answer · 2017-03-28T14:37:47

The issue is that randomFunction must either change the current working directory or modify your PATH such that the GUI function (GUI.m) is no longer on the path and able to be found when you click the button the second time.

If you'd like to stop this behavior you have two options

The preferred option would be to modify randomFunction to not make this modification. A function should always the user's environment to the way that it was before being called. You can easily do this by using onCleanup within randomFunction
```
function randomFunction()
    folder = pwd;
    cleanup = onCleanup(@()cd(folder));

    % Normal contents of randomFunction
end
```
The other option within randomFunction though is to never use cd. This is the best practice. You can use full file paths instead to access files
```
filename = fullfile(folder, 'image.png');
imread(filename)
```

If you can't modify randomFunction you can modify your callback to remember what the current directory was before calling the function and then change it back after randomFunction completes. I would actually recommend using onCleanup to do this to ensure that the directory is changed back even if randomFunction errors out

function pushbutton1_Callback(hObject, eventdata, handles)
    set(handles.pushbutton1, 'enable', 'off'); 

    % Make sure that when this function ends we change back to the current folder
    folder = pwd;
    cleanup = onCleanup(@()cd(folder));

    output = randomFunction(); 
    a = 1

    while(1)
       a = a+1
        if a == 4 
            break; 
        end

    end
    set(handles.pushbutton1, 'enable','on');

MATLAB GUI - Button Press returning error

1 Answers