help with gui share data

i read the link to share data among callbacks, but i still couldnt understand and apply it to my code

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

in the code and gui, i want to have the drawrectangle function print the position output to 4 editable columns (because i want the user to be able to edit the position with the columns too)

but i can't make the code transferable to other callback functions

can anyone explain to me and also give an example fix to the code?

Answer 1

[Rik]

For general advice and examples for how to create a GUI (and avoid using GUIDE), have look at this thread.

GUIDE uses guidata, which you can think of as a sort of mat file you store with your figure. You can only save 1 variable, so it makes sense to use a struct, as you can use fieldnames to have some more information in your variable (as opposed to a cell, where it would matter in what order the variables are stored). GUIDE automatically generates the callback functions in such a way that the third input will be the dynamically loaded struct. That means you only need to store back data at the end of your callback function. If you do that, that data will be available to the other callback functions.

[Adrian Lee]

from what i read in the forum you have linked, the reason guide isnt used is that it has limited flexibility and will be removed in future releases

could you give an example of the "callback functions in such a way that the third input will be the dynamically loaded struct"?

I'm confused about that

[Rik]

The first input argument of a callback is a handle to the object that caused the callback to be triggered, and the second input argument is the eventdata. GUIDE uses that to define callbacks like this:

callback=@(hObject,eventdata) CallbackFunction(hObject,eventdata, guidata(hObject) );

This loads the data from guidata each time the callback is triggered. That is what I meant.

You can trivially do this yourself:

function CallbackFunction(hObject,eventdata)
handles=guidata(hObject);

%do things here


%store data to the figure so other callbacks can access this data as well
guidata(hObject,handles)
end

[Adrian Lee]

so, as an example, this is the opening function in guide

do i go

function v1_gui_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to v1_gui (see VARARGIN)

% Choose default command line output for v1_gui
handles.output = hObject;
data = guidata(hobject)
data.a = 1+1;
data.a2 = 2+2;

% Update handles structure
guidata(hObject, handles);
guidata(hobject, data);


% UIWAIT makes v1_gui wait for user response (see UIRESUME)
% uiwait(handles.figure1);
end

and

function xpos_Callback(hObject, eventdata, handles)
% hObject    handle to xpos (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
data = guidata(hobject);
disp([data.a data.a2]);
% Hints: get(hObject,'String') returns contents of xpos as text
%        str2double(get(hObject,'String')) returns contents of xpos as a double
end

sorry, i'm unfarmiliar with guide data sharing

this is taken from the opening function of a blank guide template

[Rik]

For some reason you insist on sticking with GUIDE. I don't understand why you would want to, but that is your choice.

As the automatically generated documentation of the OpeningFcn already states: you already have the struct with all required data: handles. So your edit was close, except for the fact that you are overwriting the handles struct when you store your variable called data to the figure with guidata.

function v1_gui_OpeningFcn(hObject, eventdata, handles, varargin)
handles.output = hObject;
%either this or handles.data.a and handles.data.a2, pick what makes sense for you
handles.a = 1+1;
handles.a2 = 2+2;
% Update handles structure
guidata(hObject, handles);

You don't need to use data=guidata(hObject); in your callback function as I already explained: the callbacks that are generated by GUIDE already do that.

The main problem with GUIDE is very visible here: you didn't bother reading the comments, because there are too many of them, and most are too complex (or, in the case of eventdata, wrong). You didn't read what the different inputs to your function mean. I would really encourage you to step away from GUIDE. As far as I can tell it has remained mostly unchanged for the last 20 years.

[Adrian Lee]

ah, this explanation is clear to me now

it isnt that i insist on sticking to guide, i have already started looking into appdesigner

i do not have a good grasp of handles, the share callbacks link do not really give a good explanation as only one example and giving the pros n cons of each method