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package java.awt.event;

import java.util.EventListener;

The listener interface for receiving WindowEvents, including WINDOW_GAINED_FOCUS and WINDOW_LOST_FOCUS events. The class that is interested in processing a WindowEvent either implements this interface (and all the methods it contains) or extends the abstract WindowAdapter class (overriding only the methods of interest). The listener object created from that class is then registered with a Window using the Window's addWindowFocusListener method. When the Window's status changes by virtue of it being opened, closed, activated, deactivated, iconified, or deiconified, or by focus being transferred into or out of the Window, the relevant method in the listener object is invoked, and the WindowEvent is passed to it. 
Author:
David Mendenhall
See Also:
WindowAdapter
WindowEvent
Tutorial: Writing a Window Listener
Since:
1.4/**
 * The listener interface for receiving {@code WindowEvents}, including
 * {@code WINDOW_GAINED_FOCUS} and {@code WINDOW_LOST_FOCUS} events.
 * The class that is interested in processing a {@code WindowEvent}
 * either implements this interface (and
 * all the methods it contains) or extends the abstract
 * {@code WindowAdapter} class (overriding only the methods of interest).
 * The listener object created from that class is then registered with a
 * {@code Window}
 * using the {@code Window}'s {@code addWindowFocusListener} method.
 * When the {@code Window}'s
 * status changes by virtue of it being opened, closed, activated, deactivated,
 * iconified, or deiconified, or by focus being transferred into or out of the
 * {@code Window}, the relevant method in the listener object is invoked,
 * and the {@code WindowEvent} is passed to it.
 *
 * @author David Mendenhall
 *
 * @see WindowAdapter
 * @see WindowEvent
 * @see <a href="http://docs.oracle.com/javase/tutorial/uiswing/events/windowlistener.html">Tutorial: Writing a Window Listener</a>
 *
 * @since 1.4
 */
public interface WindowFocusListener extends EventListener {

    
Invoked when the Window is set to be the focused Window, which means
that the Window, or one of its subcomponents, will receive keyboard
events.
Params:
e – the event to be processed/**
     * Invoked when the Window is set to be the focused Window, which means
     * that the Window, or one of its subcomponents, will receive keyboard
     * events.
     * @param e the event to be processed
     */
    public void windowGainedFocus(WindowEvent e);

    
Invoked when the Window is no longer the focused Window, which means
that keyboard events will no longer be delivered to the Window or any of
its subcomponents.
Params:
e – the event to be processed/**
     * Invoked when the Window is no longer the focused Window, which means
     * that keyboard events will no longer be delivered to the Window or any of
     * its subcomponents.
     * @param e the event to be processed
     */
    public void windowLostFocus(WindowEvent e);
}