Issue with JScrollPane, JTextArea & JPanel

I need to add a vertical scroll bar to my JPanel. The issue arises when the long string of text doesn't wrap properly etc. So I followed steps online and put it in a text area and it worked fine (without scrollpane).

However upon adding the JScrollpane (which should only be vertical, and please assume that it is required i.e. can't set a minimum dimension) to the JPanel, when I resize it horizontally, it messes up completely. It doesn't wrap as it should upon resizing and the other components' positions mess up.

It may seem weird, that I have unnecessary panels here, however I'm working as part of a larger program and the are required (the for loop is just for testing purposes).

So to summarise: upon horizontal resizing the window, it doesn't behave as expected.

Would appreciate some guidance.

import java.awt.BorderLayout;
import java.awt.GridLayout;

import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.ScrollPaneConstants;

public class Main {

    public static void main(String[] args) {

        String s = "Hello my name is test. I am a test. Hello my name is test. I am a test. Hello my name is test. I am a test. Hello my name is test. I am a test. ";
        JFrame jf = new JFrame("Test");
        jf.setSize(600, 200);

        JPanel big = new JPanel();
        big.setLayout(new BoxLayout(big, BoxLayout.Y_AXIS));

        for (int i = 0; i < 2; i++) {
            JPanel first = new JPanel(new BorderLayout());

            JPanel insideTop = new JPanel(new GridLayout(2, 2));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));

            JPanel insideMiddle = new JPanel(new BorderLayout());
            insideMiddle.add(new JLabel("Description"), BorderLayout.NORTH);
            JTextArea jta = new JTextArea(s);
            jta.setWrapStyleWord(true);
            jta.setLineWrap(true);
            jta.setEditable(false);
            jta.setFocusable(false);
            jta.setOpaque(false);
            insideMiddle.add(jta, BorderLayout.CENTER);

            JPanel insideBottom = new JPanel(new BorderLayout());
            insideBottom.add(new JLabel("Bottom left"), BorderLayout.WEST);
            insideBottom.add(new JButton("Bottom right"), BorderLayout.EAST);

            first.add(insideTop, BorderLayout.NORTH);
            first.add(insideMiddle, BorderLayout.CENTER);
            first.add(insideBottom, BorderLayout.SOUTH);
            big.add(first);
        }

        JScrollPane scrollPane = new JScrollPane(big, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
                ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

        jf.add(scrollPane);
        jf.setVisible(true);

    }
}

Solution

Part of the problem is, once the component is allowed to expand, it doesn't want to shrink, so you need some way to constrain the component to always be the width of the viewable area.

Luckily, there is a relatively simple way to achieve it using the Scrollable interface...

public class BigPane extends JPanel implements Scrollable {

    @Override
    public Dimension getPreferredScrollableViewportSize() {
        return new Dimension(200, 200);
    }

    @Override
    public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction) {
        return 128;
    }

    @Override
    public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction) {
        return 128;
    }

    @Override
    public boolean getScrollableTracksViewportWidth() {
        return true;
    }

    @Override
    public boolean getScrollableTracksViewportHeight() {
        boolean track = true;
        Container parent = getParent();
        if (parent instanceof JViewport) {

            JViewport viewport = (JViewport) parent;
            if (viewport.getHeight() < getPreferredSize().height) {
                track = false;
            }

        }

        return track;
    }

}

What this basically does, is makes the component always honour the width of the JViewport, so when the JScrollPane/JViewport are performing their layouts, they know to constrain the width of the component to the width of the viewable area. Because I like it to work this way, when the component's preferred height is less than the viewable area, it will also fill the space, but you can make your own decisions about that...

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Rectangle;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JViewport;
import javax.swing.ScrollPaneConstants;
import javax.swing.Scrollable;

public class Main {

    public static void main(String[] args) {

        String s = "Hello my name is test. I am a test. Hello my name is test. I am a test. Hello my name is test. I am a test. Hello my name is test. I am a test. ";
        JFrame jf = new JFrame("Test");
        jf.setSize(600, 200);

        BigPane big = new BigPane();
        big.setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        gbc.weightx = 1;
        gbc.fill = GridBagConstraints.BOTH;

        for (int i = 0; i < 2; i++) {
            JPanel first = new JPanel(new BorderLayout());

            JPanel insideTop = new JPanel(new GridLayout(2, 2));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));

            JPanel insideMiddle = new JPanel(new BorderLayout());
            insideMiddle.add(new JLabel("Description"), BorderLayout.NORTH);
            JTextArea jta = new JTextArea(s);
            jta.setWrapStyleWord(true);
            jta.setLineWrap(true);
            jta.setEditable(false);
            jta.setFocusable(false);
            jta.setOpaque(false);
            insideMiddle.add(jta, BorderLayout.CENTER);

            JPanel insideBottom = new JPanel(new BorderLayout());
            insideBottom.add(new JLabel("Bottom left"), BorderLayout.WEST);
            insideBottom.add(new JButton("Bottom right"), BorderLayout.EAST);

            first.add(insideTop, BorderLayout.NORTH);
            first.add(insideMiddle, BorderLayout.CENTER);
            first.add(insideBottom, BorderLayout.SOUTH);
            big.add(first, gbc);
        }

        JScrollPane scrollPane = new JScrollPane(big, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
                ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

        jf.add(scrollPane);
        jf.setVisible(true);

    }

    public static class BigPane extends JPanel implements Scrollable {

        @Override
        public Dimension getPreferredScrollableViewportSize() {
            return new Dimension(200, 200);
        }

        @Override
        public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction) {
            return 128;
        }

        @Override
        public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction) {
            return 128;
        }

        @Override
        public boolean getScrollableTracksViewportWidth() {
            return true;
        }

        @Override
        public boolean getScrollableTracksViewportHeight() {
            boolean track = true;
            Container parent = getParent();
            if (parent instanceof JViewport) {

                JViewport viewport = (JViewport) parent;
                if (viewport.getHeight() < getPreferredSize().height) {
                    track = false;
                }

            }

            return track;
        }

    }
}

I also switched to a GridBagLayout, again, this is a personal choice, you might find that BoxLayout works okay for you