UsingFocusListener.java Source code

Introduction

Here is the source code for UsingFocusListener.java

Source

import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;

import javax.swing.JFrame;
import javax.swing.JTextField;

public class UsingFocusListener {

    public static void main(String[] a) {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JTextField textField = new JTextField("A TextField");
        textField.addFocusListener(new FocusListener() {
            public void focusGained(FocusEvent e) {
                displayMessage("Focus gained", e);
            }

            public void focusLost(FocusEvent e) {
                displayMessage("Focus lost", e);
            }

            void displayMessage(String prefix, FocusEvent e) {
                System.out.println(prefix + (e.isTemporary() ? " (temporary):" : ":")
                        + e.getComponent().getClass().getName() + "; Opposite component: "
                        + (e.getOppositeComponent() != null ? e.getOppositeComponent().getClass().getName()
                                : "null"));
            }

        });

        frame.add(textField, "North");
        frame.add(new JTextField(), "South");
        frame.setSize(300, 200);
        frame.setVisible(true);
    }

}