Getting GUI Slider updates while dragging

Question

Norton Allen 2012-10-23

3
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回答： AG 2019-2-20

Is there a straightforward method to get updates on a slider's position while it is being dragged? The standard callback gets called only after the drag is complete and the button has been released.

I'm thinking of using the ButtonDownFcn to start a polling loop checking the slider's value. (Then how do I detect mouse up?)

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Sean de Wolski 2012-10-23

ButtonDownFcn is disabled over an enabled uicontrol

Norton Allen 2012-10-24

编辑：Norton Allen 2012-10-24

Matt, what I'm trying to do is get a slider where the app updates while the slider is moving, for example the way a browser updates while you are moving the scroll bar.

Sean, I did discover that ButtonDownFcn is not the answer pretty quickly too!

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Answer 1

Sean de Wolski 2012-10-23

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This can be done easily with addlistener

h = uicontrol('style','slider','callback',@(src,evt)disp(get(src,'value')));
addlistener(h,'Value','PreSet',@(~,~)disp('hi'));

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Mohamad Roslan Mohd Roshdi 2016-1-24

Hi How to get the slider update value into variable?

Stephen23 2016-1-24

Mohamad Roslan Mohd Roshdi also created a question here: http://www.mathworks.com/matlabcentral/answers/264979-continuous-slider-callback-how-to-get-value-from-addlistener

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Answer 2

AG 2019-2-20

0
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The following worked for me. I get a 'live' scroll-bar update by calling this within another function:

slider_value = get(gcf.Children(j), 'Value');

...where j is the value of the UIcontrol corresponding to the scroll. You can find out which UIControl it is in the figure by putting a break in the code and using:

gcf.Children

This could also be ascertained in run-time using:

for j = 1:length(gcf.Children)
    get(gcf.Children(j), 'Tag')
end

which will return a char array with the Tag of each of the children which could then be compared using strcmp(), for example. I've done this using a GUI created with GUIDE.