Screen restoration after ALT+TAB

Question

Hi,
I'm writting an application with 2D graphics in the full-screen mode. If I press ALT+TAB to switch to another window and then another ALT+TAB to go back to my application, I can see only a white screen. I have no idea what is wrong. Here is my code.
GraphicsDevice graphicsDevice = GraphicsEnvironment
          .getLocalGraphicsEnvironment().getDefaultScreenDevice();
JFrame screen = new JFrame();
screen.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
screen.setIgnoreRepaint(true);
screen.setUndecorated(true);
screen.setResizable(false);
graphicsDevice.setFullScreenWindow(screen);
graphicsDevice.setDisplayMode(new DisplayMode(
          800, 600, 16, DisplayMode.REFRESH_RATE_UNKNOWN));
screen.createBufferStrategy(2);
BufferStrategy bufferStrategy = screen.getBufferStrategy();
while (!done) {
     if (bufferStrategy.contentsLost() && !bufferStrategy.contentsRestored()) {
          System.out.println("skip");
          continue;
     System.out.println("draw");
     Graphics graphics = bufferStrategy.getDrawGraphics();
     try {
          //render the screen
     } finally {
          graphics.dispose();
     bufferStrategy.show();
}After the second ALT+TAB bufferStrategy.contentsLost() is always true and bufferStrategy.contentsRestored() is always false. (i.e. I get only the "skip" debug message so the rendering commands are executed no more.)
Thanks for any help.

Answer 1

Hi,
Why do you have the whole '!bufferStrategy.contentsRestored()' part in 'if (bufferStrategy.contentsLost() && !bufferStrategy.contentsRestored())' at all? Wouldn't your code work without it and the screen would paint? I can't see why you would skip the paint if contentsRestored() is false.
Anyway, I use a VolatileImage to do the same thing as a BufferStrategy and it works in full screen mode or normal window mode. This is the code and it sits in a Canvas class:
     int currentWidth = 0;
     int currentHeight = 0;
     Graphics2D g2D = null;
    VolatileImage vImg = null;
    boolean hasBeenResized = false;
     public void reDisplay(Scenario scenario){
          if (hasBeenResized || vImg == null){
               System.out.println("hasBeenResized == true");
               currentWidth = getWidth();
               currentHeight = getHeight();
               vImg = createVolatileImage(currentWidth, currentHeight);
               hasBeenResized = false;
          g2D = (Graphics2D)getGraphics();
          do {
               renderOffscreen(scenario);
               int returnCode = vImg.validate(getGraphicsConfiguration());
               if (returnCode == VolatileImage.IMAGE_RESTORED) {
                    // Contents need to be restored
                    renderOffscreen(scenario);      // restore contents
               else if (returnCode == VolatileImage.IMAGE_INCOMPATIBLE) {
                    // old vImg doesn't work with new GraphicsConfig; re-create it
                    vImg = createVolatileImage(getWidth(), getHeight());
                    renderOffscreen(scenario);
               g2D.drawImage(vImg,0,0,this);
          } while (vImg.contentsLost());
          g2D.dispose();
     void renderOffscreen(Scenario scenario){
          do {
               if (vImg.validate(getGraphicsConfiguration()) == VolatileImage.IMAGE_INCOMPATIBLE){
                    // old vImg doesn't work with new GraphicsConfig; re-create it
                    vImg = createVolatileImage(currentWidth, currentHeight);
               Graphics2D g2D = vImg.createGraphics();
               render(scenario, g2D);
               g2D.dispose();
          } while (vImg.contentsLost());
     void render(Scenario scenario, Graphics2D g2D){
          // painting code here
     }I hope it helps,
Keith