Animation in Applet

• Override the paint() method: The paint() method is called whenever the applet needs to be redrawn. You can override this method to draw the objects that you want to animate.
• Update the position of the objects: In the paint() method, update the position of the objects that you want to animate. This can be done using mathematical formulas or other algorithms.
• Call the repaint() method: After updating the position of the objects, call the repaint() method. This will trigger another call to the paint() method, allowing you to redraw the objects in their new positions.
• Use a java.util.Timer or java.util.ScheduledThreadPoolExecutor: To control the speed of the animation, you can use a java.util.Timer or java.util.ScheduledThreadPoolExecutor to schedule calls to the repaint() method at a specified interval.

Simple example of Applet by html file

import java.awt.*;
import java.applet.*;
import java.util.Timer;
import java.util.TimerTask;

public class BouncingBallApplet extends Applet {
  int x, y;
  int dx = 5, dy = 5;
  
  public void init() {
    setBackground(Color.WHITE);
    x = 0;
    y = 50;
    Timer timer = new Timer();
    timer.schedule(new TimerTask() {
      public void run() {
        x += dx;
        y += dy;
        if (x > getWidth() - 50 || x < 0)
          dx = -dx;
        if (y > getHeight() - 50 || y < 0)
          dy = -dy;
        repaint();
      }
    }, 0, 50);
  }

  public void paint(Graphics g) {
    g.setColor(Color.RED);
    g.fillOval(x, y, 50, 50);
  }
}

• In this example, the run() method is called at predetermined intervals of 50 milliseconds using a java.util.Timer. The paint() method is called after the run() method, which updates the position of the ball and calls the repaint() method, to redraw the ball in its new location.


• This is merely a straightforward illustration of the fundamental idea of animation in Java applets. Additional graphical primitives, such as lines, shapes, and images, as well as more complex algorithms to update the positions of the objects, can be used to make animations that are more complex.