Matlab App Designer Virtual Joystick via the change of image position from incoming data via ROS

I try to make a virtual joystick in Matlab App Designer with the help of images that I have added Image3 as main image and top of it, I have added the Image4 which it will move positions according to my joystick Axes1-Axes2 values from ROS subscriber topic.

I have written a main while loop to see all of the changes in real time on Matlab Appdesigner via drawnow() function at the of the main loop which it will help me to see the joystick image to move on the Virtual Joystick Panel in the picture below.

However, I get these errors:

Index in position 1 exceeds array bounds. Index must not exceed 1.

virtual_joystick_movement(app, double(app.stored_logitech1_axes1), double(app.stored_logitech1_axes1) );

updateGUIjoystick(app)

This is the function I wrote.

function virtual_joystick_movement(app, x_vr_joy, y_vr_joy )
            % [left bottom width height]
            default_imagePos = [183 215 143 133];
            
            % Boundary positions for joystick can go as max and min
            x_max = 225;
            %y_max = 257;
            x_min = 141;
            %y_min = 173;

            default_x = default_imagePos(1);
            default_y = default_imagePos(2);

            get_pos_x = app.Image4.Position(1); % Current Position of X for the joy image
            get_pos_y = app.Image4.Position(2); % Current Position of Y for the joy image

            new_pos_x = get_pos_x + x_vr_joy; % app.stored_logitech1_axes1
            new_pos_y = get_pos_y + y_vr_joy; % app.stored_logitech1_axes2
            
            %customPosition = app.Image4('Position', [left bottom width height]); % Current new position of image
            %customPosition.Position = []; % define your new position for the image

            customPosition = app.Image4('Position', [get_pos_x get_pos_y default_x default_y]);
            %customPosition.Position = [new_pos_x new_pos_y default_imagePos(3) default_imagePos(4)]; % define your new position for the image
            
            if x_vr_joy > 0 && customPosition(1) <= x_max && customPosition(1) >= x_min
                customPosition.Position = [new_pos_x new_pos_y default_imagePos(3) default_imagePos(4)]; % define your new position for the image
            elseif x_vr_joy < 0 && customPosition(1) <= x_max && customPosition(1) >= x_min
                customPosition.Position = [new_pos_x new_pos_y default_imagePos(3) default_imagePos(4)]; % define your new position for the image
            elseif x_vr_joy == 0 || x_vr_joy == -0
                customPosition.Position = [183 215 143 133]; % define your new position for the image
            end
            
        end

I will be very glad if someone would guide me to show me the correct way to apply this virtual joysyick feature in Matlab Appdesigner.

[Dolon Mandal]

Can you try the following code:

function virtual_joystick_movement(app, x_vr_joy, y_vr_joy)
    % [left bottom width height]
    default_imagePos = [183 215 143 133];
    
    % Boundary positions for joystick can go as max and min
    x_max = 225;
    %y_max = 257;
    x_min = 141;
    %y_min = 173;
    default_x = default_imagePos(1);
    default_y = default_imagePos(2);
    get_pos_x = app.Image4.Position(1); % Current Position of X for the joy image
    get_pos_y = app.Image4.Position(2); % Current Position of Y for the joy image
    new_pos_x = get_pos_x + x_vr_joy; % app.stored_logitech1_axes1
    new_pos_y = get_pos_y + y_vr_joy; % app.stored_logitech1_axes2
    
    % Update the position of app.Image4 directly
    app.Image4.Position = [get_pos_x get_pos_y default_x default_y];
    
    if x_vr_joy > 0 && app.Image4.Position(1) <= x_max && app.Image4.Position(1) >= x_min
        app.Image4.Position = [new_pos_x new_pos_y default_imagePos(3) default_imagePos(4)];
    elseif x_vr_joy < 0 && app.Image4.Position(1) <= x_max && app.Image4.Position(1) >= x_min
        app.Image4.Position = [new_pos_x new_pos_y default_imagePos(3) default_imagePos(4)];
    elseif x_vr_joy == 0 || x_vr_joy == -0
        app.Image4.Position = [183 215 143 133];
    end
end