Question

What is the easiest way in standard Java Swing to align three components in such a way that:

• the dynamic widths of Component1 and Component3 are adjusted to be equal,

• while Component2 (which is in between) has constant width?

Imagine we have some resizable JPanel (such as inside a JFrame).

Small width should look like this:

[----------------whole JPanel----------------]
[--Component1--] [Component2] [--Component3--]

Big width should look like this:

[------------------------whole JPanel------------------------]
[------Component1------] [Component2] [------Component3------]

Note: I just “trialed-and-errored” with GroupLayout for too long.

Answer 1

One option is using a GridBagLayout. A quick and dirty snippet to get you started:

GridBagConstraints gbc;
final int A_CENTER = GridBagConstraints.CENTER;  // anchor: center
final int F_NONE = GridBagConstraints.NONE;  // fill: none
final int F_DX = GridBagConstraints.HORIZONTAL;  // fill: dx only
final Insets IN_0 = new Insets(0, 0, 0, 0);  // empty insets

setLayout(new GridBagLayout() );
gbc = new GridBagConstraints(0, 0, 1, 1, 50.0, 0.0, A_CENTER, F_DX, IN_0, 0, 0);
add(new JButton("test1"), gbc);
gbc = new GridBagConstraints(1, 0, 1, 1, 0.0, 0.0, A_CENTER, F_NONE, IN_0, 0, 0);
add(new JButton("test2"), gbc);
gbc = new GridBagConstraints(2, 0, 1, 1, 50.0, 0.0, A_CENTER, F_DX, IN_0, 0, 0);
add(new JButton("test1"), gbc);

Obviously there’s a lot more you can do with a GridBag, and you’ll need to do some polishing to get exactly what you want to see, but this should get you started.

The fifth parameter in the GBC constructor is a weight for stretching in the x direction. Setting them equal, and forcing the center component not to stretch (F_NONE) does the dirty work.