//: DynamicEvents.java
// The new Java 1.1 event model allows you to
// change event behavior dynamically. Also
// demonstrates multiple actions for an event.
import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class DynamicEvents extends Frame {
Vector v = new Vector();
int i = 0;
Button
b1 = new Button("Button 1"),
b2 = new Button("Button 2");
public DynamicEvents() {
setLayout(new FlowLayout());
b1.addActionListener(new B());
b1.addActionListener(new B1());
b2.addActionListener(new B());
b2.addActionListener(new B2());
add(b1);
add(b2);
}
class B implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.out.println("A button was pressed");
}
}
class CountListener implements ActionListener {
int index;
public CountListener(int i) { index = i; }
public void actionPerformed(ActionEvent e) {
System.out.println(
"Counted Listener " + index);
}
}
class B1 implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.out.println("Button 1 pressed");
ActionListener a = new CountListener(i++);
v.addElement(a);
b2.addActionListener(a);
}
}
class B2 implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.out.println("Button 2 pressed");
int end = v.size() -1;
if(end >= 0) {
b2.removeActionListener(
(ActionListener)v.elementAt(end));
v.removeElementAt(end);
}
}
}
public static void main(String[] args) {
Frame f = new DynamicEvents();
f.addWindowListener(
new WindowAdapter() {
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
f.setSize(300,200);
f.show();
}
} ///:~
P.431
该例程中单击多次Button 1在Button 2上添加多个CountListener接收器后,单击Button 2一次,Button 2上的所有CountListener接收器都会列出来。
不知道为什么,求大神赐教!