While switching focus between Swing components, FOCUS_LOST and FOCUS_GAINED events are generated as expected. However, for all FOCUS_LOST events, the getOppositeComponent() method always returns null and it is not possible to determine the component that gained focus.

This behavior (for Swing GUI Components) happens on all platforms:
- Solaris, Solaris IA, Win98 and Linux

This bug was found with new Focus Test Suite test:
Swing/OppositeComponentTest/

Tested with build:
- jdk1.4 Build40

Sample code to reproduce bug (after GUI comes up just click on any of the components and observe the focus events generated):

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

public class OppositeComponentSample extends Frame implements FocusListener {

JTextField textfield;
JList list;
JPanel testpanel;

Component focusLost=null;
Component focusGained=null;

public OppositeComponentSample() {

testpanel = new JPanel();
textfield = new JTextField("TexField");
textfield.setName("JTEXTFIELD");
textfield.addFocusListener(this);

String items[] = {"Item 1","Item 2","Item 3","Item 4","Item 5"};
list = new JList(items);
list.setName("JLIST");
list.addFocusListener(this);

testpanel.add(textfield);
testpanel.add(list);
testpanel.setBackground(Color.yellow);

add(testpanel);
setSize(300,100);
setVisible(true);
}

public void focusLost(FocusEvent fe) {
System.out.println("\n** focusLost Method" );
focusGained = fe.getOppositeComponent();
if (focusGained == null) {
System.out.println("** Warning: getOppositeComponent() is null");
}
System.out.println(fe);
}

public void focusGained(FocusEvent fe) {
            System.out.println("\n** focusGained Method");
            focusLost = fe.getOppositeComponent();
            if (focusLost == null) {
System.out.println("** Warning: getOppositeComponent() is null");
}
            System.out.println(fe);
}

    public static void main(String args[]) {
        
        OppositeComponentSample opc=new OppositeComponentSample();
    }
}