Editable combo-box

In previous articles, I explained how we can use findjobj to customize a Matlab uicontrol’s underlying Java control, thereby improving its appearance and functionality. My two previous articles on the Matlab editbox were a classic example of this mechanism. Unfortunately, this technique does not always work well, and an alternative mechanism needs to be used. One such case in point is the subject of today’s article.

Matlab combo-box (a.k.a. “popup-menu” or “drop-down”) controls are very simple controls that accept a list of strings from which a user can select. This is a very simple control that answers a wide range of use-cases. Unfortunately, it is quite limited. Among other limitations, we cannot modify the popup-panel’s appearance/functionality; we cannot select multiple items; and we cannot type-in a value in the control’s editbox. Today’s article will focus on the latter limitation, namely how to use an editable combo-box.

Trying to make Matlab’s standard combobox editable

We can indeed use findjobj to get a Matlab combo-box’s underlying Java control. This turns out to be a com.mathworks.hg.peer.ComboboxPeer$MLComboBox object, which extends the standard Java Swing JComboBox:

>> hCombo = uicontrol('Style','popup', 'String',{'a','b','c'});
>> jCombo = findjobj(hCombo)
jCombo =

This jCombo control has the Editable property that we can then try to override (the default value is false):

>> jCombo.setEditable(true);
>> jCombo.Editable = true;          % equivalent alternative
>> set(jCombo,'setEditable',true);  % equivalent alternative
Editable combo-box control

Editable combo-box control

The bad news is that the moment we enter some value (as in the screenshot here) that is not already a member of the pop-up panel (i.e., the cell-array in the String property), then the control disappears and a warning message is issued to the Matlab console:

Warning: popupmenu control requires that Value be an integer within String range
Control will not be rendered until all of its parameter values are valid
(Type "warning off MATLAB:hg:uicontrol:ParameterValuesMustBeValid" to suppress this warning.)

The reason for this behavior is that when the combo-box object detects that the text field’s content match none of the popup list items, it automatically sets jCombo‘s SelectedIndex to -1 and Matlab’s corresponding HG Value property to 0. At this point the Matlab implementation kicks in, hiding the uicontrol since it considers 0 an invalid value for the Value property. This is similar to the check being done to test for an empty HG String value (=no items):

>> set(hCombo, 'string', [])
popupmenu control requires a non-empty String
Control will not be rendered until all of its parameter values are valid.

We can clear these particular warnings via:


but this does not prevent the control from being hidden – it just prevents the warning from showing on the Command Window.

We can dive deeper and try to modify the underlying data model and disassociate the Java control from HG, but let’s stop at this point since there is really no point considering the fact that there is a much simpler alternative.

Note: if you do decide to make the standard Matlab uicontrol editable, read here for a related customization that I posted several years ago.

The pure-Java alternative

Rather than customizing Matlab’s uicontrol, we can easily create an identical-looking control using the standard Java Swing JComboBox, which has none of these problems/limitations. We can create and display the component in one go using the semi-documented javacomponent function:

position = [10,100,90,20];  % pixels
hContainer = gcf;  % can be any uipanel or figure handle
options = {'a','b','c'};
model = javax.swing.DefaultComboBoxModel(options);
jCombo = javacomponent('javax.swing.JComboBox', position, hContainer);jCombo.setModel(model);jCombo.setEditable(true);

We can use a variant of javacomponent to create the component with the model in one go, replacing the highlighted lines above:

jCombo = javacomponent({'javax.swing.JComboBox',model}, position, hContainer);

Once we have the control ready, all we need to do is set its ActionPerformedCallback property to our Matlab callback function and we’re pretty-much set. We can get the currently-selected text using char(jCombo.getSelectedItem) and the selected list index (0-based) using jCombo.getSelectedIndex (which returns -1 if we entered a non-listed value, 0 for the first list item, 1 for the second etc.). More information can be found here.

Lesson learnt

In the past 20+ years of my professional life as engineer and development manager, my number one rule has always been:


But sometimes, we should also remember an alternative version:

Available report – “Advanced Customizations of Matlab Uicontrols”

Interested readers can find more information about these and other possible customizations in my report on “Advanced Customizations of Matlab Uicontrols“. This 90-page PDF report can be purchased here ($39, please allow 24 hours for delivery by email). The report explains how to customize Matlab’s uicontrols in ways that are simply not possible using documented Matlab properties. This includes treatment of push buttons, toggle buttons, radio buttons, checkboxes, editboxes, listboxes, popup menus (aka combo-boxes/drop-downs), sliders, labels, and tooltips. Much of the information in the report is also available in hard-copy format in chapter 6 of my Matlab-Java programming book.

