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How use keyboard arrow keys to control the slider GUI in App Designer?

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tonybabel
tonybabel on 14 Feb 2019
Answered: Roche de Guzman on 8 Jan 2021
GUIslider.png
Hi,
I have trouble using keyboard input (like arrow keys) to control a slider GUI in App Designer. For example, when pressing the left arrow key, the slider cursor move to left and pressing the right arrow the slider cursor move to right. I'm trying to use switch/case but totally have no idea what need to be written under each 'case'. Please help! Thank you so much!
Below is the codes I grabbed from "code view" window in App Designer.
% Value changing function: Slider
function SliderValueChanging(app, event)
changingValue = event.Value;
set_param('Output','Value',num2str(changingValue));
end
% Key press function: UIFigure
function UIFigureKeyPress(app, event)
switch event.Key
case 'left arrow key'
??????
case 'right arrow key'
??????
end

Answers (2)

Rik
Rik on 14 Feb 2019
You can use this tester GUI to determine what you should put for the special keys. Don't forget the otherwise option to exit the function if you don't want to respond to other keys.
figure(1),clf(1)
set(gcf,'KeyPressFcn',@keycall)
function keycall(h,e)
disp(e.Key)
end
%rightarrow and leftarrow are the left and right arrow key names
  1 Comment
Rik
Rik on 18 Feb 2019
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Roche de Guzman
Roche de Guzman on 8 Jan 2021
Under the keypress fx callback:
function UIFigureKeyPress(app, event)
value = app.Slider.Value; % get the slider value
key = event.Key; % get the pressed key value
if strcmp(key,'leftarrow')
value = value-1; % left value
elseif strcmp(key,'rightarrow')
value = value+1; % right value
end
app.Slider.Value = value; % set the slider value
SliderValueChanging(app, event); % execute the slider callback
end

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