How to double-buffer a JWindow?

Question

Hi,
I made a resizable JWindow, but whenever I resize, J-components within the window flicker. (First setSize(), then validate() to redraw for correct sizes). I know JWindow is not double buffered, I want to override the paint() method to implement double buffering -- anyone knows how to do that? (...besides copying from JComponent.java)

Answer 1

I think double buffering available in Swing with out you doing anything. Just add the following line to your window initialization.
((JPanel)window.getContentPane()).setDoubleBuffered(true);If this doesn't work, and I think it should. Then use the code below.
This is code copied from http://java.sun.com/j2se/1.3/docs/guide/awt/designspec/lightweights.html
The following is a Panel, but you can apply the same logic to JWindow.
public class DoubleBufferPanel extends Panel {   
  Image offscreen;
   * null out the offscreen buffer as part of invalidation
  public void invalidate() {
      super.invalidate();
      offscreen = null;
   * override update to *not* erase the background before painting
  public void update(Graphics g) {
      paint(g);
   * paint children into an offscreen buffer, then blast entire image
   * at once.
  public void paint(Graphics g) {
      if(offscreen == null) {
         offscreen = createImage(getSize().width, getSize().height);
      Graphics og = offscreen.getGraphics();
      og.setClip(0,0,getSize().width, getSize().height);
      super.paint(og);
      g.drawImage(offscreen, 0, 0, null);
      og.dispose();