MATLAB: How to draw line with a mouse in the UI of the UIAxes in App Designer

drawline()

Using drawline() i have attached a callback function that allows a user to draw lines on the axes. Initially, clicking the button pops up a new window to carry out the drawing, and so I specified the axes: app.UIAxes. This does not seem to work, and I get the following error: "Error using images.roi.internal.ROI/parseInputs

ROI parent must be a valid Axes object.".

I am using R2019a of MATLAB.

Best Answer

It works fine in r2019b; there are quite a few limitations to UIAxes prior to r2019b which may be causing the problem.

        function ButtonPushed(app, event)
            
            % Draw line
            drawline(app.UIAxes)
            
        end

Related Solutions

MATLAB: App Designer: How to use a camera in different Callbacks

Hi,

Folllowing is the code and app design

classdef app1 < matlab.apps.AppBase
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure  matlab.ui.Figure
        UIAxes    matlab.ui.control.UIAxes
        UIAxes2   matlab.ui.control.UIAxes
        Button    matlab.ui.control.Button
    end
    
    properties (Access = public)
        cam;
    end
    
    % Callbacks that handle component events
    methods (Access = private)
        % Code that executes after component creation
        function startupFcn(app)
            app.UIAxes2.Visible = 'off';
            evalin("base", 'clear cam');
            app.cam = webcam;
            frame = snapshot(app.cam);
            im = image(app.UIAxes, zeros(size(frame), 'uint8'));
            axis(app.UIAxes, 'image');
            preview(app.cam, im);
        end
        % Button pushed function: Button
        function ButtonPushed(app, event)
            img = snapshot(app.cam);
            image(app.UIAxes2, img);
            app.UIAxes2.Visible = 'off';
        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 = 'UI Figure';
            % Create UIAxes
            app.UIAxes = uiaxes(app.UIFigure);
            title(app.UIAxes, 'Title')
            xlabel(app.UIAxes, 'X')
            ylabel(app.UIAxes, 'Y')
            app.UIAxes.Position = [26 270 300 185];
            % Create UIAxes2
            app.UIAxes2 = uiaxes(app.UIFigure);
            title(app.UIAxes2, 'Title')
            xlabel(app.UIAxes2, 'X')
            ylabel(app.UIAxes2, 'Y')
            app.UIAxes2.Position = [25 43 300 185];
            % Create Button
            app.Button = uibutton(app.UIFigure, 'push');
            app.Button.ButtonPushedFcn = createCallbackFcn(app, @ButtonPushed, true);
            app.Button.Position = [447 249 100 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 = app1
            % Create UIFigure and components
            createComponents(app)
            % Register the app with App Designer
            registerApp(app, app.UIFigure)
            % Execute the startup function
            runStartupFcn(app, @startupFcn)
            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

Error you are facing instantiates that the code is not able to access the camera object at that instant.

Hope it helps!!

MATLAB: Connecting to a serial port in App Designer

Hi,

The issue when accessing rel.Value is your file is saved as app1, while you are using app to access rel's Value. Use app1 instead, I guess this solves your issue.

Instead of connecting to serial port at each callback, you can use StartupFcn callback of UIFigure to do the work for you. You can add the callback by clicking on callback icon in the toolstrip.

Hope this helps!

Best Answer

Related Solutions

MATLAB: App Designer: How to use a camera in different Callbacks

MATLAB: Connecting to a serial port in App Designer

Related Question