Slider listener using GUIDE

I need to update the variable frame2display dynamically. But the following code isnt working. How should I modify it? I would like to stick with using GUIDE. Thanks.

function getMCavi_Callback(hObject, eventdata, handles)

handles = guidata(hObject);

[fname,~,~]  = uigetfile('*.avi*','Select the motion stablized .avi video',pwd); 
VidObj_stbl = VideoReader(fname);
nframes_all=round((VidObj_stbl.Duration)/(1/VidObj_stbl.FrameRate));

for m=1:nframes_all
    temp=(readFrame(VidObj_stbl,'native'));
    imframes_all(:,:,m)=temp(:,:,1);
end;
imframes_all = double(imframes_all);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%confusing portion %%%%%%%%%%%%%%%%%%%%%%%%%%%
handles.slider_value = addlistener(handles.slider_frameNum,'Value', 'PostSet', ...
                                      @(hObject,eventdata)test2('slider_frameNum_Callback',hObject,eventdata,guidata(hObject)));
slider_value = handles.slider_value;
display(slider_value);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

frame2display = slider_value;
if frame2display == 0
    frame2display = 1; 
end

img = squeeze(imframes_all(:,:,frame2display));
imagesc(img, 'Parent', handles.MCimages); axis equal tight off; colormap gray    

guidata(hObject,handles)

% --- Executes on slider movement.
function slider_frameNum_Callback(hObject, eventdata, handles)

handles = guidata(hObject);
slider_value = get(hObject,'Value');
handles.slider_value = slider_value; 
guidata(hObject,handles)

Answer 1

[Walter Roberson]

I would not use addlistner for that. I would use the normal Callback property of the uicontrol('style', 'slider')

You should save imframes_all somewhere, and the Callback for the slider should extract the fetch slider value, pull out the corresponding frame from imframes_all, and image() or imshow() it into the appropriate axes. You would initialize the slider value and call the Callback "manually" to get the process going.

[Dawn]

Hi Walter, thanks for the response. However I need more help with the syntax. I dont really understand how to modify the GUIDE template asn shown in my question to extract the slider value.

[Walter Roberson]

function getMCavi_Callback(hObject, eventdata, handles)

    handles = guidata(hObject);

    [fname,~,~]  = uigetfile('*.avi*','Select the motion stablized .avi video',pwd); 
    VidObj_stbl = VideoReader(fname);
    nframes_all=round((VidObj_stbl.Duration)/(1/VidObj_stbl.FrameRate));

    for m=1:nframes_all
        temp=(readFrame(VidObj_stbl,'native'));
        imframes_all(:,:,m)=temp(:,:,1);
    end;
    handles.imframes_all = double(imframes_all);
    set(handles.slider_frameNum, 'Value', 1);
    guidata(hObject, handles);

    slider_frameNum_Callback(handles.slider_frameNum, [], handles);   %trigger a plot

    function slider_frameNum_Callback(hObject, eventdata, handles)

    handles = guidata(hObject);
    slider_value = get(hObject,'Value');

    frame2display = max(1, slider_value);

    img = squeeze(handles.imframes_all(:,:,frame2display));

    ax = handles.MCimages;
    imagesc(img, 'Parent', ax);
    axis(ax, 'equal', 'tight', 'off');
    colormap(ax, gray)

[Dawn]

THANKS! This works! The only change needed is to round the slider_value so that it can be passed into imframes_all without error.

Just curious, so when is it suitable to use addlistener instead?

[Walter Roberson]

Personally I never use addlistener when an existing interface handles the situation. addlistener feels too "backdoor" to me, and it is not at all transparent as to what will happen in any given situation, since a wide variety of different code might have registered listeners for an event.