Categories: GUI, Java, Low risk of breaking in future versions, Semi-documented function, UI controls

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17 Responses to Editable combo-box

  1. moshe says:

    shalom Yair,
    first of all – I enjoy your fruitfull and interesting ideas
    second, regarding the editable combobox – is there a way to search the list as one types the words ‘online’ so he needs not scroll the whole list. i have a list of over 3000 to search…


    • Yair Altman says:

      @Moshe – you can either update the combo’s list items in the control’s KeyTypedCallback, or use a dedicated control that does it for you. One example is Matlab’s internal com.mathworks.widgets.AutoCompletionList, but this component does not exist in all Matlab releases.

      strs = {'This','is','test1','test2'};
      strList = java.util.ArrayList;
      for idx = 1 : length(strs),  strList.add(strs{idx});  end
      jPanelObj = com.mathworks.widgets.AutoCompletionList(strList,'');


      I explain this and other alternatives in pages 296-297 and 407-416 of my book.

    • moshe says:

      shalom Yair,
      as i struggle with the AutoCompletionList, a few questions are arised:
      1. how do i retrieve the value, string one chooses?
      2. can it be modified to look and behave like combobox?

      looking forward to hearing from you…

    • moshe says:

      another questions
      is there a way to search with wild cards and make the list shorter, as the user types the search?

    • @Moshe – I do not have additional information to what I wrote above and in my book. I’m afraid that you will need to investigate this by yourself for the time being, since I do not plan to write an article about this in the foreseeable future, sorry.

    • moshe says:

      I succeeded thanks to your suggestion to make use of the various optional Callbacks, when i’m done with the code i’ll be glad to publish it here

    • Steven Tsai says:

      Hi, Yair,
      “you can either update the combo’s list items in the control’s KeyTypedCallback”
      I tried set the jCombo’s KeyTypeCallback property, but it does not work:

      position = [10,100,90,20];  % pixels
      hContainer = gcf;  % can be any uipanel or figure handle
      options = {'a','b','c'};
      model = javax.swing.DefaultComboBoxModel(options);
      jCombo = javacomponent('javax.swing.JComboBox', position, hContainer);
      jComboh = handle(jCombo,'CallbackProperties');
      set(jComboh,'KeyTypedCallback','disp(''Hello, Yair'')')

      could you explain more details, thanks so much.

    • @Steven – You need to specify the KeyTypedCallback on the combo-box’es editbox (text-field) sub-component, not on the top-level component. Namely:

      jComboField = handle(jCombo.getComponent(jCombo.getComponentCount-1), 'CallbackProperties');
      set(jComboField, 'KeyTypedCallback', @myCallbackFunc);
  2. Steven Tsai says:

    Hi Yair,

    I was trying to use a ◾TreeComboBox in my GUI, but it seems something is wrong:

  3. King says:

    Hi Yair

    Firstly, thank you for your website.
    I found a lot of useful hints from your website.

    At this time, I try to call a MATLAB function when an item was selected in combo box’s drop down list. (mouse or up/down key pressed)
    I know I can do that in Java by adding ‘addactionlistener’ or ‘additemlistener’.

    How can I do the same job in MATLAB GUI?



    • @King –

      set(jCombo, 'ActionPerformedCallback', @myCallbackFcn)
    • King says:

      Thanks! It works!
      Before I saw your solution, I figure out I can use KeyReleasedCallBack as my callback property
      However, it still not solve the mouse click issue.
      Your one get the job done perfectly!
      Furthermore, instead of clicking mouse on the item, moving mouse on item then fire the callback?
      I tried jCombo.getcomponent(2) and added mouselistener, but it doesn’t help.
      Maybe I am in a right approach but missing some lines?


  4. King says:

    Hi Yair

    set(jCombo, ‘ActionPerformedCallback’, @myCallbackFcn)

    This commandline can handle the callback.
    But I want to handle the user input more precisely.
    I try to hear ‘Up’ ‘Down’ ‘Enter’key pressed or mouse left click.
    Therefore, I can assign different function to different user input.
    Is it possible to do that in combo box? If so, how?

    Thanks a lot.

  5. Buer says:

    Hi Yair,

    Thanks for the great information. However I want to ask if I have two combobox, how can I put them inside one figure instead of two?

    Meanwhile, if I want to have a label for each combbox. How can I do that? I checked around, did not find anything about that.


    • @Buer – you can use the Position property of the uicontrol to place it anywhere in your figure, and place separate uicontrols in separate locations. You can use other calls to uicontrol to place text labels. Look it up in the documentation.

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