Re: JPanel to BufferedImage to JPanel problem
In article <hdmnmf$s12$1@nerdhammel.gnuher.de>,
Dario Ernst <usenet@nebuk.de> wrote:
[I]'m having quite some trouble with the following: I'm coding a
"game table" for a boardgame (mahjongg, not the solitaire variant but
the original poker-like game). The table has 4 players, one on each
side, so i have a panel with the discards, etc. on it that is in
front of each player - of course on the opposite side if the user its
rotated. So [I] thought [I]'d render it in a BufferedImage and rotate
the contents. Works so far - at least a bit.
My Problem's that [I] have some code in MahjongPanel that renders my
SeatPanels (containing the discards) to a BufferedImage and gives
this image to the corresponding PaintPanels (a custom panel with
overridden paint() method to draw its BufferedImage). Now [I]'d like
that code to run whenever swing decides it needs to repaint the
mahjongPanel. So [I] tried overriding its paint or paintComponent
method to also execute my renderSeat code.
Problem there is: I get tons of funny graphic effects such as the
whole MahjongPanel not being properly drawn over what was on my
MainFrame (code for that left out here for readability) before, only
partially drawn, etc.
What could that be? Any advice would be greatly appreciated!
Without a complete, compilable example or even a picture it's hard to
say. Several things stand out: 1) Be sure to construct your components
on the EDT [1]. 2) Custom drawing in Swing components should override
paintComponent, not paint(), and certainly not both. 3) The
Graphics context's transformations are concatenated, making some
operations hard to follow. I prefer to transform the object [2], but
it's not hard to save the initial transform and restore is as needed.
Resize to see the effect; see also [3]:
import java.awt.*;
import java.awt.geom.AffineTransform;
import javax.swing.*;
/** @author John B. Matthews */
public class RotateTest extends JPanel {
private static final Font f = new Font("Serif", Font.PLAIN, 20);
public RotateTest() {
setPreferredSize(new Dimension(300, 300));
}
@Override
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setFont(f);
g2d.setColor(Color.black);
g2d.fillRect(0, 0, getWidth(), getHeight());
String s = "Hello World!";
int xx = this.getWidth();
int yy = this.getHeight();
int w2 = g2d.getFontMetrics().stringWidth(s) / 2;
int h2 = g2d.getFontMetrics().getHeight();
AffineTransform original = g2d.getTransform();
g2d.setColor(Color.red);
g2d.drawString(s, xx / 2 - w2, yy - h2);
g2d.setColor(Color.green);
g2d.rotate(Math.PI / 2, h2, yy / 2 - w2);
g2d.drawString(s, h2, yy / 2 - w2);
g2d.setTransform(original);
g2d.setColor(Color.blue);
g2d.rotate(2 * Math.PI / 2, xx / 2 + w2, h2);
g2d.drawString(s, xx / 2 + w2, h2);
g2d.setTransform(original);
g2d.setColor(Color.lightGray);
g2d.rotate(3 * Math.PI / 2, xx - h2, yy / 2 + w2);
g2d.drawString(s, xx - h2, yy / 2 + w2);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(new RotateTest(), BorderLayout.CENTER);
f.pack();
f.setVisible(true);
}
});
}
}
[...]
[1]<http://java.sun.com/docs/books/tutorial/uiswing/concurrency/index.html>
[2]<http://sites.google.com/site/drjohnbmatthews/point-in-polygon>
[3]<http://tinypic.com/r/ezr982/4>
--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>