Container events are fired after a component is added to or removed from the container.
import java.awt.event.ContainerEvent;
import java.awt.event.ContainerListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class UsingContainerListener {
public static void main(String[] a) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel buttonPanel = new JPanel();
buttonPanel.addContainerListener(new ContainerListener() {
public void componentAdded(ContainerEvent e) {
displayMessage(" added to ", e);
}
public void componentRemoved(ContainerEvent e) {
displayMessage(" removed from ", e);
}
void displayMessage(String action, ContainerEvent e) {
System.out.println(((JButton) e.getChild()).getText() + " was" + action
+ e.getContainer().getClass().getName());
}
});
buttonPanel.add(new JButton("A"));
frame.add(buttonPanel);
frame.setSize(300, 200);
frame.setVisible(true);
}
}