Tiled image in JScrollPane paint issues...

Question

Hello,
I'd like to have a JTable in a JScrollPane, where the area between the table and scrollpane borders
has a tiled and faded background.
I can achieve this by overriding paintComponent for either JScrollPane or JViewport:
public void paintComponent(final Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
  //paint a tiled image over background.
Rectangle2D tr = new Rectangle2D.Double(0,0, img.getWidth(), img.getHeight());
TexturePaint tp = new TexturePaint(img, tr);
  g2.setPaint(tp);
  g2.fillRect(0,0, getWidth(), getHeight());
   //paint a translucent fade over tiled background.
  GradientPaint gp = new GradientPaint(0,0, firstColor, 0, getHeight(), secondColor);
  g2.setPaint(gp);
  g2.fillRect(0,0, getWidth(), getHeight());
} When the scrollpane appears, the background looks great. But as the user scrolls, the background
gets corrupted - the newly uncovered areas have overlapping tiled images or no image at all. If the
scroll pane is resized, the background repaints correctly.
What is the correct way to implement this effect ? How should the code be corrected? ( I've tried subclassing JScrollPane and JViewport with the same results.)

Answer 1

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class TileScroll
    public static void main(String[] args)
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new JScrollPane(new TiledPanel()));
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
class TiledPanel extends JPanel
    TexturePaint texture;
    GradientPaint gradient;
    boolean firstTime;
    public TiledPanel()
        firstTime = true;
        addComponentListener(new ComponentAdapter()
            public void componentResized(ComponentEvent e)
                firstTime = true;
        GridBagLayout gridbag = new GridBagLayout();
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.weightx = 1.0;
        gbc.gridwidth = gbc.REMAINDER;
        JTable table = getTable();
        table.setRowHeight(30);
        JPanel header = new JPanel(gridbag);
        gbc.fill = gbc.BOTH;
        header.add(table.getTableHeader(), gbc);
        setLayout(gridbag);
        gbc.fill = gbc.HORIZONTAL;
        gbc.insets = new Insets(20,20,0,20);
        add(header, gbc);
        gbc.weighty = 1.0;
        gbc.fill = gbc.BOTH;
        gbc.insets = new Insets(0,20,20,20);
        add(table, gbc);
    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(firstTime)
            init(w,h);
        g2.setPaint(texture);
        g2.fillRect(0,0,w,h);
        g2.setPaint(gradient);
        g2.fillRect(0,0,w,h);
    private void init(int w, int h)
        int s = Math.min(w,h)/18;
        BufferedImage image = new BufferedImage(s, s, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = image.createGraphics();
        g2.setPaint(Color.red);
        g2.fillRect(0, 0, s, s);
        g2.setPaint(Color.blue);
        g2.fillRect(0, 0, s/2, s/2);
        g2.fillRect(s/2, s/2, s, s);
        g2.dispose();
        texture = new TexturePaint(image, new Rectangle2D.Double(0,0,s,s));
        gradient = new GradientPaint(new Point2D.Double(w,0),
                                     new Color(140,120,0,140),
                                     new Point2D.Double(0,h),
                                     new Color(0,150,0,140));
    private JTable getTable()
        String[] headers = {
            "column 1", "column 2", "column 3", "column 4"
        int cols = 4;
        int rows = 16;
        String[][] data = new String[rows][cols];
        for(int j = 0; j < rows; j++)
            for(int k = 0; k < cols; k++)
                data[j][k] = "item " + (j * cols + k + 1);
        return new JTable(data, headers);
}