Drawing without paintComponent(Graphics g)

Question

Hi to all,
I use paintComponent(Graphics g) to draw particular rectangles on the screen, then i add some event to these rectangles. So far so good.I handle the mouse click from -->
public void mouseClicked(MouseEvent e){
// handling goes here
But an important part of my handling is to also draw something on the screen.
How can i do that from the mouseClicked method? Can i draw without using paintComponent(...)?
I mean that, once the paintComponent(...) method finishes, how can i still draw something on the screen?
Thanks,
John.

Answer 1

You can use
Graphics gg = component.getGraphics();
gg.draw ....
but it will be cleared in the paintComponent method
Look at this sample, the red rectangle will show up when the mouse
is presses, and gone when the mouse will be released.
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
public class Shapes extends JFrame
     DPanel pan = new DPanel();
public Shapes()
     addWindowListener(new WindowAdapter()
          public void windowClosing(WindowEvent ev)
               dispose();
               System.exit(0);
     setBounds(10,10,400,350); 
     setContentPane(pan);
     setVisible(true);
public class DPanel extends JPanel implements MouseListener
     Vector shapes = new Vector();
     Shape  cs;
public DPanel()
     addMouseListener(this);
     shapes.add(new Rectangle(20,20,100,40));
     shapes.add(new Rectangle(40,80,130,60));
     shapes.add(new Line2D.Double(20,150,200,180));
public void paintComponent(Graphics g)
     super.paintComponent(g);
     Graphics2D g2 = (Graphics2D)g;
     for (int j=0; j < shapes.size(); j++)
          g2.draw((Shape)shapes.get(j));
     g.setColor(Color.red);
     if (cs != null) g2.draw(cs);
public void mouseClicked(MouseEvent m) {}
public void mouseEntered(MouseEvent m) {}
public void mouseExited(MouseEvent m)  {}
public void mouseReleased(MouseEvent m)
     repaint();
public void mousePressed(MouseEvent m)
     for (int j=0; j < shapes.size(); j++)
          Shape s = (Shape)shapes.get(j);
          Rectangle r = new Rectangle(m.getX()-1,m.getY()-1,2,2);
          if (s.intersects(r))
               cs = s;
               Graphics g = getGraphics();
               g.setColor(Color.red);
               g.fillRect(r.x-5,r.y-5,10,10);
public static void main (String[] args) 
      new Shapes();
}