Trying to add callback function in class

I am attempting to create a class the will have two line ROI objects. This class should have a callback function for when the lines are moved by the user. I am able to add a listener to the lines but only if the callback function is static.

Is it possible to do this without using a static method? Ultimatly I would like to use the callback method to compare the positions of the two lines as one of them is moved.

classdef imageRange < handle

    properties
        region double
        line1
        line2
        rect
        X double
    end

    methods
        function obj = imageRange(axes, dataAxes)
            x = dataAxes{1,4};
            y = dataAxes{2,4};
            midpoint = mean([x(1),x(3)]);

            obj.X = floor(midpoint);

            obj.rect = rectangle(axes,'Position',[obj.X,y(1),...
                ceil(midpoint)-floor(midpoint), y(3) - y(1)]);
            obj.rect.EdgeColor = [0,0,0,0];
            obj.rect.FaceColor = [.5,.5,.5];
            obj.rect.FaceAlpha = .1;

            obj.line1 = drawline(axes,'Position',[floor(midpoint), y(1); ...
                floor(midpoint), y(3)],'Color',[0.6350 0.0780 0.1840], ...
                'InteractionsAllowed','translate', ...
                'MarkerSize',.1, ...
                'LineWidth',1);

            addlistener(obj.line1, 'MovingROI', @(src,event)obj.allevents(src,event));

            obj.line2 = drawline(axes,'Position',[ceil(midpoint), y(1); ...
                ceil(midpoint), y(3)],'Color',[0 0.4470 0.7410], ...
                'InteractionsAllowed','translate', ...
                'MarkerSize',.1, ...
                'LineWidth',1);

            obj.region = dataAxes{1,5};
        end
    end

    methods (Static)
        function allevents(src,event)
            event.PreviousPosition(1,1)
        end
    end
end

Answer 1

[Manikanta Aditya]

Hi @Ethan Favorite,

Yes, you can achieve this without using a static method. You can define the callback function as a regular method within your class and use an anonymous function to pass the object instance to the callback. Here's how you can modify your class:

classdef imageRange < handle
    
    properties
        region double
        line1
        line2
        rect
        X double
    end
    
    methods
        function obj = imageRange(axes, dataAxes)
            x = dataAxes{1,4};
            y = dataAxes{2,4};
            midpoint = mean([x(1),x(3)]);
            obj.X = floor(midpoint);
            obj.rect = rectangle(axes,'Position',[obj.X,y(1),...
                ceil(midpoint)-floor(midpoint), y(3) - y(1)]);
            obj.rect.EdgeColor = [0,0,0,0];
            obj.rect.FaceColor = [.5,.5,.5];
            obj.rect.FaceAlpha = .1;
            obj.line1 = drawline(axes,'Position',[floor(midpoint), y(1); ...
                floor(midpoint), y(3)],'Color',[0.6350 0.0780 0.1840], ...
                'InteractionsAllowed','translate', ...
                'MarkerSize',.1, ...
                'LineWidth',1);
            addlistener(obj.line1, 'MovingROI', @(src,event)obj.allevents(src,event));
            obj.line2 = drawline(axes,'Position',[ceil(midpoint), y(1); ...
                ceil(midpoint), y(3)],'Color',[0 0.4470 0.7410], ...
                'InteractionsAllowed','translate', ...
                'MarkerSize',.1, ...
                'LineWidth',1);
            addlistener(obj.line2, 'MovingROI', @(src,event)obj.allevents(src,event));
            obj.region = dataAxes{1,5};
        end
        
        function allevents(obj, src, event)
            % Callback function to handle the event
            disp('Line moved');
            disp(['Previous Position: ', num2str(event.PreviousPosition)]);
            disp(['Current Position: ', num2str(event.CurrentPosition)]);
            
            % Compare positions of the two lines
            pos1 = obj.line1.Position;
            pos2 = obj.line2.Position;
            disp(['Line 1 Position: ', num2str(pos1)]);
            disp(['Line 2 Position: ', num2str(pos2)]);
        end
    end
end

In this updated version, the allevents method is a regular method of the class, and the listener is set up using an anonymous function that passes the object instance (obj) to the callback. This way, you can access the properties and methods of the class within the callback function.

[Ethan Favorite]

Thank you so much! This worked perfectly