GUI loses state when destroyed and recreated

This USED to work several days ago, but somehow I broke it.

I have a GUI which I created in App Designer. The GUI is called from a Matlab function via a button push. The GUI has its own "Exit" button, or I can just click the X in the upper right corner. Until recently, the state of the GUI was preserved across creations and deletions, but now it "forgets" its state when destroyed, i.e., radio buttons and other components revert to their initial state. What did I break?

I deleted the whole GUI and re-created it in App Designer with just three radio buttons, and that version also loses state. Here is the code:

In my main menu GUI:

function SearchOptionsButtonPushed(~,~)     % this is the button to launch the GUI
    SearchOptions;
end

Here is the SearchOptions class:

classdef SearchOptions < matlab.apps.AppBase
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure        matlab.ui.Figure
        MountTypePanel  matlab.ui.container.Panel
        ButtonGroup     matlab.ui.container.ButtonGroup
        RADECButton     matlab.ui.control.RadioButton
        AZELButton      matlab.ui.control.RadioButton
        OffButton       matlab.ui.control.RadioButton
    end
    % Callbacks that handle component events
    methods (Access = private)
        % Selection changed function: ButtonGroup
        function ButtonGroupSelectionChanged(app, event)
            global AzEl_mode;
            selectedButton = app.ButtonGroup.SelectedObject;
            %disp(selectedButton);
            AzEl_mode = get(event.NewValue, 'Tag' );
            disp(AzEl_mode);          
        end
    end
    % Component initialization
    methods (Access = private)
        % Create UIFigure and components
        function createComponents(app)
            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 640 480];
            app.UIFigure.Name = 'MATLAB App';
            % Create MountTypePanel
            app.MountTypePanel = uipanel(app.UIFigure);
            app.MountTypePanel.Title = 'Mount Type';
            app.MountTypePanel.Position = [52 359 260 103];
            % Create ButtonGroup
            app.ButtonGroup = uibuttongroup(app.MountTypePanel);
            app.ButtonGroup.SelectionChangedFcn = createCallbackFcn(app, @ButtonGroupSelectionChanged, true);
            app.ButtonGroup.Position = [21 23 221 34];
            % Create OffButton
            app.OffButton = uiradiobutton(app.ButtonGroup);
            app.OffButton.Tag = '0';
            app.OffButton.Text = 'Off';
            app.OffButton.Position = [17 6 42 22];
            app.OffButton.Value = true;
            % Create AZELButton
            app.AZELButton = uiradiobutton(app.ButtonGroup);
            app.AZELButton.Tag = '1';
            app.AZELButton.Text = 'AZ/EL';
            app.AZELButton.Position = [70 6 46 22];
            % Create RADECButton
            app.RADECButton = uiradiobutton(app.ButtonGroup);
            app.RADECButton.Tag = '2';
            app.RADECButton.Text = 'RA/DEC';
            app.RADECButton.Position = [136 6 59 22];
            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end
    % App creation and deletion
    methods (Access = public)
        % Construct app
        function app = SearchOptions
            % Create UIFigure and components
            createComponents(app)
            % Register the app with App Designer
            registerApp(app, app.UIFigure)
            if nargout == 0
                clear app
            end
        end
        % Code that executes before app deletion
        function delete(app)
            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end
end
        

All very basic, just three radio buttons, but when I destroy the GUI, the state is lost. The AzElMode global is used elsewhere in my app.

How do I preserve the state? I found a very old discussion on this at the following link, but it's 12 years old:

https://blogs.mathworks.com/videos/2010/12/10/how-to-save-and-restore-state-of-a-gui-in-matlab/

Answer 1

[Kurt]

Found the solution. Change the GUI callback function to read as follows:

function GUIButtonGroupSelectionChanged(app, event) % or whatever your GUI is named
    global AzEl_mode;
    AzEl_mode = get(event.NewValue, 'Tag' );     
end

Then in the parent class where the component is initialized, add the following function:

function GUIButtonPushed(~,~)
    GUIPanel = GUI;            % instantiate the GUI
    global AzEl_mode;
    if (AzEl_mode == 1)
        GUIPanel.AZELButton.Value = true;            % your button names may vary
    elseif (AzEl_mode == 2)
        GUIPanel.AZELButton.Value = true;
    end
end

Note that there is no need to include the "AzEL_mode == 0" case, because the GUI already defaults to 0 when it is initialized.

Pulldown menus can be handled the same way, except the Value is set to one of the drop-down item values, as follows:

global scan_mode_index
if (scan_mode_index == 1)
    GUIPanel.Dropdown.Value = 'Notary Sojak'

where the global scan_mode_index was saved in the callback function.

There may be better methods that don't require the use of globals, but this works for me.