Java Reference
In-Depth Information
A timer generates timer events at fixed intervals.
When you use a timer, you specify the frequency of the events and an object of a
class that implements the ActionListener interface. Place whatever action you
want to occur inside the actionPerformed method. Finally, start the timer.
class MyListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
// This action will be executed at each timer event
Place listener action here
}
}
MyListener listener = new MyListener();
Timer t = new Timer (interval, listener);
t.start();
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Then the timer calls the actionPerformed method of the listener object
every interval milliseconds.
Our sample program will display a moving rectangle. We first supply a
RectangleComponent class with a moveBy method that moves the rectangle by
a given amount.
ch09/timer/RectangleComponent.java
1 import java.awt.Graphics;
2 import java.awt.Graphics2D;
3 import java.awt.Rectangle;
4 import javax.swing.JComponent;
5
6 /**
7 This component displays a rectangle that can be moved.
8 */
9 public class RectangleComponent extends
JComponent
10 {
11 public RectangleComponent()
12 {
13 // The rectangle that the paint method draws
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