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

16.11 Animation Using the Timer Class 627
29
30 public MovingMessagePanel(String message) {
31 this.message = message;
32
33 // Start timer for animation
34 timer.start();
35
36 // Control animation speed using mouse buttons
37 this.addMouseListener(new MouseAdapter() {
38 @Override
39 public void mouseClicked(MouseEvent e) {
40 int delay = timer.getDelay();
41 if (e.getButton() == MouseEvent.BUTTON1)
42
43
timer.setDelay(delay > 10 ? delay - 10 : 0);
else if (e.getButton() == MouseEvent.BUTTON3)
44
45
timer.setDelay(delay < 50000 ? delay + 10 : 50000);
}
46 });
47 }
48
49 @Override /** Paint the message */
50 protected void paintComponent(Graphics g) {
51 super.paintComponent(g);
52
53 if (xCoordinate > getWidth()) {
54 xCoordinate = -20;
55 }
56 xCoordinate += 5;
57 g.drawString(message, xCoordinate, yCoordinate);
58 }
59
60
61
class TimerListener implements ActionListener {
@Override
62 public void actionPerformed(ActionEvent e) {
63 repaint();
64 }
65 }
66 }
67 }
set message
start timer
mouse listener
reset x-coordinate
move message
listener class
event handler
repaint
Two instances of MovingMessagePanel are created to display two messages (lines 9–10).
The MovingMessagePanel class extends JPanel to display a message (line 24). This class
is defined as an inner class inside the main class, because it is used only in this class. Furthermore,
the inner class is defined as static, because it does not reference any instance members
of the main class.
An inner class listener is defined in line 60 to listen for ActionEvent from a timer. Line
28 creates a Timer for the listener, and the timer is started in line 34. The timer fires an
ActionEvent every 1 second initially, and the listener responds in line 62 to repaint the
panel. When a panel is painted, its x-coordinate is increased (line 56), so the message is displayed
to the right. When the x-coordinate exceeds the bound of the panel, it is reset to -20
(line 54), so the message continues moving from left to right circularly.
A mouse listener is registered with the panel to listen for the mouse click event (lines
37–46). When the left mouse button is clicked, a new reduced delay time is set for the timer
(lines 41–42). When the right mouse button is clicked, a new increased delay time is set for
the timer (lines 43–44). The minimum delay time is 0 and the maximum can be
Integer.MAX_VALUE, but it is set to 50000 in this program (line 44).
In Section 13.9, Case Study: The StillClock Class, you drew a StillClock to show
the current time. The clock does not tick after it is displayed. What can you do to make the