ValueIndex of ListBox can not be set to 1

I created a 'Listbox' in AppDesigner

I can preset the selected items in the listbox by setting the value indices, for example

• app.ListBox.ValueIndex = [2 3]
• app.ListBox.ValueIndex = [3 2]

correctly preselects items with indices 2 and 3.

In addition, I can also select no item with

• app.ListBox.ValueIndex = []

The code works for all index value combinations, as long as I do not include index value equal to 1.

In other words, I can not set index value equal to 1, i.e.

• app.ListBox.ValueIndex = [1]
• app.ListBox.ValueIndex = [1 2]
• app.ListBox.ValueIndex = [1 2 3]

All give the error 'ValueIndex' must be [] or a 1-D vector of positive integers each representing an index in 'Items'.

Any idea what can be wrong here?

[Stephen23]

Odd. Please upload an MWE.

Are there any callbacks defined in the App?

[dpb]

"MWE" --> "minimum working example"

[dpb]

uilistbox -- the 'ValueIndex' propert was not introduced until R2023b -- mayhaps there's yet a bug as I notice that is the version you selected?

While I don't see that it should make any difference, try

app.ListBox.ValueIndex=1;

w/o the [];

[Bas van der Vorst]

Thanks for your feedback. Find some more information below.

A) Using app.ListBox.ValueIndex=1, i.e. when selecting a single item for the list the error seems to dissapear (see below). Howwver, the error remains when selecting more than one item from the list.

B) I will move to higher version to check if the error remains

C) MWE plus test results

Error message = 'ValueIndex' must be [] or a 1-D vector of positive integers each representing an index in 'Items'

I made the most simple example (only one line) to avoid any posibility of interference with other code parts but error remains

1) I made a listbox in GUI AppDesigner

2) Created listbox (default with 4 items)

3) Selected 'Multiselect' property to allow selection of more than 1 item from the list.

4) Created startupFnc with only one code line

app.ListBox.ValueIndex = [2 3 4];

This works fine.

5) I tested the following variants:

app.ListBox.ValueIndex = 1; % works fine, also for 2 3 and 4

app.ListBox.ValueIndex = [1]; % works fine, also for 2 3 and 4

app.ListBox.ValueIndex = [1 2]; % gives error

app.ListBox.ValueIndex = [1 2 3 4]; % gives error

app.ListBox.ValueIndex = [2 3 4]; % works fine

Seems selecting more than one item that includes itme with index 1 gives the error

classdef app1 < matlab.apps.AppBase
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure      matlab.ui.Figure
        ListBox       matlab.ui.control.ListBox
        ListBoxLabel  matlab.ui.control.Label
    end
    % Callbacks that handle component events
    methods (Access = private)
        % Code that executes after component creation
        function startupFcn(app)
            app.ListBox.ValueIndex = [2 3 4];
        end
    end
    % Component initialization
    methods (Access = private)
        % Create UIFigure and components
        function createComponents(app)
            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 640 480];
            app.UIFigure.Name = 'MATLAB App';
            % Create ListBoxLabel
            app.ListBoxLabel = uilabel(app.UIFigure);
            app.ListBoxLabel.HorizontalAlignment = 'right';
            app.ListBoxLabel.Position = [92 307 48 22];
            app.ListBoxLabel.Text = 'List Box';
            % Create ListBox
            app.ListBox = uilistbox(app.UIFigure);
            app.ListBox.Multiselect = 'on';
            app.ListBox.Position = [155 257 100 74];
            app.ListBox.Value = {'Item 1'};
            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end
    % App creation and deletion
    methods (Access = public)
        % Construct app
        function app = app1
            % Create UIFigure and components
            createComponents(app)
            % Register the app with App Designer
            registerApp(app, app.UIFigure)
            % Execute the startup function
            runStartupFcn(app, @startupFcn)
            if nargout == 0
                clear app
            end
        end
        % Code that executes before app deletion
        function delete(app)
            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end
end

[dpb]

That is the behavior as described by @Cris LaPierre in her answer. What I didn't recognize from the description is that any occurrence of "1" in the list errors; not just if only "1" is provided.

Owing to this, my suggested workaround doesn't work if the idea is to pick item 1 along with some others.

However, it's still pretty trivial to code; just use indirect addressing...

function startupFcn(app)
    iwant=[1 3];                                    % the list of wanted pre-selected items
    app.ListBox.Value=app.ListBox.Items(iwant);     % set the Value list by lookup into Items
end

Answer 1

[Cris LaPierre]

This appears to be a bug with ListBox in R2023b. When 'multiselect' is enabled, it throws the exception if the index is <=1 instead of <1.

This has been fixed in newer versions of MATLAB, but apparently the fix never made it back to R2023b.

The recommended workaround for now is to reference items by name instead of index. So assuming this is the listbox,

the corresponding code would be

app.ListBox.Value = {'Item 1'}
app.ListBox.Value = {'Item 1' 'Item 2'}
app.ListBox.Value = {'Item 1' 'Item 2' 'Item 3'}

I've shared a sample app.

[dpb]

Does the bug depend on the value == 1 or just one element in the case of 'MultiSelect'? If it's just for the specific value of "1", then the simpler fix is to rely on the default selection which is the first element which is simpler coding than matching the content/values (which is clearly why the enhancement was created).

[Cris LaPierre]

It is specifically when ValueIndex==1 is included in the list of indices to select. If you wanted to just select the 2nd item, this code would work without throwing the error: app.ListBox.ValueIndex = 2

[dpb]

@Thanks, Cris...I'm holding @ R2021b at present to continue to support an app on a system controlled by an IT group so couldn't check it out.

[Bas van der Vorst]

Dear Cris and dpb,

Thanks for your comments.

Just upgraded to MATLAB 24b and the above (very simple) code fully works now for all 'MultiSelect' combinations.

Indeed seems to be a bug in 2023b,

Kind regards,

Bas