Java Reference
In-Depth Information
As an anonymous listener is responsible for only a single button, it gets in-
formed only when this specific button is pressed. There is no need to check which
button it was. Therefore, we can immediately call methods increment and decre-
ment for the Up respectively Down button. For other listeners, however, there still
can be different events being triggered by the same component, e.g. for a mouse
listener, one might have to check which mouse button has been used. The use of
anonymous listeners is demonstrated in class CounterAnonymousPanel .
File: its/CounterAnonymousGUI/CounterAnonymousPanel.java
1. package its.CounterAnonymousGUI;
2.
3. import java.awt.BorderLayout;
4. import java.awt.event.ActionEvent;
5. import java.awt.event.ActionListener;
6. import javax.swing.*;
7.
8. public class CounterAnonymousPanel extends JPanel{
9.
10.
private CounterModel counter;
11.
private JLabel valueLabel;
12.
13.
public CounterAnonymousPanel() {
14.
counter = new CounterModel();
15.
16.
BorderLayout bordLay = new BorderLayout();
17.
this .setLayout(bordLay);
18.
19.
JButton upButton
= new JButton("Up");
20.
JButton downButton = new JButton("Down");
21.
valueLabel = new JLabel(""+counter.getValue(),SwingConstants.CENTER);
22.
23.
this .add(upButton,BorderLayout.WEST);
24.
this .add(downButton,BorderLayout.EAST);
25.
this .add(valueLabel,BorderLayout.CENTER);
26.
27.
// The listener for the up-button is defined
28.
// anonymous and on the fly.
29.
upButton.addActionListener( new ActionListener(){
30.
public void actionPerformed(ActionEvent evt){
31.
increment();
32.
}// actionPerformed
33.
}// ActionListener
34.
);// addActionListener
35.
36.
// The listener for the down-button is defined
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