Mega Code Archive
Animate a bouncing ball with Double Buffering
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import org.eclipse.swt.SWT;
import org.eclipse.swt.events.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;
public class AnimationDoubleBuffering {
private static final int IMAGE_WIDTH = 100;
private static final int TIMER_INTERVAL = 10;
private static int x = 0;
private static int y = 0;
private static int directionX = 1;
private static int directionY = 1;
private static Canvas canvas;
public static void animate() {
x += directionX;
y += directionY;
// Determine out of bounds
Rectangle rect = canvas.getClientArea();
if (x < 0) {
x = 0;
directionX = 1;
} else if (x > rect.width - IMAGE_WIDTH) {
x = rect.width - IMAGE_WIDTH;
directionX = -1;
}
if (y < 0) {
y = 0;
directionY = 1;
} else if (y > rect.height - IMAGE_WIDTH) {
y = rect.height - IMAGE_WIDTH;
directionY = -1;
}
// Force a redraw
canvas.redraw();
}
public static void main(String[] args) {
final Display display = new Display();
final Shell shell = new Shell(display);
shell.setText("Animator");
shell.setLayout(new FillLayout());
canvas = new Canvas(shell, SWT.NO_BACKGROUND);
canvas.addPaintListener(new PaintListener() {
public void paintControl(PaintEvent event) {
// Create the image to fill the canvas
Image image = new Image(shell.getDisplay(), canvas.getBounds());
// Set up the offscreen gc
GC gcImage = new GC(image);
gcImage.setBackground(event.gc.getBackground());
gcImage.fillRectangle(image.getBounds());
gcImage.setBackground(shell.getDisplay().getSystemColor(SWT.COLOR_RED));
gcImage.fillOval(x, y, IMAGE_WIDTH, IMAGE_WIDTH);
// Draw the offscreen buffer to the screen
event.gc.drawImage(image, 0, 0);
image.dispose();
gcImage.dispose();
}
});
shell.open();
Runnable runnable = new Runnable() {
public void run() {
animate();
display.timerExec(TIMER_INTERVAL, this);
}
};
display.timerExec(TIMER_INTERVAL, runnable);
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
// Kill the timer
display.timerExec(-1, runnable);
display.dispose();
}
}
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