MATLAB: “Next Button” and “command window” in App Designer

app designerMATLAB

I am very new to Matlab App designer and have two questions. I appreciate any help.

I have a series of images located in a folder. I would like to show them one at a time and then go to the next one by pressing the "Next" button. How can I program the "Next" button?
I would like to see the values of variables in AppDesigner code. I know it's doable via debug mode and placing a break point at the line in which that variable is. But I don't see the values by hovering the mouse (although this feature is active in normal Matlab mode). Also, I don't really know where is the command window for App designer mode? I think it's not the same as Matlab command window because when I put variable's name there, it's undefined.

Thank you for any help

Best Answer

Make an app and add two properties. Filelist and currentidx and a placeholder for image in the app.

Make a function called load next image. Set it as the callback for your next button.

On startup load the filelist and display the first image.

properties (Access = private)
    currentidx = 1; %set to 1 initially
    Filelist = {};
end
function load_next_image(app)
    idx = mod(app.currentidx + 1,length(app.Filelist));
    if idx == 0
        idx = 1;
    end
    app.load_image_at_index(idx);
end
function load_image_at_index(app,j)
    app.currentidx = j;
    impath = app.Filelist{j};
    app.Image.ImageSource = impath;
end
% add a startup function by clicking AppInputArguments button in code view
function startupFcn(app,varargin)
    % app.Filelist = {'C:\test\test.png'}; % assign your list
    app.load_image_at_index(1);
end

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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!!

Best Answer

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