The basic answer is "yes".
This assumes that the component you are trying to repaint is
- Added to a container
- That container is attached to some kind of native peer (ie a window)
- That window is visible.
The RepaintManager
is generally smart enough to know not to waste time painting something that isn't displayable.
The following example is rather basic, but will increment a counter within the paintComponent
of a JPanel
each time it is called. The Runnable
, which is attached to a Thread
, will update every second...
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class RepaintTest {
public static void main(String[] args) {
new RepaintTest();
}
public RepaintTest() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
TestPane tp = new TestPane();
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(tp);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
Thread thread = new Thread(new Repainter(tp));
thread.setDaemon(true);
thread.start();
}
});
}
public class Repainter implements Runnable {
private JPanel panel;
public Repainter(JPanel panel) {
this.panel = panel;
}
@Override
public void run() {
while (true) {
try {
Thread.sleep(1000);
} catch (InterruptedException ex) {
}
panel.repaint();
}
}
}
public class TestPane extends JPanel {
private int repaints = 0;
public TestPane() {
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics g2d = (Graphics2D) g.create();
repaints++;
FontMetrics fm = g2d.getFontMetrics();
String text = Integer.toString(repaints);
int x = (getWidth() - fm.stringWidth(text)) / 2;
int y = ((getHeight() - fm.getHeight()) / 2) + fm.getAscent();
g2d.drawString(text, x, y);
g2d.dispose();
}
}
}