Prentice.Hall.Introduction.to.Java.Programming,.Brief.Version.9th.(2014).[sharethefiles.com]

628 Chapter 16 Event-Driven Programming
clock display a new current time every second? The key to making the clock tick is to repaint
it every second with a new current time. You can use a timer to control the repainting of the
clock with the code in Listing 16.12.
VideoNote
Animate a clock
create a clock
create a timer
start timer
listener class
implement handler
set new time
repaint
LISTING 16.12
ClockAnimation.java
1 import java.awt.event.*;
2 import javax.swing.*;
3
4 public class ClockAnimation extends JFrame {
5 private StillClock clock = new StillClock();
6
7 public ClockAnimation() {
8 add(clock);
9
10 // Create a timer with delay 1000 ms
11 Timer timer = new Timer(1000, new TimerListener());
12 timer.start();
13 }
14
15 private class TimerListener implements ActionListener {
16 @Override /** Handle the action event */
17 public void actionPerformed(ActionEvent e) {
18 // Set new time and repaint the clock to display current time
19 clock.setCurrentTime();
20 clock.repaint();
21 }
22 }
23
24 /** Main method */
25 public static void main(String[] args) {
26 JFrame frame = new ClockAnimation();
27 frame.setTitle("ClockAnimation");
28 frame.setSize(200, 200);
29 frame.setLocationRelativeTo(null); // Center the frame
30 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
31 frame.setVisible(true);
32 }
33 }
The program displays a running clock, as shown in Figure 16.20. ClockAnimation
creates a StillClock (line 5). Line 11 creates a Timer for a ClockAnimation. The timer
is started in line 12. The timer fires an ActionEvent every second, and the listener responds
to set a new time (line 19) and repaint the clock (line 20). The setCurrentTime() method
defined in StillClock sets the current time in the clock.
FIGURE 16.20
A live clock is displayed in the panel.