MATLAB: How to return values from .mlapp to the .m caller

appdesignerMATLAB

I made a matlab application (.m) for which I want to setup some parameters using a parameter window built with appdesigner (.mlapp). I was perfectly able to send values from .m to .mlapp, but I am not able to make the oposite i.e. return values from the .mlapp to .m.

My parameter window just contains 2 sliders.

There is probably something I dont understand. Can someone help me on this. Thanks

Best Answer

An App designer UI is just a class. You can add functions and properties to this however you wish and access these from the scope in which you create the UI object.

In fact, last time I checked the uneditable code of the app designer UI had the ghastly feature that all the uicomponent properties have public access so all you need to do is something like this:

myApp = App( );
sliderVal = myApp.slider1.Value;

You will need to edit that as appropriate for your app name, slider name within the app etc and I don't remember off-hand if the property is called 'Value' for an app designer slider, but I assume it is.

Related Solutions

MATLAB: App Designer How to “StartUp” within the App

(1) Two possibilities to reset your app to its default state:

https://www.mathworks.com/matlabcentral/answers/489003-reset-or-clear-property-values-in-app-designer#comment_763148

https://www.mathworks.com/matlabcentral/answers/489003-reset-or-clear-property-values-in-app-designer#answer_399598

I prefer the first. A simple example using a function called resetComponents:

classdef app1 < matlab.apps.AppBase
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure        matlab.ui.Figure
        EditFieldLabel  matlab.ui.control.Label
        EditField       matlab.ui.control.EditField
        Button          matlab.ui.control.Button
    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 = 'UI Figure';
            % Create EditFieldLabel

            app.EditFieldLabel = uilabel(app.UIFigure);
            app.EditFieldLabel.HorizontalAlignment = 'right';
            app.EditFieldLabel.Position = [382 282 56 22];
            app.EditFieldLabel.Text = 'Edit Field';
            % Create EditField

            app.EditField = uieditfield(app.UIFigure, 'text');
            app.EditField.Position = [453 282 100 22];
            % Create Button

            app.Button = uibutton(app.UIFigure, 'push');
            app.Button.Position = [129 282 100 22];
            app.Button.Text = 'Reset';
            app.Button.ButtonPushedFcn = @app.resetButtonCallback;
            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
        
        function resetComponents(app)
            % Create EditFieldLabel
            app.EditFieldLabel = uilabel(app.UIFigure);
            app.EditFieldLabel.HorizontalAlignment = 'right';
            app.EditFieldLabel.Position = [382 282 56 22];
            app.EditFieldLabel.Text = 'Edit Field';
            % Create EditField
            app.EditField = uieditfield(app.UIFigure, 'text');
            app.EditField.Position = [453 282 100 22];
            % Create Button
            app.Button = uibutton(app.UIFigure, 'push');
            app.Button.Position = [129 282 100 22];
            app.Button.Text = 'Reset';
            app.Button.ButtonPushedFcn = @app.resetButtonCallback;
            
            % Or, alternatively, instead of redefining each component, just figure out all
            % properties which could be changed by the user and reset them to their
            % defaults:
            %

            % app.EditField.Value = '';
            %
            % Simpler here, but takes more work for more complicated apps.
        end
        
        function resetButtonCallback(app, ~, ~)
            resetComponents(app);
        end
    end
    % App creation and deletion
    methods (Access = public)
        % Construct app
        function app = app1
            % 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

(2) You can access a callback function if you have access to an instance of the app and you are calling from a location allowed by the function's Access attribute (e.g. Public, Private, etc).

Example 1: You cannot call a callback function from within a static method, because the static method does not have access to an instance of the app.

Example 2: You cannot call a callback function externally if its Access attribute is Private.

MATLAB: Calling a function defined in a m-file from within appdesigner app, with the app object as function input

Your GUI (like all AppDesigner GUIs) has a pass-by-reference behavior (so it behaves like a handle class). That means the line you show modifies the original object, instead of creating a new one when the function is called.

You could create a GUI that doesn't work this way by using the normal figure class, so what is generally meant by a 'programmatic GUI', or GUIs created with GUIDE. For an overview of your options for GUI design, see this. For more information about pass-by-reference vs pass-by-value, see Comparison of handle and value classes in the documentation.

Best Answer

Related Solutions

MATLAB: App Designer How to “StartUp” within the App

MATLAB: Calling a function defined in a m-file from within appdesigner app, with the app object as function input

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