JSplitPane: Panel from bottom component comes back in top component

Question

Hi,
In the next program I have added a small Panel (called smallPanel) to a Panel containing what I call a problem. The smallPanel is meant as a place holder for a checkbox that in my program is to be added when needed. So either the smallPanel is added, or a checkbox.
The smalLPanel is added to a panel in the bottomPanel. The bottomPanel is together with a topPanel added to a JSplitPane. What I found out is that if you scroll the bottomPanel downwards, the smallPanel shines through in the topPanel. My question is, is this a bug?
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class JSplitPaneProblem extends Canvas implements ActionListener
    static Color background;
    static String[] csdEngineers = {"jdoe1", "jdoe2", "jdoe3", "jdoe4", "jdoe5", "jdoet", "amacadam"};
    static String[] engineers = {"Choose one", "jdoe1", "jdoe2", "jdoe3", "jdoe4", "jdoe5", "jdoet", "amacadam"};
    static int width;
    static int height;
    static int remainingWidth;
    static int insets;
    static int labelWidth;
    static JScrollPane problemPane;
    static JPanel bottomPanel;
    static Panel smallPanel;
    static final int FAKE_CHECKBOX_SIZE = 10;
    static JSplitPane splitPane;
    static int BIGNUMBER = 100;
    public JSplitPaneProblem(JFrame frame)
        // Get the image to use.
        ImageIcon trafficLight = createImageIcon("any.gif");
        JLabel trafficLightLabel = new JLabel(trafficLight);
        if (trafficLight != null)
            width = trafficLight.getIconWidth();
            height = trafficLight.getIconHeight();
        else
            width = 100;
            height = 300;
        JPanel topPanel = new JPanel();
        JScrollPane trafficLightPane = new JScrollPane (ScrollPaneConstants.VERTICAL_SCROLLBAR_NEVER,
                    ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        trafficLightPane.setViewportView(topPanel);
        topPanel.setLayout(new BoxLayout(topPanel, BoxLayout.LINE_AXIS));
        for (int i = 0; i < BIGNUMBER; i++)
            trafficLight = createImageIcon("any.gif");
            trafficLightLabel = new JLabel(trafficLight);
            topPanel.add(trafficLightLabel);
        Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
        width = dimension.width;
        trafficLightPane.setPreferredSize(new Dimension(width, height));
        trafficLightPane.setMinimumSize(new Dimension(width, height+10)); // <-- Die doet ut
        height = 36;
        insets = 4; // Number of pixels to left and/or right of a component
        labelWidth = 40;
          frame.setBounds (0, 0, dimension.width, dimension.height);
        // And a new problem pane, to which the problem panel is added
        bottomPanel = new JPanel();
        bottomPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
        JScrollPane problemPane = new JScrollPane(ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
                    ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        problemPane.setViewportView(bottomPanel);
        // Set up the JSlitPane
        splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, trafficLightPane, problemPane);
        splitPane.setOneTouchExpandable(true);
        splitPane.resetToPreferredSizes();
        frame.add(splitPane);
     * The screen is divided in two equal sized halves, a left and a right side. Each half is divided into 3 parts.
     * remainingWidth is used to calculate the remaining width inside a half.
    public static JPanel addProblem(String organisation, String problem, int i)
        JPanel panel = new JPanel(); // JPanel has FlowLayout as default layout
        panel.setPreferredSize(new Dimension(width, height));
        // First half, containing serverId, customer name, and problem title
        // serverId
        JTextArea serverId = new JTextArea();
        if (i < 10)
            serverId.setText("9999" + i);
        else
            serverId.setText("999" + i);
        Font usedFont = new Font("SanSerif", Font.PLAIN, 12);
        serverId.setFont(usedFont);
        serverId.setPreferredSize(new Dimension(labelWidth, height));
        serverId.setBackground(background);
        panel.add(serverId);
        // Organisation name. Gets 1/3 of remaining width
        remainingWidth = (width / 2 - (int) serverId.getPreferredSize().getWidth()) / 3 - insets;
        JTextArea organisationArea = new JTextArea(organisation);
        organisationArea.setPreferredSize(new Dimension(remainingWidth, height));
        organisationArea.setAlignmentX(SwingConstants.LEFT);
