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package java.awt.event;

import java.util.EventListener;

The listener interface for receiving keyboard focus events on a component. The class that is interested in processing a focus event either implements this interface (and all the methods it contains) or extends the abstract FocusAdapter class (overriding only the methods of interest). The listener object created from that class is then registered with a component using the component's addFocusListener method. When the component gains or loses the keyboard focus, the relevant method in the listener object is invoked, and the FocusEvent is passed to it. 
Author:
Carl Quinn
See Also:
FocusAdapter
FocusEvent
Tutorial: Writing a Focus Listener
Since:
1.1/**
 * The listener interface for receiving keyboard focus events on
 * a component.
 * The class that is interested in processing a focus event
 * either implements this interface (and all the methods it
 * contains) or extends the abstract {@code FocusAdapter} class
 * (overriding only the methods of interest).
 * The listener object created from that class is then registered with a
 * component using the component's {@code addFocusListener}
 * method. When the component gains or loses the keyboard focus,
 * the relevant method in the listener object
 * is invoked, and the {@code FocusEvent} is passed to it.
 *
 * @see FocusAdapter
 * @see FocusEvent
 * @see <a href="http://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html">Tutorial: Writing a Focus Listener</a>
 *
 * @author Carl Quinn
 * @since 1.1
 */
public interface FocusListener extends EventListener {

    
Invoked when a component gains the keyboard focus.
Params:
e – the event to be processed/**
     * Invoked when a component gains the keyboard focus.
     * @param e the event to be processed
     */
    public void focusGained(FocusEvent e);

    
Invoked when a component loses the keyboard focus.
Params:
e – the event to be processed/**
     * Invoked when a component loses the keyboard focus.
     * @param e the event to be processed
     */
    public void focusLost(FocusEvent e);
}