What is the preferred layout manager for a container with collapsable JPanels

My code h开发者_如何学Pythonas a JPanel that contains three collapsible JPanels. The outer JPanel uses the BoxLayout to stack the three JPanels vertically. However, when I collapse a JPanel, the top JPanel will always expands to fill the region (even if I setMaximumSize() or such), whereas I want the lower JPanels to expand upward. It is generally glitchy. I was looking at the GridBagLayout, would that be more suitable for this sort of endeavor?

Thanks.

This is a VB image of what I dream about in my wildest dreams (images with title "Vertical Panels"):

http://www.codeproject.com/KB/cpp/CollapsiblePanelVB.aspx

I don't know what a collapsable panel is. Does it collapse all the way to 0, or does is have a minimum height?

If you manage the maximum size to always equal the preferred size then you should be able to use a BoxLayout. Just make sure you also use:

panel.add( Box.createVerticalGlue() );

at the bottom of your panel to allow the extra space to be used by the glue.

It would take me forever to cut out a compilable snippet from the 500 lines of garbage sprawled out before me.

And that is the reason for creating a SSCCE and forgetting about your garbage code. All you need is a panel with 3 collapsable panels. Then you add a button to collapse the panel and see what happens. Its better to start with demo code then write 500 lines of code and find out it doesn't work.

I strongly suggest MigLayout. It's very powerful and very easy to use. It's also widely used.

or old classic based on GridBagLayout

import java.awt.*;
import java.awt.event.*;
import java.awt.font.*;
import java.awt.image.BufferedImage;
import javax.swing.*;

public class ExpansiblePanel {

    public static void main(String[] args) {
        CollapsablePanel cp = new CollapsablePanel("test", buildPanel());
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new JScrollPane(cp));
        f.setPreferredSize(new Dimension(360, 200));
        f.setLocation(150, 150);
        f.pack();
        f.setVisible(true);
    }

    public static JPanel buildPanel() {
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(2, 1, 2, 1);
        gbc.weightx = 1.0;
        gbc.weighty = 1.0;
        JPanel p1 = new JPanel(new GridBagLayout());
        gbc.gridwidth = GridBagConstraints.RELATIVE;
        p1.add(new JButton("button 1"), gbc);
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        p1.add(new JButton("button 2"), gbc);
        gbc.gridwidth = GridBagConstraints.RELATIVE;
        p1.add(new JButton("button 3"), gbc);
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        p1.add(new JButton("button 4"), gbc);
        p1.setBackground(Color.blue);
        return p1;
    }

    private ExpansiblePanel() {
    }
}

class CollapsablePanel extends JPanel {

    private static final long serialVersionUID = 1L;
    private boolean selected;
    private JPanel contentPanel_;
    private HeaderPanel headerPanel_;

    private class HeaderPanel extends JPanel implements MouseListener {

        private static final long serialVersionUID = 1L;
        private String text_;
        private Font font;
        private BufferedImage open, closed;
        final int OFFSET = 30, PAD = 5;

        HeaderPanel(String text) {
            addMouseListener(this);
            text_ = text;
            font = new Font("sans-serif", Font.PLAIN + Font.BOLD, 12);
            // setRequestFocusEnabled(true);
            setPreferredSize(new Dimension(200, 25));
            setBackground(Color.black);
            setForeground(Color.red);
            int w = getWidth();
            int h = getHeight();
            /*try {
            open = ImageIO.read(new File("images/arrow_down_mini.png"));
            closed = ImageIO.read(new File("images/arrow_right_mini.png"));
            } catch (IOException e) {
            e.printStackTrace();
            }*/
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;
            g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            int h = getHeight();
            /*if (selected)
            g2.drawImage(open, PAD, 0, h, h, this);
            else
            g2.drawImage(closed, PAD, 0, h, h, this);
             */ // Uncomment once you have your own images
            g2.setFont(font);
            FontRenderContext frc = g2.getFontRenderContext();
            LineMetrics lm = font.getLineMetrics(text_, frc);
            float height = lm.getAscent() + lm.getDescent();
            float x = OFFSET;
            float y = (h + height) / 2 - lm.getDescent();
            g2.drawString(text_, x, y);
        }

        @Override
        public void mouseClicked(MouseEvent e) {
            toggleSelection();
        }

        @Override
        public void mouseEntered(MouseEvent e) {
        }

        @Override
        public void mouseExited(MouseEvent e) {
        }

        @Override
        public void mousePressed(MouseEvent e) {
        }

        @Override
        public void mouseReleased(MouseEvent e) {
        }
    }

    CollapsablePanel(String text, JPanel panel) {
        super(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(1, 3, 0, 3);
        gbc.weightx = 1.0;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        selected = false;
        headerPanel_ = new HeaderPanel(text);
        setBackground(Color.orange);
        contentPanel_ = panel;
        add(headerPanel_, gbc);
        add(contentPanel_, gbc);
        contentPanel_.setVisible(false);
        JLabel padding = new JLabel();
        gbc.weighty = 1.0;
        add(padding, gbc);
    }

    public void toggleSelection() {
        selected = !selected;
        if (contentPanel_.isShowing()) {
            contentPanel_.setVisible(false);
        } else {
            contentPanel_.setVisible(true);
        }
        revalidate();
        headerPanel_.repaint();
    }
}