MATLAB: Return data from GUIDE on figure close

delayguiguideMATLABoutputoutputfcnuiwait

I have a GUIDE generated UI in which I have wired up one of computed values, to handles and return it through automatically generated callback OutputFcn. When I run my UI, it computes the value and returns it to the command window immediately. The UI has interactive controls which will modify the output value, but it is not returned after the interactive controls are manipulated.

When I add uiwait(handles.figure1), then OutputFcn is not called until close, which is the desired behavior. Unfortunately when I do this the handles passed into OutputFcn is empty. When I omit the uiwait command from OpeningFcn, then the handles object passed to OutputFcn is populated as expected.

It seems that if OutputFcn is called while the figure is still open, then the handles object exists and can be referenced, however, if OutputFcn is not called until I close the figure, then the handles object points to a closed figure and I can no longer reference it.

Any advice to resolve this? Thanks!

Best Answer

To delay a GUIDE-GUI output until the GUI is closed, follow these steps. A functional demo is attached that produces an empty GUI and returns a hard-coded output when the GUI is closed. See comments in the m-file for help.

1) If your GUI does not already have a close request function, add one from within GUIDE by opening your GUI in GUIDE, right click the figure background, select View Callbacks, and the select CloseRequestFcn.

2) In the ..._OpeningFcn

function demoGui_OpeningFcn(hObject, eventdata, handles, varargin)
. . .
uiwait();  % add this to the end

3) In the ..._outputFcn

function varargout = demoGui_OutputFcn(hObject, eventdata, handles) 
varargout{1} = handles.output;
delete(hObject); % add this

4) In the ..._CloseRequestFcn you created from GUIDE,

function figure1_CloseRequestFcn(hObject, eventdata, handles) 
% delete(hObject);          % Remove this
handles.output = 3.1415926; % Produce or grab your outputs 
guidata(hObject, handles);  % Store the outputs in the GUI
uiresume()                  % resume UI which will trigger the OutputFcn

[Original answer has been edited]

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In your callback for edit1 you replace the handle with the value extracted from the handle. That is confusing at the very least.

MATLAB: How to cleanly exit from the OpeningFcn of a GUI if a certain condition is met

One can typically call the CloseRequestFcn of a GUI to cleanly exit from it. However, calling it directly from the OpeningFcn is not desirable for a clean exit because the GUI is not fully initialized at that point. After exiting from the OpeningFcn the OutputFcn of a GUI is called by the GUIDE execution infrastructure. At the end of this function, the initialization of a GUI is complete and it is safe to call the CloseRequestFcn.

As an example, consider the following implementation of the OpeningFcn and the OutputFcn. This example uses CloseRequestFcn to close the GUI. To generate a default CloseRequestFcn, open the GUI in GUIDE, right-click on the figure and select ViewCallbacks -> CloseRequestFcn. This will open the MATLAB file for the GUI. Modify CloseRequestFcn if needed, then save the MATLAB GUI file.

% --- Executes just before myGUI is made visible.
function myGUI_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 myGUI (see VARARGIN)
% Choose default command line output for myGUI
handles.output = hObject;
% if the user supplied 'exit' as an argument, save it in the handles
% structure
if ~isempty(varargin) && ischar(varargin{1}) && strcmp(varargin{1},'exit')
      handles.closeFigure = true;
end
% Update handles structure
guidata(hObject, handles);
% UIWAIT makes myGUI wait for user response (see UIRESUME)
% uiwait(handles.figure1);
% --- Outputs from this function are returned to the command line.
function varargout = myGUI_OutputFcn(hObject, eventdata, handles)
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% Get default command line output from handles structure
varargout{1} = handles.output;
% if the user suppled an 'exit' argument, close the figure by calling
% figure's CloseRequestFcn
if (isfield(handles,'closeFigure') && handles.closeFigure)
      figure1_CloseRequestFcn(hObject, eventdata, handles)
end
% - Executes when user attempts to close figure1.
function figure1_CloseRequestFcn(hObject, eventdata, handles)
% hObject    handle to figure1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% Hint: delete(hObject) closes the figure
delete(hObject);

The above solution relies on the OutputFcn being called right after the OpeningFcn when adequate inputs are not provided and the GUI must exit. If one wishes to stop the execution of OutputFcn by using UIWAIT, for cases where adequate inputs are provided, a conditional UIWAIT can be placed in the OpeningFcn. The corresponding UIRESUME can be placed in any of other functions as desired.

Best Answer

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MATLAB: Error using handle.handle/set Invalid or deleted object.

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