help with gui share data

2020 11 17
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更新时间：2020 11 18
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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?

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Rik
Rik 2020-11-17

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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.

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Adrian Lee
Adrian Lee 2020-11-17
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
Rik 2020-11-17
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
Adrian Lee 2020-11-18
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
Rik 2020-11-18
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
Adrian Lee 2020-11-18
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

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