Is there a way to edit the own items of an editable uidropdown, where mutiple items can be the same value?

I made a quick example to demonstrate my problem.Is there a way to make something like this:

fig = uifigure;
dropdown = uidropdown(fig,"Editable","on");
dropdown.Items = ["Test_1","Test_2","Test_3","Test_3"];
dropdown.ValueChangedFcn = @(src,event)example_function(src,event);

function example_function(src,event)
    % currently something like this is not implemented and in my understanding there isn't a workaround for it
    % in this special usecase where multiple identically items can be in
    % one instance of uidropdown(why a workaround likely isn't possibly)
    
    % Is there a reason why something like this isnt implemented: 
    % dropdown.Items{selected/clicked on} -> event.IndexOfClickedItem: ["Test_1"->1, "Test_2"->2, "Test_3"->3, "Test_3"->4]
    
    index = event.IndexOfClickedItem; 
    src.Items{index} = src.Value;
end

[Mario Malic]

Check ItemsData property, it may help you to index into Items.

[Jonas Schütz]

I already tried it with ItemsData but there isn't a specific way to acess the needed index and at the end you get the same problem like described.I tried a workaround using ItemsData but at the end it doesn't work because there can be multiple same Items. Or is there something like src.ItemsData.Value for the ValueChangedFcn?

Answer 1

[Cris LaPierre]

There is a way to do this. As suggested, use the ItemsData property. You need to first define this when creating your drop down. Internally, the src and event values are the corresponding value from the ItemsData property.

fig = uifigure;
dropdown = uidropdown(fig,"Editable","on");
dropdown.Items = ["Test_1","Test_2","Test_3","Test_3"];
% Define the ItemsData property with a value for each element in Items.
dropdown.ItemsData = 1:4;
dropdown.ValueChangedFcn = @(src,event)example_function(src,event);


function example_function(src,event)
    
    index = event.Value;
    src.Items{index} = src.Value; % Be sure this statement is doing what you want 
end

The final line of code in your function will generate an error. I believe you have to replace the entire array of Items, and not just a single value. To do what I think you are trying to do, you'll have to do that in steps. That might look like this:

Items = src.Items;
Items{index} = num2str(src.Value);
src.Items = Items;

[Cris LaPierre]

To add additional details, here are the values of src and event inside the callback function. In this case, I selected the 3rd item in the dropdown menu to trigger the callback.

src = 

  DropDown (Test_3) with properties:

              Value: 3
              Items: {'Test_1'  'Test_2'  'Test_3'  'Test_3'}
          ItemsData: [1 2 3 4]
           Editable: on
    ValueChangedFcn: @(src,event)example_function(src,event)
           Position: [100 100 100 22]

  Show all properties


event = 

  ValueChangedData with properties:

            Value: 3
    PreviousValue: 1
           Edited: 0
           Source: [1×1 DropDown]
        EventName: 'ValueChanged'

[Jonas Schütz]

The goal is/was to make a somewhat very compact editfield for multiple labels or strings:

% Let's say If I select 
dropdown.Items{1} = "Test_1" 

% as a next step I want to edit the value inside the ui/app ( because it's an editable uidropdown) to 'Time in s'
% because it represents a label, which you want to change inside the ui/app
dropdown.Items{1}= 'Time in s' % change will be made via UI not code

If I then select "Test_2 or Items{2} via. the UI after I edited the first value, the changes to Items{1} will be reseted and not saved. Thats the reason my codes comes into place. I want to save the corresponding change in its index

dropdown.Items

so I can later select it again and my edit is still in its place. Maybe its unnessecary complicated but I don't know a better solution for a compact editfield.

The problem is if I just keep selecting and don't edit the dropdown your solution will work

src.Value && event.Value

will always be the needed index. But as soon as I edit the dropdown, both will change to the edited value in that example "Time in s " and I don't have acess to the needed index anymore. I hope I made it a bit more clear to understand.

I dont undestand why its working like this because its making an editable dropdrown somewhat more useless. I would expect that the changes you are making with your edit will stay in its place, then the code wouldn't be needed in the first place. Thats probably why its a bit confusing:

index = event.IndexOfClickedItem; 
src.Items{index} = src.Value; % here src.Value will change because of the edit you are making to string in the UI 

event.Value % will also change to edited value, I think src.Value and event.Value are the same

Also src.Value will not error out if it is an character vector, so perhaps you have to convert it.

[Cris LaPierre]

Not sure I fully follow, but I think a callback function like this gets close to what you are describing. You can at least play around with this to see if you get the behavior you want.

function example_function(src,event)
    
if ~ismember(event.Value,src.ItemsData)
    Items = src.Items;
    Items{event.PreviousValue} = event.Value;
    src.Items = Items;
end
end

[Jonas Schütz]

I also thought about a similar way to do it but the problem is after the first edit, event.PreviousValue will change to a string. I believe there is no way to achieve the behavior I want

[Cris LaPierre]

Have you tested the code I shared? Seems to work for me, but perhaps I don't fully understand the issue you are trying to describe.

[Jonas Schütz]

Sorry, it is indeed working as described. Thank you very very much! I wasn't at the PC and only had seen the

event.PreviousValue

with which I also had played around a bit. Thank you! I only had tested event.PreviousValue without ItemsData property but with the ItemsData property it behaves like expected.