Re: Aligned elements in a JComboBox

Knute Johnson <>
Tue, 17 May 2011 18:00:29 -0700
On 05/17/2011 12:41 PM, Thomas Richter wrote:

On 17.05.2011 18:49, Knute Johnson wrote:

On 05/17/2011 09:42 AM, Thomas Richter wrote:

Hi folks,

the problem at hand is how to align individual components that are part
of a JComboBox.

The JComboBox uses a custom Renderer to render its contents, and each
content consists of two strings of variable size, arranged in a JPanel.
The getListCellRendererComponent() of the renderer now returns the
JPanel containing the two components.

So far, so good. This works.

The problem is that the sizes of the two components differ througout the
items of the JComboBox, which means that the elements within the JList
in the JCombobox (or rather, its JList rendering the non-editable items)
are not aligned to each other. Of course they can't, they are individual
JPanels each with its own layout manager, and thus do not know anything
on each other.

Needless to say, this looks visually very unattractive.

So what can I do about this? I have a JComboBox with a very complex
layout and the requirement that each entry necessarily is a pair of data
types of various sizes. How can I make the elements be aware of each
other and have a common layout for all of them?


| foofoo | barbarbarbarbarbarbarbar |
| foofoofoofoofoofoofoo | bar |

This is how the JComboBox currently renders. But I want it
laid out such that the separator between the two elements forming one
entry of it are underneath each other.

Any ideas?


Figure out the largest size of your data in each field and lay out all
the elements with the same width and layout manager.

Which layout manager accepts fixed widths for its components? If I use a
GridBagLayout, for example, changing the dimension of the components
within changes their alignment, and thus they'll move around even though
the layout manager stays the same.


You'll need one that follows preferred size or lay it out manually.
GridBagLayout won't work for sure. You can look back a few weeks and
there was a discussion about similar issue with text fields. Search for

'align Swing JLabels and JTextFields vertically with'

I did an example for the fellow with SpringLayout I think. I don't
think that would work here either but the idea is similar. GridLayout
would work if it would follow preferred or minimum size but I don't
think it will. You might consider extending that though or write your
own layout manager.


Knute Johnson

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