        organisationArea.setBackground(background);
        organisationArea.setLineWrap(true);
        organisationArea.setWrapStyleWord(true);
        organisationArea.setEditable(false);
        panel.add(organisationArea);
        // Problem title
        JTextArea problemArea = new JTextArea(problem);
        problemArea.setPreferredSize(new Dimension(remainingWidth * 2, height));
        problemArea.setBackground(background);
        problemArea.setLineWrap(true);
        problemArea.setWrapStyleWord(true);
        problemArea.setEditable(false);
        panel.add(problemArea);
        // Second half, containing severity, CSD and Engineer
        // Severity
        JTextArea severity = new JTextArea("WARN");
        severity.setFont(usedFont);
        severity.setBackground(background);
        severity.setPreferredSize(new Dimension(labelWidth, height));
        panel.add(severity);
        // CSD
        JLabel csdField = new JLabel("CSD:");
        csdField.setFont(usedFont);
        JComboBox csdList = new JComboBox(csdEngineers);
        csdList.setFont(usedFont);
        csdList.setSelectedIndex(6);
        //csdList.addActionListener(this);
        panel.add(csdField);
        panel.add(csdList);
// Add "invisible" panel, used instead of checkbox (which is not added in this example)
        smallPanel = new Panel();
        smallPanel.setPreferredSize(new Dimension (FAKE_CHECKBOX_SIZE,
                    FAKE_CHECKBOX_SIZE));
        panel.add(smallPanel);
        // Solver, another ComboBox
        JLabel engineerField = new JLabel("Solver:");
        engineerField.setFont(usedFont);
        JComboBox engineerList = new JComboBox(engineers);
        engineerList.setFont(usedFont);
        engineerList.setSelectedIndex(0);
        //engineerList.addActionListener(this);
        panel.add(engineerField);
        panel.add(engineerList);
        // Empty panel to be added after this panel
        JPanel emptyPanel = new JPanel();
        emptyPanel.setPreferredSize(new Dimension(width, 15));
        return panel;
     * ActionListener
     * @param args
    public void actionPerformed(ActionEvent event)
        System.out.println("Burp");
    private static ImageIcon createImageIcon(String path)
        java.net.URL imgURL = JSplitPaneProblem.class.getResource(path);
        if (imgURL != null)
            return new ImageIcon(imgURL);
        else
            System.err.println("Couldn't find file: " + path);
            return null;
    private static void createAndShowGUI()
         Vector myVector = new Vector();
        // Create and set up the window.
        JFrame frame = new JFrame("JSlitPaneProblem");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        // Set the size of the window so in covers the whole screen
        Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setBounds(0, 0, dimension.width, dimension.height);
        // Create and set up the content pane.
        JSplitPaneProblem newContentPane = new JSplitPaneProblem(frame);       
        // Add panels to vector
        bottomPanel.setPreferredSize(new Dimension(dimension.width, dimension.height - height));
        for (int i = 0; i < BIGNUMBER; i++)
            myVector
                .add(addProblem(
                    "Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch Computer Shop",
                    "expected string or buffer, but that is not everyting, as this problem description is extremely long. And as I am chatty, I add some more length",
                    i));
            myVector.add(addProblem("My Company", "I have no problem", i));
        System.out.println ("adding problems to bottomPanel for the first time");
        for (int j = 0; j < 2 * BIGNUMBER; j++) {
             bottomPanel.add((JPanel)myVector.get(j));
        bottomPanel.removeAll();
        bottomPanel.revalidate();
        System.out.println ("adding problems to bottomPanel for the second time");
        for (int j = 0; j < 2 * BIGNUMBER; j++) {
             bottomPanel.add((JPanel)myVector.get(j));
        frame.setVisible(true);
        frame.pack();
    public static void main(String[] args)
        javax.swing.SwingUtilities.invokeLater(new Runnable()
            public void run()
                createAndShowGUI();
}If you need an image to try out this problem, you can find it here.
Abel
Edited by: Abel on 22-apr-2008 11:41
When you don't see anything in the topPanel, scroll it a bit to the right, and the bottomPanel upwards.

Answer 1

Use a JPanel, not a Panel, so you don't mix heavyweight and lightweight components.