miglayout: can't get right-alignment to work

Question

Something's not right here. I'm trying to get the rightmost button (labeled "help" in the example below) to be right-aligned to the JFrame, and the huge buttons to have their width tied to the JFrame but be at least 180px each. I got the huge button constraint to work, but not the right alignment.

I thought the right alignment was accomplished by gapbefore push (as in this other SO question), but I can't figure it out.

Can anyone help me?

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import net.miginfocom.swing.MigLayout;

public class RightAlignQuestion {
    public static void main(String[] args) {
        JFrame frame = new JFrame("right align question");
        JPanel mainPanel = new JPanel();
        frame.setContentPane(mainPanel);

        mainPanel.setLayout(new MigLayout("insets 0", "[grow]", ""));

        JPanel topPanel = new JPanel();
        topPanel.setLayout(new MigLayout("", "[][][][]", ""));
        for (int i = 0; i < 3; ++i)
            topPanel.add(new JButton("button"+i), "");
        topPanel.add(new JButton("help"), "gapbefore push, wrap");
        topPanel.add(new JButton("big button"), "span 3, grow");

        JPanel bottomPanel = new JPanel();
        bottomPanel.setLayout(new MigLayout("",
              "[180:180:,grow][180:180:,grow]","100:"));
        bottomPanel.add(new JButton("tweedledee"), "grow");
        bottomPanel.add(new JButton("tweedledum"), "grow");

        mainPanel.add(topPanel, "grow, wrap");
        mainPanel.add(bottomPanel, "grow");
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Answer 1

never mind, I got it: looks like there needs to be a gap constraint in the column spec, not at the component level:

    topPanel.setLayout(new MigLayout("", "[][][]push[]", ""));

Answer 2

a much easier/cleaner way (IMOH) is using component constraints and doing

topPanel.add(new JButton("help"), "push, al right, wrap");

Push will push the cell out as the window stretches but you need to tell the component to bind itself to the right of the cell. You could achieve the above with the following code.

    JPanel topPanel = new JPanel();
    frame.setContentPane(topPanel);

    for (int i = 0; i < 3; ++i)
        topPanel.add(new JButton("button"+i), "");
    topPanel.add(new JButton("help"), "push, al right, wrap");


    topPanel.add(new JButton("big button"), "span 3, grow, wrap");

    topPanel.add(new JButton("tweedledee"), "span, split2,grow, w 180, h 100");
    topPanel.add(new JButton("tweedledum"), "w 180, h 100, grow");