java - How to prevent Boxlayout/Box from stretching children components?

Question

As you can see in the runnable code below, i try to have a Box with expandable child-boxes. The children Boxes can change they size and this all works good. The main problem is that the size is always relative to the parent. But I want them to have a specific size and in case there is no place anymore use the JScrollPane. At the moment they shrink the other children-boxes only.

I tried Glue and Filler, but it didn't work. The glue just had no effect and the filler had the side effect to keep always some place at the (even when the ScrollPane is in action). That is pretty ugly to have there so much free space.

So, do you know a good way to prevent the Boxes from stretching the children?

Thank you in advance!

import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.border.TitledBorder;


public class ExpandableMenueDemo {
    Box allBoxes; 
    ExpandableMenueDemo(){
        allBoxes = Box.createVerticalBox();

        TitledBorder title;
        title = BorderFactory.createTitledBorder("Filter");
        allBoxes.setBorder(title);

        for (int i = 0 ;i<3;i++){
            //generate collapsable components
            SubBox b = new SubBox("SubBox"+i);
            allBoxes.add(b.getSwingBox());

        }
        allBoxes.add(Box.createVerticalGlue());
    }

    public Container getMenue(){
        return allBoxes;
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        ExpandableMenueDemo m = new ExpandableMenueDemo();
        Box mainBox = Box.createHorizontalBox();

        mainBox.add(new JScrollPane(m.getMenue()));
        mainBox.add(new JTable(20,5));

        frame.setContentPane(mainBox);
        frame.pack();
        frame.setVisible(true);
    }


    class SubBox{
        Box box;
        Box header; 
        String name; 
        JButton cBtn;
        boolean isCollapsed = true;
        JLabel headerLine; 

        SubBox(String name) {
            this.name= name;
            box = Box.createVerticalBox();

            headerLine = new JLabel(name+" () :");

            header= Box.createHorizontalBox();
            cBtn = new JButton("v");
            cBtn.addActionListener(new ActionListener(){

                @Override
                public void actionPerformed(ActionEvent arg0) {
                    if (isCollapsed)show();
                    else collapse();
                }
            });
            collapse();

            header.add(cBtn);
            header.add(Box.createHorizontalStrut(10));
            header.add(headerLine);
            header.add(Box.createHorizontalGlue());

        }

        Box getSwingBox() {
            Box b = Box.createVerticalBox();    
            b.add(header);
            b.add(box);
            return b;
        }

        public void collapse(){
            System.out.println("collapse");
            box.removeAll();
            this.isCollapsed=true;
            cBtn.setText("v");
        }

        public void show(){
            System.out.println("show");
            box.removeAll();
            this.isCollapsed=false;
            cBtn.setText("^");

            for (int i = 0; i<3;i++) { 
               Box b = Box.createHorizontalBox();
               b.add(Box.createHorizontalStrut(20));
               b.add(new JCheckBox("checkBox "+i));
               b.add(Box.createHorizontalGlue());
               box.add(b);
            }
        }
    }
}

Answer 1

BoxLayout can accepting setXxxSize,

maybe better example for expanding/collapsing JPanels nests another JComponents

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

public class ExpandingPanels extends MouseAdapter {

    private ActionPanel[] aps;
    private JPanel[] panels;

    public ExpandingPanels() {
        assembleActionPanels();
        assemblePanels();
    }

    @Override
    public void mousePressed(MouseEvent e) {
        ActionPanel ap = (ActionPanel) e.getSource();
        if (ap.target.contains(e.getPoint())) {
            ap.toggleSelection();
            togglePanelVisibility(ap);
        }
    }

    private void togglePanelVisibility(ActionPanel ap) {
        int index = getPanelIndex(ap);
        if (panels[index].isShowing()) {
            panels[index].setVisible(false);
        } else {
            panels[index].setVisible(true);
        }
        ap.getParent().validate();
    }

    private int getPanelIndex(ActionPanel ap) {
        for (int j = 0; j < aps.length; j++) {
            if (ap == aps[j]) {
                return j;
            }
        }
        return -1;
    }

    private void assembleActionPanels() {
        String[] ids = {"level 1", "level 2", "level 3", "level 4"};
        aps = new ActionPanel[ids.length];
        for (int j = 0; j < aps.length; j++) {
            aps[j] = new ActionPanel(ids[j], this);
        }
    }

