Accessing an ROI move listener in another function so to delete it

Hello.

I am using listeners to allow a user to reshape an ellipse ROI (i.e. orange shape) to then apply a mask to an image (then perfrom analysis on that part of the image). I'm using appdesigner

I store the centre and radius of the ROI as global variables (public properties)

I have a pushbutton that allows the user to view and change the shape of the ROI. This is my code.

            %get current stored ROI ellipse parameters
            r=app.ROIradius;
            xc=app.ROIxc;
            yc=app.ROIyc;
            ax=app.UIAxes3;          %This is the UIAxes my image is on.
            IM=double(getimage(ax));
            [sy,sx]=size(IM);
            
            %Delete any previous ROI
            t=findobj(ax,'Type','images.roi.Ellipse');
            delete(t);
            
            %Draw ROI using current saved parameters and add a listener to allow it to be changed
            h = images.roi.Ellipse(ax,'Center',[xc yc],'Semiaxes',[r r],'Color','r','StripeColor','g','LineWidth',1);         %1/e^2 = 1.699xfwhm  
            h.FaceAlpha = 0.3;
            h.DrawingArea=[1 1 sx sy];
            h.FixedAspectRatio=true;        %ensure a circle
                    
            % Listen for mouse movement of the ROI
            l=addlistener(h,'MovingROI',@app.allevents);

Then in my allevents function that is attached to the listener: (Perhaps I should have a MovedROI, rather than moving?)

            function allevents(app,src,evt)
            evname = evt.EventName;
            switch(evname)
                case{'MovingROI'}
                    disp(['ROI moving Current Center: ' mat2str(evt.CurrentCenter)]);
                    disp(['ROI moving Current SemiAxes: ' mat2str(evt.CurrentSemiAxes)]);
                    c=evt.CurrentCenter;  
                    app.ROIxc=c(1);
                    app.ROIyc=c(2);
                    r=evt.CurrentSemiAxes;
                    app.ROIradius=r(1);   
                    ...
                case ..
            end

I then have another button to create the mask.

            r=round(app.ROIradius); xc=round(app.ROIxc); yc=round(app.ROIyc);
            circ = drawcircle('Center',[xc,yc],'Radius',r);
            BW = createMask(circ,IM);
            figure
            subplot(1,2,1)
            imshow(BW)
            IM(~BW) = 0 ;      %Apply the mask
            subplot(1,2,2)
            hi=0.8*max(IM(:))
            lo=min(IM(:))
            imshow(IM,[lo hi])

My issue is that the listener is still present. does it matter? I can't work out how to delete it from another pushbutton and still do what I want to do.

[Jason]

Anyone?

Answer 1

[Tommy]

Assuming you don't want to delete the ellipse, you could instead delete the listener within your button's callback function. You can pass the listener to that function in a number of ways, one of which is to save the listener within (or as) a property of your app. Another possibility is to directly pass the listener to your button's callback property. I hope the following helps illustrate this, even though it is simply a script and not tied to an object like in appdesigner:

f = uifigure;
ax = axes(f, 'Position', [0.1, 0.6, 0.8, 0.4]);
b = uibutton(f,...
    'Position', [0.1*f.Position(3), 0.1*f.Position(4), 0.8*f.Position(3), 0.4*f.Position(4)],...
    'ButtonPushedFcn', @buttonpress);

% Draw ROI
h = images.roi.Ellipse(ax, 'Center', [0.5 0.5],...
    'Semiaxes', [0.3 0.3]);

% Listen for mouse movement of the ROI
l = addlistener(h, 'MovingROI', @allevents);

% Update button's callback, passing in the listener l
b.ButtonPushedFcn = {b.ButtonPushedFcn, l};

function allevents(~, evt)
    evname = evt.EventName;
    if strcmp(evname, 'MovingROI')
        disp(['ROI moving Current Center: ' mat2str(evt.CurrentCenter)]);
        disp(['ROI moving Current SemiAxes: ' mat2str(evt.CurrentSemiAxes)]);
    end
end

function buttonpress(src, ~, l)
    if nargin > 2 % if nargin > 3 in appdesigner, I believe
        delete(l)
        % src.ButtonPushedFcn = @buttonpress;
    end
end

[Jason]

Hi Tommy, thanks, I will explore your idea. I actually dont need the ellipse so would it actually be easier to delete this in the 2nd button callback?

[Tommy]

Possibly easier, as you could use findobj() as you do above instead of storing the ellipse or passing it to the callback directly. I kind of figured the decision to delete the ellipse or not would depend on whether you want it to continue to show within the axes.

[Jason]

So I've an idea from Tommy.

when I create the listener, I assign it to an app property:

app.l=addlistener(h,'MovingROI',@app.allevents);

This then appears to allow me to delete it in other functions / button callbacks

L=app.l;
delete(L);