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250 lines
8.8 KiB
250 lines
8.8 KiB
/*
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* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package java.awt.event;
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import java.awt.Component;
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import sun.awt.AppContext;
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import sun.awt.SunToolkit;
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/**
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* A low-level event which indicates that a Component has gained or lost the
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* input focus. This low-level event is generated by a Component (such as a
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* TextField). The event is passed to every <code>FocusListener</code> or
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* <code>FocusAdapter</code> object which registered to receive such events
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* using the Component's <code>addFocusListener</code> method. (<code>
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* FocusAdapter</code> objects implement the <code>FocusListener</code>
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* interface.) Each such listener object gets this <code>FocusEvent</code> when
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* the event occurs.
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* <p>
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* There are two levels of focus events: permanent and temporary. Permanent
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* focus change events occur when focus is directly moved from one Component to
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* another, such as through a call to requestFocus() or as the user uses the
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* TAB key to traverse Components. Temporary focus change events occur when
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* focus is temporarily lost for a Component as the indirect result of another
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* operation, such as Window deactivation or a Scrollbar drag. In this case,
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* the original focus state will automatically be restored once that operation
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* is finished, or, for the case of Window deactivation, when the Window is
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* reactivated. Both permanent and temporary focus events are delivered using
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* the FOCUS_GAINED and FOCUS_LOST event ids; the level may be distinguished in
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* the event using the isTemporary() method.
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* <p>
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* An unspecified behavior will be caused if the {@code id} parameter
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* of any particular {@code FocusEvent} instance is not
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* in the range from {@code FOCUS_FIRST} to {@code FOCUS_LAST}.
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*
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* @see FocusAdapter
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* @see FocusListener
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* @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html">Tutorial: Writing a Focus Listener</a>
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*
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* @author Carl Quinn
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* @author Amy Fowler
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* @since 1.1
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*/
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public class FocusEvent extends ComponentEvent {
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/**
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* The first number in the range of ids used for focus events.
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*/
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public static final int FOCUS_FIRST = 1004;
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/**
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* The last number in the range of ids used for focus events.
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*/
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public static final int FOCUS_LAST = 1005;
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/**
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* This event indicates that the Component is now the focus owner.
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*/
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public static final int FOCUS_GAINED = FOCUS_FIRST; //Event.GOT_FOCUS
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/**
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* This event indicates that the Component is no longer the focus owner.
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*/
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public static final int FOCUS_LOST = 1 + FOCUS_FIRST; //Event.LOST_FOCUS
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/**
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* A focus event can have two different levels, permanent and temporary.
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* It will be set to true if some operation takes away the focus
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* temporarily and intends on getting it back once the event is completed.
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* Otherwise it will be set to false.
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*
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* @serial
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* @see #isTemporary
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*/
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boolean temporary;
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/**
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* The other Component involved in this focus change. For a FOCUS_GAINED
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* event, this is the Component that lost focus. For a FOCUS_LOST event,
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* this is the Component that gained focus. If this focus change occurs
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* with a native application, a Java application in a different VM, or with
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* no other Component, then the opposite Component is null.
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*
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* @see #getOppositeComponent
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* @since 1.4
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*/
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transient Component opposite;
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/*
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* JDK 1.1 serialVersionUID
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*/
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private static final long serialVersionUID = 523753786457416396L;
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/**
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* Constructs a <code>FocusEvent</code> object with the
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* specified temporary state and opposite <code>Component</code>.
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* The opposite <code>Component</code> is the other
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* <code>Component</code> involved in this focus change.
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* For a <code>FOCUS_GAINED</code> event, this is the
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* <code>Component</code> that lost focus. For a
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* <code>FOCUS_LOST</code> event, this is the <code>Component</code>
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* that gained focus. If this focus change occurs with a native
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* application, with a Java application in a different VM,
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* or with no other <code>Component</code>, then the opposite
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* <code>Component</code> is <code>null</code>.
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* <p> This method throws an
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* <code>IllegalArgumentException</code> if <code>source</code>
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* is <code>null</code>.
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*
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* @param source The <code>Component</code> that originated the event
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* @param id An integer indicating the type of event.
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* For information on allowable values, see
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* the class description for {@link FocusEvent}
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* @param temporary Equals <code>true</code> if the focus change is temporary;
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* <code>false</code> otherwise
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* @param opposite The other Component involved in the focus change,
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* or <code>null</code>
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* @throws IllegalArgumentException if <code>source</code> equals {@code null}
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* @see #getSource()
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* @see #getID()
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* @see #isTemporary()
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* @see #getOppositeComponent()
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* @since 1.4
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*/
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public FocusEvent(Component source, int id, boolean temporary,
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Component opposite) {
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super(source, id);
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this.temporary = temporary;
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this.opposite = opposite;
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}
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/**
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* Constructs a <code>FocusEvent</code> object and identifies
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* whether or not the change is temporary.
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* <p> This method throws an
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* <code>IllegalArgumentException</code> if <code>source</code>
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* is <code>null</code>.
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*
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* @param source The <code>Component</code> that originated the event
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* @param id An integer indicating the type of event.
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* For information on allowable values, see
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* the class description for {@link FocusEvent}
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* @param temporary Equals <code>true</code> if the focus change is temporary;
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* <code>false</code> otherwise
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* @throws IllegalArgumentException if <code>source</code> equals {@code null}
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* @see #getSource()
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* @see #getID()
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* @see #isTemporary()
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*/
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public FocusEvent(Component source, int id, boolean temporary) {
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this(source, id, temporary, null);
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}
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/**
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* Constructs a <code>FocusEvent</code> object and identifies it
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* as a permanent change in focus.
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* <p> This method throws an
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* <code>IllegalArgumentException</code> if <code>source</code>
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* is <code>null</code>.
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*
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* @param source The <code>Component</code> that originated the event
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* @param id An integer indicating the type of event.
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* For information on allowable values, see
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* the class description for {@link FocusEvent}
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* @throws IllegalArgumentException if <code>source</code> equals {@code null}
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* @see #getSource()
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* @see #getID()
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*/
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public FocusEvent(Component source, int id) {
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this(source, id, false);
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}
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/**
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* Identifies the focus change event as temporary or permanent.
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*
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* @return <code>true</code> if the focus change is temporary;
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* <code>false</code> otherwise
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*/
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public boolean isTemporary() {
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return temporary;
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}
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/**
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* Returns the other Component involved in this focus change. For a
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* FOCUS_GAINED event, this is the Component that lost focus. For a
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* FOCUS_LOST event, this is the Component that gained focus. If this
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* focus change occurs with a native application, with a Java application
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* in a different VM or context, or with no other Component, then null is
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* returned.
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*
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* @return the other Component involved in the focus change, or null
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* @since 1.4
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*/
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public Component getOppositeComponent() {
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if (opposite == null) {
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return null;
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}
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return (SunToolkit.targetToAppContext(opposite) ==
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AppContext.getAppContext())
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? opposite
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: null;
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}
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/**
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* Returns a parameter string identifying this event.
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* This method is useful for event-logging and for debugging.
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*
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* @return a string identifying the event and its attributes
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*/
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public String paramString() {
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String typeStr;
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switch(id) {
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case FOCUS_GAINED:
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typeStr = "FOCUS_GAINED";
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break;
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case FOCUS_LOST:
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typeStr = "FOCUS_LOST";
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break;
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default:
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typeStr = "unknown type";
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}
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return typeStr + (temporary ? ",temporary" : ",permanent") +
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",opposite=" + getOppositeComponent();
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}
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}
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