Get pixel location in UIAxes within app designer

In my app designer, I have a UIAxes to display an image. I also have an On/Off switch by the image. When the switch is On, I could click a pixel in the image to return the pixel coodinates in the codes for further calcualtion. When the switch is Off, click on the image won't return anything.

I'm stuck at connecting the swtich and coodinate picker. I also don't have a reliable solution to return pixel coodinates. Currently I'm following the example here,

            roiPOC = drawpoint(app.UIAxes);    %Use Mouse To Select a point ROI
            PosPOC=round(get(roiPOC,'Position'));    %Extract Coordinates of the point ROI
            delete(roiPOC);    %Delete the point ROI Marker
            drawnow;              % Force figure update       

but above codes are not stable, sometimes the point won't be deleted. Any thoughts please? I'm using Matlab 2020b.