Java JApplet Graphics Double Buffering

Question

I'm writing a pretty simple game in Java, and I'm running into the issue of very serious flickering when I play the game as an applet in a browser. That is, all of my sprites, which are being painted on top of a background, are sometimes shown onscreen, but usually not - they repetitively flash onto the screen and then disappear. I've read that double buffering is probably the solution to this, but I'm having trouble implementing it correctly.

I'm using a JApplet as the container for a JPanel. This JPanel is the container onto which the sprites and game objects are painted - that is, in the JPanel's paintComonent method. In my JApplet, I'm using init, paint, and update override methods as follows:

Image offscreen;

Graphics bufferGraphics;

Dimension dim;

public void init(){
    dim = getSize();

    setBackground(Color.BLACK);

    offscreen = createImage(dim.width,dim.height);

    bufferGraphics = offscreen.getGraphics();

}

public void paint(Graphics g){
    bufferGraphics.clearRect(0,0,dim.width,dim.height);
    //here is my question - i"m not sure what I should print to bufferGraphics
    g.drawImage(offscreen, 0, 0, this);
}

public void update(Graphics g){
    paint(g);
}

The problem I'm running into is that, at the commented line, I'm unsure of what to do to get the current applet image printed to bufferGraphics. I read an example in which the sprite was painted straight to the JApplet, without using a JPanel. In light of that, my guess is that I'd need to paint the JPanel onto bufferGraphics at the commented line. Am I on the right track here? Any help is greatly appreciated; I just would like to know any way to do this properly.

Reformatted code, revert if incorrect. – Devon_C_Miller Mar 21 '11 at 16:37 — Devon_C_Miller, Mar 21 '11 at 16:37

score 2 · Answer 1 · answered Mar 20 '11 at 23:56

Swing is double buffered by default, there is no need to do anything special.

Your problem is probably the painting code. The code you posted is used for AWT painting, NOT Swing painting.

Custom painting is done by overriding the paintComponent() method of a JPanel or JComponent. I suggest you start by reading the Swing tutorial on Custom Painting for a working example.

Java JApplet Graphics Double Buffering

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