/*
* @(#)FocusEvent.java 1.30 03/12/19
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.awt.event;
import java.awt.Component;
import java.awt.Event;
import sun.awt.AppContext;
import sun.awt.SunToolkit;
/**
* A low-level event which indicates that a Component has gained or lost the
* input focus. This low-level event is generated by a Component (such as a
* TextField). The event is passed to every <code>FocusListener</code> or
* <code>FocusAdapter</code> object which registered to receive such events
* using the Component's <code>addFocusListener</code> method. (<code>
* FocusAdapter</code> objects implement the <code>FocusListener</code>
* interface.) Each such listener object gets this <code>FocusEvent</code> when
* the event occurs.
* <p>
* There are two levels of focus events: permanent and temporary. Permanent
* focus change events occur when focus is directly moved from one Component to
* another, such as through a call to requestFocus() or as the user uses the
* TAB key to traverse Components. Temporary focus change events occur when
* focus is temporarily lost for a Component as the indirect result of another
* operation, such as Window deactivation or a Scrollbar drag. In this case,
* the original focus state will automatically be restored once that operation
* is finished, or, for the case of Window deactivation, when the Window is
* reactivated. Both permanent and temporary focus events are delivered using
* the FOCUS_GAINED and FOCUS_LOST event ids; the level may be distinguished in
* the event using the isTemporary() method.
*
* @see FocusAdapter
* @see FocusListener
* @see <a href="http://java.sun.com/docs/books/tutorial/post1.0/ui/focuslistener.html">Tutorial: Writing a Focus Listener</a>
* @see <a href="http://www.awl.com/cp/javaseries/jcl1_2.html">Reference: The Java Class Libraries (update file)</a>
*
* @author Carl Quinn
* @author Amy Fowler
* @version 1.30 12/19/03
* @since 1.1
*/
public class FocusEvent extends ComponentEvent {
/**
* The first number in the range of ids used for focus events.
*/
public static final int FOCUS_FIRST = 1004;
/**
* The last number in the range of ids used for focus events.
*/
public static final int FOCUS_LAST = 1005;
/**
* This event indicates that the Component is now the focus owner.
*/
public static final int FOCUS_GAINED = FOCUS_FIRST; //Event.GOT_FOCUS
/**
* This event indicates that the Component is no longer the focus owner.
*/
public static final int FOCUS_LOST = 1 + FOCUS_FIRST; //Event.LOST_FOCUS
/**
* A focus event can have two different levels, permanent and temporary.
* It will be set to true if some operation takes away the focus
* temporarily and intends on getting it back once the event is completed.
* Otherwise it will be set to false.
*
* @serial
* @see #isTemporary
*/
boolean temporary;
/**
* The other Component involved in this focus change. For a FOCUS_GAINED
* event, this is the Component that lost focus. For a FOCUS_LOST event,
* this is the Component that gained focus. If this focus change occurs
* with a native application, a Java application in a different VM, or with
* no other Component, then the opposite Component is null.
*
* @see #getOppositeComponent
* @since 1.4
*/
transient Component opposite;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = 523753786457416396L;
/**
* Constructs a <code>FocusEvent</code> object with the
* specified temporary state and opposite <code>Component</code>.
* The opposite <code>Component</code> is the other
* <code>Component</code> involved in this focus change.
* For a <code>FOCUS_GAINED</code> event, this is the
* <code>Component</code> that lost focus. For a
* <code>FOCUS_LOST</code> event, this is the <code>Component</code>
* that gained focus. If this focus change occurs with a native
* application, with a Java application in a different VM,
* or with no other <code>Component</code>, then the opposite
* <code>Component</code> is <code>null</code>.
* <p>Note that passing in an invalid <code>id</code> results in
* unspecified behavior. This method throws an
* <code>IllegalArgumentException</code> if <code>source</code>
* is <code>null</code>.
*
* @param source the <code>Component</code> that originated the event
* @param id <code>FOCUS_GAINED</code> or <code>FOCUS_LOST</code>
* @param temporary <code>true</code> if the focus change is temporary;
* <code>false</code> otherwise
* @param opposite the other Component involved in the focus change,
* or <code>null</code>
* @throws IllegalArgumentException if <code>source</code> is null
*/
public FocusEvent(Component source, int id, boolean temporary,
Component opposite) {
super(source, id);
this.temporary = temporary;
this.opposite = opposite;
}
/**
* Constructs a <code>FocusEvent</code> object and identifies
* whether or not the change is temporary.
* <p>Note that passing in an invalid <code>id</code> results in
* unspecified behavior. This method throws an
* <code>IllegalArgumentException</code> if <code>source</code>
* is <code>null</code>.
*
* @param source the <code>Component</code> that originated the event
* @param id an integer indicating the type of event
* @param temporary <code>true</code> if the focus change is temporary;
* <code>false</code> otherwise
* @throws IllegalArgumentException if <code>source</code> is null
*/
public FocusEvent(Component source, int id, boolean temporary) {
this(source, id, temporary, null);
}
/**
* Constructs a <code>FocusEvent</code> object and identifies it
* as a permanent change in focus.
* <p>Note that passing in an invalid <code>id</code> results in
* unspecified behavior. This method throws an
* <code>IllegalArgumentException</code> if <code>source</code>
* is <code>null</code>.
*
* @param source the <code>Component</code> that originated the event
* @param id an integer indicating the type of event
* @throws IllegalArgumentException if <code>source</code> is null
*/
public FocusEvent(Component source, int id) {
this(source, id, false);
}
/**
* Identifies the focus change event as temporary or permanent.
*
* @return <code>true</code> if the focus change is temporary;
* <code>false</code> otherwise
*/
public boolean isTemporary() {
return temporary;
}
/**
* Returns the other Component involved in this focus change. For a
* FOCUS_GAINED event, this is the Component that lost focus. For a
* FOCUS_LOST event, this is the Component that gained focus. If this
* focus change occurs with a native application, with a Java application
* in a different VM or context, or with no other Component, then null is
* returned.
*
* @return the other Component involved in the focus change, or null
* @since 1.4
*/
public Component getOppositeComponent() {
if (opposite == null) {
return null;
}
return (SunToolkit.targetToAppContext(opposite) ==
AppContext.getAppContext())
? opposite
: null;
}
/**
* Returns a parameter string identifying this event.
* This method is useful for event-logging and for debugging.
*
* @return a string identifying the event and its attributes
*/
public String paramString() {
String typeStr;
switch(id) {
case FOCUS_GAINED:
typeStr = "FOCUS_GAINED";
break;
case FOCUS_LOST:
typeStr = "FOCUS_LOST";
break;
default:
typeStr = "unknown type";
}
return typeStr + (temporary ? ",temporary" : ",permanent") +
",opposite=" + getOppositeComponent();
}
}
|
