Enable / Disable specific listbox item

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Dan
Dan on 13 Oct 2014
Edited: Amos on 18 Apr 2023
Is there a way to disable an item in a listbox. Basically I want to have a listbox that displays a number of available items for selection but want a subset of these items to be greyed out (disabled).
I can (of course) just check for the forbidden item AFTER the user has selected it and tell him that this item is unavailable. But that seems in elegant. Alternatively, I could simply not list forbidden items to begin with but.... also inelegant.
Ideas?
Thanks!
Dan

Accepted Answer

Image Analyst
Image Analyst on 13 Oct 2014
You can't do that. The workarounds are the two you listed.

More Answers (2)

Robert Cumming
Robert Cumming on 13 Oct 2014
By using this FEX you can make it look like things are disabled:
function test
myStr{1} = 'Allowed';
myStr{2} = str2html ( 'Not Allowed', 'italic', true, 'colour', '#A0A0A0' );
myStr{3} = 'Allowed';
myStr{4} = 'Allowed';
myStr{5} = 'Allowed';
allowed = [1 0 1 1 1]; % flags of items allowed or not.
uicontrol ( 'style', 'listbox', 'position', [0 0 400 200], 'String', myStr, 'Callback', {@checkcb allowed} )
end
function checkcb ( obj, event, allowed )
if allowed(obj.Value) == 0
errordlg ( 'Not allowed' );
obj.Value = find ( allowed, 1, 'first' );
end
end
See example image:
%
  3 Comments
Afifa Shaikh
Afifa Shaikh on 23 Oct 2020
Matlab is not able to recognize the keyword 'str2html'
Undefined function or variable 'str2html'.
Andy
Andy on 23 Oct 2020
See file exchange
https://uk.mathworks.com/matlabcentral/fileexchange/46755-str2html?s_tid=srchtitle

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Amos
Amos on 18 Apr 2023
Edited: Amos on 18 Apr 2023
As of 2023a, there still isn't (yet?) an enable-state vector, but:
On styling, further to Robert Cummings answer above, and from §Version History: https://au.mathworks.com/help/matlab/ref/matlab.ui.control.dropdown-properties.html
"R2023a: Style drop-down component items
Create styles for drop-down components using the uistyle function, and add the styles to individual items or entire drop-down components using the addStyle function."
On behaviour, (not new, but for completeness) it's then easy, if clumsy, to disregard/reverse selection using ValueChangedFcn and event.PreviousValue (above link: §Callbacks).
When the visual cue doesn't disuade selection, one hopes that user-adaptation follows quickly. The facility to programmatically re-open the droplist could be useful here, but expect item-level enable-state control would be much higher on everyone's wishlists.

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