Enable / Disable specific listbox item

Question

Dan 2014-10-13

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https://ww2.mathworks.cn/matlabcentral/answers/158480-enable-disable-specific-listbox-item

编辑： Amos 2023-4-18

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

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Answer 1

Image Analyst 2014-10-13

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You can't do that. The workarounds are the two you listed.

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Answer 2

Robert Cumming 2014-10-13

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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:

%

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Afifa Shaikh 2020-10-23

Matlab is not able to recognize the keyword 'str2html'

Undefined function or variable 'str2html'.

Andy 2020-10-23

See file exchange

https://uk.mathworks.com/matlabcentral/fileexchange/46755-str2html?s_tid=srchtitle

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Answer 3

Amos 2023-4-18

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https://ww2.mathworks.cn/matlabcentral/answers/158480-enable-disable-specific-listbox-item#answer_1217958

编辑：Amos 2023-4-18

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.