Re: How do I paint on an existing Panel?

Sorry, I'm stumped, again. I really have been trying to sort it out
myself, but no luck. I've done it by adapting Knute Johnson's code
(which works fine in itself). Mine now defines a line and calls
repaint() as nice as you like, but there's no answer.

I've chopped the code back to just the bits directly involved with the
drawing and sprinkled debugging statements everywhere, which established
that the bit that calls paintComponent() (via repaint() - that's right
isn't it?) is firing but paintComponent() itself isn't. Here's what's
left, if you're interested. Sorry if anyone finds it hard to read, I
don't know how you like it formatted.

------------------------
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;

public class Vectorine extends JFrame implements MouseListener
{
private static final long serialVersionUID = 159L;
// List to contain all the lines generated
private final java.util.List<ColoredLine> lineList = new
java.util.ArrayList<ColoredLine>();

public static void main() {Vectorine v = new Vectorine();}

public Vectorine()
{
super("Vectorine");
setSize(200, 200);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);

// Set up window's initial contents
Container contentArea = getContentPane();
FlowLayout layout = new FlowLayout();
contentArea.setLayout(layout);
JPanel panelA = new JPanel();
panelA.addMouseListener(this);
contentArea.add(panelA);
setContentPane(contentArea);

System.out.println("If you click anywhere in the box, 3 random lines
should appear in it.");
}

public void paintComponent(Graphics g2d)
{
Graphics2D g = (Graphics2D)g2d;
System.out.println("Painting...");
for (ColoredLine hand : lineList)
{
System.out.println("Drawing line...");
BasicStroke pen = new BasicStroke(hand.getThickness());
g.setStroke(pen);
g.setColor(hand.getColor());
g.draw(hand);
}
}

public void mouseClicked(MouseEvent event)
{
System.out.println("Mouse clicked");
double xcoord = 0, ycoord = 0;
for (int count=0; count<3; count++)
{
xcoord = 100 * Math.random();
ycoord = 100 * Math.random();
System.out.println("xcoord="+xcoord+", ycoord="+ycoord);
ColoredLine hand = new ColoredLine(0F, 0F, (float)xcoord, (float)ycoord,
Color.red, 2);
lineList.add(hand);
System.out.println("Calling repaint()...");
repaint();
}
}

/** Blank methods to keep MouseListener happy. */
public void mousePressed(MouseEvent event) {}
public void mouseReleased(MouseEvent event) {}
public void mouseEntered(MouseEvent event) {}
public void mouseExited(MouseEvent event) {}
}

/** The actual lines drawn are instances of the ColoredLine class. */
class ColoredLine extends Line2D.Double
{ private static final long serialVersionUID = 149L;
private final Color color;
private final int thickness;
public ColoredLine(double x,double y,double w,double h,Color color,int
thickness)
{
super(x,y,w,h);
this.color = color;
this.thickness = thickness;
}

public Color getColor() {return color;}
public int getThickness() {return thickness;}
}