Smooth animation

Question

hi there,
trying to achieve smooth animation, or graphics moving on screen without flickering blinking.
I checked some code samples here on Sun website and tried to use that technique to paint into off-screen image first and then just draw image on screen. I finished with something like this:
BufferedImage Sce;
public Graphics2D createGraphics2D(int w, int h) {
        Graphics2D g2 = null;
        if ( Sce == null || Sce.getWidth() != w || Sce.getHeight() != h ) {
            Sce = (BufferedImage) createImage(w,h);
        g2 = Sce.createGraphics();
        g2.setBackground(getBackground());
        g2.clearRect(0,0,w,h);
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
        return g2;
    public void somethingToDraw(Graphics2D a) {
              //bit of my code to draw shapes
    public void paint(Graphics g) {
        Dimension d = getSize();
        Graphics2D a = createGraphics2D(d.width, d.height);
        somethingToDraw(a);
        a.dispose();
        if ( Sce != null ) {
            g.drawImage(Sce, 0, 0, this);
}I think i copied almost everything as it was in the original sample, but it is flickering even more than in direct drawing. maybe i do mistake somewhere.
actually, scene is redrawn by method repaint(); which is called either in thread or on defined event.
should I refresh screen by repaint() or something else?

Answer 1

re-parent my drawing object to JPanel
Since Swing is double-buffered you can usually eliminate the offscreen (Sce) buffer.
I have not found any difference in flicker between Applet and application. AWT in either
form can have problems with flicker; (well-written) Swing does not. The main difference
between applets and applications is how you deal with applet/app context for
initialization/startup for things like loading images and calling start methods. It always
seems to take some tinkering to get things to work the way you want.
Here are a couple of suggestions for reducing flicker in AWT.
//  <applet code="AnimationTest" width="400" height="400"></applet>
//  ues: >appletviewer AnimationTest.java
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
public class AnimationTest extends Applet {
    Controller controller;
    public void init() {
        AnimationPanel ap = new AnimationPanel();
        controller = new Controller(ap);
        setLayout(new BorderLayout());
        add(ap);
    public void start() {
        controller.start();
    public void stop() {
        controller.stop();
    private static WindowListener closer = new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
            System.exit(0);
    public static void main(String[] args) {
        Applet applet = new AnimationTest();
        Frame f = new Frame();
        f.addWindowListener(closer);
        f.add(applet);
        f.setSize(400,400);
        f.setLocation(200,200);
        applet.init();
        f.setVisible(true);
        applet.start();
class AnimationPanel extends Canvas {
    BufferedImage image;
    Ellipse2D.Double ball;
    double radius;
    double theta;
    double thetaInc;
    public void paint(Graphics g) {
        if(image == null)
            initImage();
        g.drawImage(image, 0, 0, this);
     * omitting the call to super.update below avoids
     * clearing and repainting the whole background
     * with each call to repaint -> one way to reduce flicker
    public void update(Graphics g) {
        paint(g);
    public void advance() {
        // make certain image has been initialized
        if(image == null)
            return;
        // reposition the ball
        int w = getWidth();
        int h = getHeight();
        theta += thetaInc;
        ball.x = w/2 + radius*Math.cos(theta);
        ball.y = h/2 + radius*Math.sin(theta);
        // update image
        Graphics2D g2 = image.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setPaint(Color.white);
        g2.fillRect(0,0,w,h);
        g2.setPaint(Color.red);
        g2.fill(ball);
        g2.dispose();
        // repaint only the section that is changing
        // another way to reduce flicker
        repaint((int)ball.x-15, (int)ball.y-15, (int)ball.x+15, (int)ball.y+15);
    private void initImage() {
        int w = getWidth();
        int h = getHeight();
        radius = Math.min(w, h)/4.0;
        theta = 0;
        thetaInc = Math.toRadians(1);
        double x = w/2 + radius*Math.cos(theta);
        double y = h/2 + radius*Math.sin(theta);
        ball = new Ellipse2D.Double(x, y, 15, 15); // diameter = 15
        image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
                //getCompatibleImage(w, h);
        //System.out.printf("image = %s%n", image);
        Graphics2D g2 = image.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setPaint(Color.white);
        g2.fillRect(0,0,w,h);
        g2.setPaint(Color.red);
        g2.fill(ball);
        g2.dispose();
     * some operating systems do better with a compatible image
     * check the type of the BufferedImage returned by this method
     * most likely not be a factor in flicker-reduction
    private BufferedImage getCompatibleImage(int w, int h) {
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice gd = ge.getDefaultScreenDevice();
        GraphicsConfiguration gc = gd.getDefaultConfiguration();
        BufferedImage bestImage = gc.createCompatibleImage(w, h);
        return bestImage;
class Controller implements Runnable {
    AnimationPanel animationPanel;
    Thread thread;
    boolean animate;
    public Controller(AnimationPanel ap) {
        animationPanel = ap;
        animate = false;
    public void start() {
        if(!animate) {
            animate = true;
            thread = new Thread(this);
            thread.start();
    public void stop() {
        animate = false;
        thread.interrupt();
        thread = null;
    public void run() {
        while(animate) {
            try {
                Thread.sleep(40);
            } catch(InterruptedException ie) {
                System.out.println("Controller interrupted");
                stop();
            animationPanel.advance();
}