State Change Callback on Slider Causing Error if Changed Too Fast

I have a jslider with a state change callback. When I drag the slider thumb, code is executed to calculate an area under a curve using trapz. The slider controls the end point of the integral interval. If I scroll through the slider slowly, or even at a reasonable pace, the code runs fine and there are no errors. But if I drag the slider quickly, I get an error with the trapz function that makes me think the code is caught in an unfinished state from the previous state change and is having a hard time keeping up with the slider value changing. I've thought about changing the callback to a mouse released or something that wouldn't change continuously, but I like the value given in real time as the slider is dragged. Any suggestions?

Answer 1

[Rik]

Include a flag in your handles struct that returns the callback if there is already a callback being executed.

function your_slider_callback(hObject,eventdata)
handles=guidata(hObject);
if handles.isbusy
    return
end
handles.isbusy=true;
guidata(hObject,handles)

%rest of your callback function%

handles.isbusy=false;
guidata(hObject,handles)
end

[Jeremy]

I tried your suggestion and I get the following error:

"Not enough input arguments" on the last line of the following code

 function stopSlider_Callback(hObject, eventdata, handles ) 

      if handles.isbusy

[Rik]

In that case your callback doesn't automatically load the handles, so you'll have to do that yourself. I'll edit my answer.

[Jeremy]

Now I get the following error after the edit:

 Undefined function or variable 'toDouble'.

 Error in opaque/double (line 79)
    dbl = toDouble(opaque_array(1));

 Error in guidata (line 83)
 if isscalar(h) &&  ishghandle(h)

 Error in Moldy_v3/stopSlider_Callback (line 278)
        handles = guidata(hObject);

[Rik]

I don't understand why this error occurs. What version of Matlab are you using? And on what OS?

[Jeremy]

I think it has to do with the fact that I'm using a java javax.swing.JSlider. I found this article which discusses the toDouble function that is at the root of the error. I'm not sure why I didn't get any errors before the code you suggested, though. Most of what is discussed in the article is over my head.

[Rik]

What you can try is gcbf or even gcf as arguments to guidata, although I haven't worked with Java objects enough to understand your program structure.