Mixed alignment with Java Swing's GroupLayout

I'm trying to build a GUI window in my application. What I'm trying to do is have a window, with a few buttons at the top, and a large text area. Something like this:

+--------------------------------------------------+
| [button1] [button2]                    [button3] |
| +----------------------------------------------+ |
| | text area                                    | |
| |                         开发者_如何学Go                     | |
| |                                              | |
| |                                              | |
| +----------------------------------------------+ |
+--------------------------------------------------+

I'm almost there, using GroupLayout:

  layout.setHorizontalGroup(
    layout.createParallelGroup()
      .addGroup(layout.createSequentialGroup()
        .addComponent(button1)
        .addComponent(button2))
        .addComponent(closeWindow))
      .addComponent(textarea1)
  );

  layout.setVerticalGroup(
    layout.createSequentialGroup()
      .addGroup(layout.createParallelGroup()
        .addComponent(button1)
        .addComponent(button2)
        .addComponent(button3))
      .addComponent(textarea)
  );

The problem is that this ends up with button3 aligned to the left, with the other two. I can't seem to figure out how I can specify the alignment on just that one button. I can do GroupLayout.Alignment.TRAILING on the entire button bar, but that hits all 3 buttons, which is also not quite right.

So what's the correct approach? Since the alignment only applies for Parallel Groups, I don't think having a HorizontalGroup with two Sequential Groups in it will help?

What am I missing?

Add a gap in your sequential group. Leaving your horizontal group as is:

layout.setVerticalGroup(
    layout.createSequentialGroup()
      .addGroup(layout.createParallelGroup()
        .addComponent(button1)
        .addComponent(button2)
        .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        .addComponent(button3))
      .addComponent(textarea)
  );

The gap with those paramters acts as a "spring", taking up all available space.

Try adding:

.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 1, Short.MAX_VALUE)

after the second button. The MAX_VALUE will cause the gap to expand as much as necessary.

You want to use addPreferredGap() which is only available on sequential groups. The code below gives you the desired layout.

    layout.setHorizontalGroup(
            layout.createParallelGroup()
                    .addGroup( layout.createSequentialGroup()
                            .addComponent( button1 )
                            .addComponent( button2 )
                            .addPreferredGap( LayoutStyle.ComponentPlacement.RELATED, GroupLayout.PREFERRED_SIZE, Short.MAX_VALUE )
                            .addComponent( button3 ) )
                    .addComponent( textArea )
    );
    layout.setVerticalGroup(
            layout.createSequentialGroup()
                    .addGroup( layout.createParallelGroup()
                            .addComponent( button1 )
                            .addComponent( button2 )
                            .addComponent( button3 ) )
                    .addComponent( textArea )
    );