How to define a "ValueChangingFcn" in a GUIDE definied slider

There is a "ValueChangingFcn" if I define a slider with uicontrol. I could not find it in the Property Inspector of the GUIDE slider.

Is there any way to define one for this slider as well?

Csaba

Answer 1

[Walter Roberson]

uicontrol does not have ValueChangingFcn. That callback is only for App Designer "web figures" and never for "traditional figures", but uicontrol exists only for traditional figures.

The App Designer analog of uicontrol sliders is uislider()

If you need to know when a user has stopped moving a uicontrol slider then code the Callback property to start a timer object with the appropriate timeout. If Callback gets called again before the timer expires then restart the timer. Either way, timer was active or not, proceed with the work you would have liked to have done with a ValueChangingFcn callback if those existed. In other words uicontrol slider's equivalent to ValueChangingFcn is Callback property.

When the timer callback gets called, do the work that you would have liked to do in a ValueChangedFcn callback. uicontrol slider has no property equivalent to ValueChangedFcn callback, so this timer work is how you can do the equivalent.

If you want ValueChangingFcn but not ValueChangedFcn then do not bother with the timer, just use Callback property.

[Csaba]

Walter, thank you. The Help is a bit misleading. "Slider Properties" does not say that it is valid only for uislider (however the examples are using uislider, but the difference is not emphasized).

Unfortunately I did not tried neither the uislider, nor the uicontrol slider, I just red the help and used the GUIDE slider. That is why I was mistaken.

I want to put different movie frames in the axes above the slider as the slider is moving.

The GUIDE slider calls callback when you release the thumb of the slider. So, I think the timer is not a good solution to follow the slider movement. It refreshes my movie axes when the mouse pointer is released, but not during the movement. It calls the callback several times if you push the slider arrow and do not release it, and this way it refreshes the axes as well. I want the same functionality when moving the thumb also.

[Walter Roberson]

Notice the description of the Parent property of https://www.mathworks.com/help/matlab/ref/matlab.ui.control.slider-properties.html

Parent container, specified as a Figure object created using the uifigure function, or one of its child containers: Tab, Panel, ButtonGroup, or GridLayout. If no container is specified, MATLAB calls the uifigure function to create a new Figure object that serves as the parent container.

[Walter Roberson]

To get updates while a uicontrol slider is moving, see https://www.mathworks.com/matlabcentral/answers/345396-how-to-update-an-edit-box-window-continuously-by-dragging-a-slider-in-matlab-gui

[Csaba]

Thanks Walter a lot. You put me on the right track. I accept your answer.

Nevertheless, for my original question I got the solution as follows (just for the record):

% --- Executes just before Sample is made visible.
function Sample_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   unrecognized PropertyName/PropertyValue pairs from the
%            command line (see VARARGIN)

% Choose default command line output for Sample
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);

%This line is added 
    addlistener(handles.Movie_slider, 'Value', 'PostSet',@(hObject, EventData) frame_renew(hObject,EventData, handles,frames));

end

function frame_renew(object,EventData, handles,frames)
    framenumber=round(handles.Movie_slider.Value);
% Corrected following Walter's suggestion    
%    cla(handles.Movie);
%    imshow(frames(framenumber).f,'Parent',handles.Movie );
    handles.Movie.Children.CData=frames(framenumber).f;
end

Remarks: I have two objects in GUIDE

"Movie" (axes) and "Movie_slider" (it is the slider).

"frames" is a structure with (n) elements, having individual frames of the movie (I use it as global variables - not included in the code -, but any other method would be fine).

You should also take care of the

Movie_slider.Min (should be 1)

and

Movie_slider.Max (should be maximum number of frames in the movie)

Somewhere in the GUIDE code you should open a file and read the movie and plot the first frame in the Movie axes (imshow).

It sometimes flickers, but works!

Thanks Walter again, putting me on the right track!

Csaba

[Walter Roberson]

For frames after the first, I recommend updating the CData property of the image handle, instead of cla / imshow . imshow() can be somewhat slow.

[Csaba]

Thanks, you are right. I have edited my code!