MATLAB Creating Graphical User Interfaces

12 Manage Application-Defined Data

'Position',[0.4 0.3 0.2 0.1],...

'String','Display Values',...

'Callback',@button_callback);

end

function slider_callback(hObject,eventdata)

data = guidata(hObject);

data.val = hObject.Value;

data.diffMax = hObject.Max - data.val;

guidata(hObject,data);

end

function button_callback(hObject,eventdata)

data = guidata(hObject);

display([data.val data.diffMax]);

end

When the user moves the slider, the slider_callback function calls guidata to

retrieve a copy of the stored struct array. The next two lines of code modify the struct

array. The last line in the function replaces the stored struct array with the modified

copy.

When the end users clicks the push button, the button_callback function calls

guidata to retrieve a copy of the stored struct array. Then it displays the two values

stored in the array.

Use guidata in a GUIDE UI

GUIDE uses guidata to store a struct array called handles, which contains all the

UI components. MATLAB passes the handles array to every callback function. If you

want to use guidata to share additional data, then add fields to the handles structure

in the OpeningFcn callback. To modify your data in a callback function, modify the

handles array, and then store it using guidata. This slider callback function shows

how to modify and store the handles array in a callback function.

function slider1_Callback(hObject,eventdata,handles)

handles.myvalue = 2;

guidata(hObject,handles);

end

To see a full example of a GUIDE UI that uses the guidata function, follow these steps

to copy and examine the code.

1 Set your current folder to one to which you have write access.