Help with undefined function error in context menu in App Designer?

I'm having a problem getting context menues to work in a Matlab App. I'm unclear on the exact usage and examples and questions in the community haven't helped. It is apparently not seeing my Menu Selected Function. The same code works in a standard figure, but fails in the app.UIFigure. I'm trying to create context menus associated with specific plots in the UIAxes.

The error is "Undefined function 'Line1' for input arguments of type 'matlab.ui.container.Menu'.

Error using matlab.ui.internal.controller.WebMenuController/fireActionEvent

Error while evaluating Menu Callback."

The code is:

classdef TestApp1 < matlab.apps.AppBase
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure       matlab.ui.Figure
        DropDown       matlab.ui.control.DropDown
        DropDownLabel  matlab.ui.control.Label
        UIAxes         matlab.ui.control.UIAxes
    end
    
    methods (Access = private)
        function Line1(app,src,event,K)
            disp('This is Line 1')
            disp(src)
            disp(event)
            disp(K)
        end
        function Line2(app,src,event)
            disp('This is Line 2')
        end
    end
    
    % Callbacks that handle component events
    methods (Access = private)
        % Value changed function: DropDown
        function DropDownValueChanged(app, event)
            CM=uicontextmenu(app.UIFigure);
            M1=uimenu(CM,"Text","Line1");
            M1.MenuSelectedFcn = {@Line1, 3};
            M2=uimenu(CM,"Text","Line2");
            M2.MenuSelectedFcn = @Line2;
            value = app.DropDown.Value;
            P1=plot(app.UIAxes,[1 2],[1 1],'r-',"ContextMenu",CM);
            hold(app.UIAxes,'on')
            P2=plot(app.UIAxes,[1 3],[2 2],'b-',"ContextMenu",CM);
            ylim(app.UIAxes,[0 3]);
            xlim(app.UIAxes,[0 4]);
        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 UIAxes
            app.UIAxes = uiaxes(app.UIFigure);
            title(app.UIAxes, 'Title')
            xlabel(app.UIAxes, 'X')
            ylabel(app.UIAxes, 'Y')
            zlabel(app.UIAxes, 'Z')
            app.UIAxes.Position = [127 68 387 321];
            % Create DropDownLabel
            app.DropDownLabel = uilabel(app.UIFigure);
            app.DropDownLabel.HorizontalAlignment = 'right';
            app.DropDownLabel.Position = [45 427 65 22];
            app.DropDownLabel.Text = 'Drop Down';
            % Create DropDown
            app.DropDown = uidropdown(app.UIFigure);
            app.DropDown.ValueChangedFcn = createCallbackFcn(app, @DropDownValueChanged, true);
            app.DropDown.Position = [125 427 100 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 = TestApp1
            % 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

Answer 1

[Voss]

Use "@app.Line1" and "@app.Line2" instead of "@Line1" and "@Line2", since those functions are app methods.

See below:

classdef TestApp1 < matlab.apps.AppBase
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure       matlab.ui.Figure
        DropDown       matlab.ui.control.DropDown
        DropDownLabel  matlab.ui.control.Label
        UIAxes         matlab.ui.control.UIAxes
    end
    
    methods (Access = private)
        function Line1(app,src,event,K)
            disp('This is Line 1')
            disp(src)
            disp(event)
            disp(K)
        end
        function Line2(app,src,event)
            disp('This is Line 2')
        end
    end
    
    % Callbacks that handle component events
    methods (Access = private)
        % Value changed function: DropDown
        function DropDownValueChanged(app, event)
            CM=uicontextmenu(app.UIFigure);
            M1=uimenu(CM,"Text","Line1");
            M1.MenuSelectedFcn = {@app.Line1, 3};
            M2=uimenu(CM,"Text","Line2");
            M2.MenuSelectedFcn = @app.Line2;
            value = app.DropDown.Value;
            P1=plot(app.UIAxes,[1 2],[1 1],'r-',"ContextMenu",CM);
            hold(app.UIAxes,'on')
            P2=plot(app.UIAxes,[1 3],[2 2],'b-',"ContextMenu",CM);
            ylim(app.UIAxes,[0 3]);
            xlim(app.UIAxes,[0 4]);
        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 UIAxes
            app.UIAxes = uiaxes(app.UIFigure);
            title(app.UIAxes, 'Title')
            xlabel(app.UIAxes, 'X')
            ylabel(app.UIAxes, 'Y')
            zlabel(app.UIAxes, 'Z')
            app.UIAxes.Position = [127 68 387 321];
            % Create DropDownLabel
            app.DropDownLabel = uilabel(app.UIFigure);
            app.DropDownLabel.HorizontalAlignment = 'right';
            app.DropDownLabel.Position = [45 427 65 22];
            app.DropDownLabel.Text = 'Drop Down';
            % Create DropDown
            app.DropDown = uidropdown(app.UIFigure);
            app.DropDown.ValueChangedFcn = createCallbackFcn(app, @DropDownValueChanged, true);
            app.DropDown.Position = [125 427 100 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 = TestApp1
            % 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

[Dan Zabetakis]

Bingo! I would never have figured that out. Thanks.

[Voss]

You're welcome!