    private void assemblePanels() {
        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);
        JPanel p2 = new JPanel(new GridBagLayout());
        gbc.gridwidth = 1;
        gbc.anchor = GridBagConstraints.EAST;
        p2.add(new JLabel("enter"), gbc);
        gbc.anchor = GridBagConstraints.WEST;
        p2.add(new JTextField(8), gbc);
        gbc.anchor = GridBagConstraints.CENTER;
        p2.add(new JButton("button 1"), gbc);
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        p2.add(new JButton("button 2"), gbc);
        JPanel p3 = new JPanel(new BorderLayout());
        JTextArea textArea = new JTextArea(8, 12);
        textArea.setLineWrap(true);
        p3.add(new JScrollPane(textArea));
        JPanel p4 = new JPanel(new GridBagLayout());
        addComponents(new JLabel("label 1"), new JTextField(12), p4, gbc);
        addComponents(new JLabel("label 2"), new JTextField(16), p4, gbc);
        gbc.gridwidth = 2;
        gbc.gridy = 2;
        p4.add(new JSlider(), gbc);
        gbc.gridy++;
        JPanel p5 = new JPanel(new GridBagLayout());
        p5.add(new JButton("button 1"), gbc);
        p5.add(new JButton("button 2"), gbc);
        p5.add(new JButton("button 3"), gbc);
        p5.add(new JButton("button 4"), gbc);
        gbc.weighty = 1.0;
        gbc.fill = GridBagConstraints.BOTH;
        p4.add(p5, gbc);
        panels = new JPanel[]{p1, p2, p3, p4};
    }

    private void addComponents(Component c1, Component c2, Container c, GridBagConstraints gbc) {
        gbc.anchor = GridBagConstraints.EAST;
        gbc.gridwidth = GridBagConstraints.RELATIVE;
        c.add(c1, gbc);
        gbc.anchor = GridBagConstraints.WEST;
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        c.add(c2, gbc);
        gbc.anchor = GridBagConstraints.CENTER;
    }

    private JPanel getComponent() {
        JPanel panel = new JPanel(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;
        for (int j = 0; j < aps.length; j++) {
            panel.add(aps[j], gbc);
            panel.add(panels[j], gbc);
            panels[j].setVisible(false);
        }
        JLabel padding = new JLabel();
        gbc.weighty = 1.0;
        panel.add(padding, gbc);
        return panel;
    }

    public static void main(String[] args) {
        Runnable doRun = new Runnable() {

            @Override
            public void run() {
                ExpandingPanels test = new ExpandingPanels();
                JFrame f = new JFrame();
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.getContentPane().add(new JScrollPane(test.getComponent()));
                f.setSize(360, 500);
                f.setLocation(200, 100);
                f.setVisible(true);
            }
        };
        SwingUtilities.invokeLater(doRun);
    }
}

class ActionPanel extends JPanel {

    private static final long serialVersionUID = 1L;
    private String text;
    private Font font;
    private boolean selected;
    private BufferedImage open, closed;
    public Rectangle target;
    final int OFFSET = 30,
            PAD = 5;

    ActionPanel(String text, MouseListener ml) {
        this.text = text;
        addMouseListener(ml);
        font = new Font("sans-serif", Font.PLAIN, 12);
        selected = false;
        setBackground(new Color(200, 200, 220));
        setPreferredSize(new Dimension(200, 20));
        setBorder(BorderFactory.createRaisedBevelBorder());
        setPreferredSize(new Dimension(200, 20));
        createImages();
        setRequestFocusEnabled(true);
    }

    public void toggleSelection() {
        selected = !selected;
        repaint();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        int w = getWidth();
        int h = getHeight();
        if (selected) {
            g2.drawImage(open, PAD, 0, this);
        } else {
            g2.drawImage(closed, PAD, 0, this);
        }
        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);
    }

    private void createImages() {
        int w = 20;
        int h = getPreferredSize().height;
        target = new Rectangle(2, 0, 20, 18);
        open = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = open.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setPaint(getBackground());
        g2.fillRect(0, 0, w, h);
        int[] x = {2, w / 2, 18};
        int[] y = {4, 15, 4};
        Polygon p = new Polygon(x, y, 3);
        g2.setPaint(Color.green.brighter());
        g2.fill(p);
        g2.setPaint(Color.blue.brighter());
        g2.draw(p);
        g2.dispose();
        closed = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        g2 = closed.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setPaint(getBackground());
        g2.fillRect(0, 0, w, h);
        x = new int[]{3, 13, 3};
        y = new int[]{4, h / 2, 16};
        p = new Polygon(x, y, 3);
        g2.setPaint(Color.red);
        g2.fill(p);
        g2.setPaint(Color.blue.brighter());
        g2.draw(p);
        g2.dispose();
    }
}