I inspired by MeBigFatGuy interesting question, in this conection I have very specific question about Graphisc2D, how to change BackGround Color by depends if is JTables Row visible in the JViewPort,
1) if 1st. & last JTables Row will be visible in the JViewPort, then BackGround would be colored to the Color.red
2) if 1st. & last JTables Row will not be visible in the JViewPort, then BackGround would be colored to the Color.whatever
from SSCCE
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.RepaintManager;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.table.TableModel;
/*
https://stackoverflow.com/questions/1249278/
how-to-disable-the-default-painting-behaviour-of-wheel-scroll-event-on-jscrollpan
*
and
*
https://stackoverflow.com/questions/8195959/
swing-jtable-event-when-row-is-visible-or-when-scrolled-to-the-bottom
*/
public class ViewPortFlickering {
private JFrame frame = new JFrame("Table");
private JViewport viewport = new JViewport();
private Rectangle RECT = new Rectangle();
private Rectangle RECT1 = new Rectangle();
private JTable table = new JTable(50, 3);
private javax.swing.Timer timer;
private int count = 0;
public ViewPortFlickering() {
GradientViewPort tableViewPort = new GradientViewPort(table);
viewport = tableViewPort.getViewport();
viewport.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent e) {
RECT = table.getCellRect(0, 0, true);
RECT1 = table.getCellRect(table.getRowCount() - 1, 0, true);
Rectangle viewRect = viewport.getViewRect();
if (viewRect.intersects(RECT)) {
System.out.println("Visible RECT -> " + RECT);
} else if (viewRect.intersects(RECT1)) {
System.out.println("Visible RECT1 -> " + RECT1);
} else {
//
}
}
});
frame.add(tableViewPort);
frame.setPreferredSize(new Dimension(600, 300));
frame.pack();
frame.setLocation(50, 100);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
RepaintManager.setCurrentManager(new RepaintManager() {
@Override
public void addDirtyRegion(JComponent c, int x, int y, int w, int h) {
Container con = c.getParent();
while (con instanceof JComponent) {
if (!con.isVisible()) {
return;
}
if (con instanceof GradientViewPort) {
c = (JComponent) con;
x = 0;
y = 0;
w = con.getWidth();
h = con.getHeight();
}
con = con.getParent();
}
super.addDirtyRegion(c, x, y, w, h);
}
});
frame.setVisible(true);
start();
}
private void start() {
timer = new javax.swing.Timer(100, updateCol());
timer.start();
}
public Action updateCol() {
return new AbstractAction("text load action") {
private static final long serialVersionUID = 1L;
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("updating row " + (count + 1));
TableModel model = table.getModel();
int cols = model.getColumnCount();
int row = 0;
for (int j = 0; j < cols; j++) {
row = count;
table.changeSelection(row, 0, false, false);
timer.setDelay(100);
Object value = "row " + (count + 1) + " item " + (j + 1);
model.setValueAt(value, count, j);
}
count++;
if (count >= table.getRowCount()) {
timer.stop();
table.changeSelection(0, 0, false, false);
java.awt.EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
table.clearSelection();
}
});
}
}
};
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
ViewPortFlickering viewPortFlickering = new ViewPortFlickering();
}
});
}
}
class GradientViewPort extends JScrollPane {
private static final long serialVersionUID = 1L;
private final int h = 50;
private BufferedImage img = null;
private BufferedImage shadow = new BufferedImage(1, h, BufferedImage.TYPE_INT_ARGB);
private JViewport viewPort;
public GradientViewPort(JComponent com) {
super(com);
viewPort = this.getViewport();
viewPort.setScrollMode(JViewport.BLIT_SCROLL_MODE);
viewPort.setScrollMode(JViewport.BACKINGSTORE_SCROLL_MODE);
viewPort.setScrollMode(JViewport.SIMPLE_SCROLL_MODE);
Graphics2D g2 = shadow.createGraphics();
g2.setPaint(new Color(250, 150, 150));
g2.fillRect(0, 0, 1, h);
g2.setComposite(AlphaComposite.DstIn);
g2.setPaint(new GradientPaint(0, 0, new Color(0, 0, 0, 0f), 0, h,
new Color(0.5f, 0.8f, 0.8f, 0.5f)));
g2.fillRect(0, 0, 1, h);
g2.dispose();
}
@Override
public void paint(Graphics g) {
if (img == null || img.getWidth() != getWidth() || img.getHeight() != getHeight()) {
img = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
}
Graphics2D g2 = img.createGraphics();
super.paint(g2);
Rectangle bounds = getViewport().getVisibleRect();
g2.scale(bounds.getWidth(), -1);
int y = (getColumnHeader() == null) ? 0 : getColumnHeader().getHeight();
g2.drawImage(shadow, bounds.x, -bounds.y - y - h, null);
g2.scale(1, -1);
g2.drawImage(shadow, bounds.x, bounds.y + bounds.height - h + y, null);
g2.dispose();
g.drawImage(img, 0, 0, null);
}
}
since I search for different suggestion I closed this question with my original knowledges about Graphics
based on code