1 /*
2 * Copyright (c) 1996, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.awt.event;
27
28 import java.awt.Component;
29 import java.io.ObjectStreamException;
30
31 import sun.awt.AWTAccessor;
32 import sun.awt.AppContext;
33 import sun.awt.SunToolkit;
34
35 /**
36 * A low-level event which indicates that a Component has gained or lost the
37 * input focus. This low-level event is generated by a Component (such as a
38 * TextField). The event is passed to every {@code FocusListener} or
39 * {@code FocusAdapter} object which registered to receive such events
40 * using the Component's {@code addFocusListener} method.
41 * ({@code FocusAdapter} objects implement the {@code FocusListener}
42 * interface.) Each such listener object gets this {@code FocusEvent} when
43 * the event occurs.
44 * <p>
45 * There are two levels of focus events: permanent and temporary. Permanent
46 * focus change events occur when focus is directly moved from one Component to
47 * another, such as through a call to requestFocus() or as the user uses the
48 * TAB key to traverse Components. Temporary focus change events occur when
49 * focus is temporarily lost for a Component as the indirect result of another
50 * operation, such as Window deactivation or a Scrollbar drag. In this case,
51 * the original focus state will automatically be restored once that operation
52 * is finished, or, for the case of Window deactivation, when the Window is
53 * reactivated. Both permanent and temporary focus events are delivered using
54 * the FOCUS_GAINED and FOCUS_LOST event ids; the level may be distinguished in
55 * the event using the isTemporary() method.
56 * <p>
57 * Every {@code FocusEvent} records its cause - the reason why this event was
58 * generated. The cause is assigned during the focus event creation and may be
59 * retrieved by calling {@link #getCause}.
60 * <p>
61 * An unspecified behavior will be caused if the {@code id} parameter
62 * of any particular {@code FocusEvent} instance is not
63 * in the range from {@code FOCUS_FIRST} to {@code FOCUS_LAST}.
64 *
65 * @see FocusAdapter
66 * @see FocusListener
67 * @see <a href="http://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html">Tutorial: Writing a Focus Listener</a>
68 *
69 * @author Carl Quinn
70 * @author Amy Fowler
71 * @since 1.1
72 */
73 public class FocusEvent extends ComponentEvent {
74
75 /**
76 * This enum represents the cause of a {@code FocusEvent}- the reason why it
77 * occurred. Possible reasons include mouse events, keyboard focus
78 * traversal, window activation.
79 * If no cause is provided then the reason is {@code UNKNOWN}.
80 *
81 * @since 9
82 */
83 public enum Cause {
84 /**
85 * The default value.
86 */
87 UNKNOWN,
88 /**
89 * An activating mouse event.
90 */
91 MOUSE_EVENT,
92 /**
93 * A focus traversal action with unspecified direction.
94 */
95 TRAVERSAL,
96 /**
97 * An up-cycle focus traversal action.
98 */
99 TRAVERSAL_UP,
100 /**
101 * A down-cycle focus traversal action.
102 */
103 TRAVERSAL_DOWN,
104 /**
105 * A forward focus traversal action.
106 */
107 TRAVERSAL_FORWARD,
108 /**
109 * A backward focus traversal action.
110 */
111 TRAVERSAL_BACKWARD,
112 /**
113 * Restoring focus after a focus request has been rejected.
114 */
115 ROLLBACK,
116 /**
117 * A system action causing an unexpected focus change.
118 */
119 UNEXPECTED,
120 /**
121 * An activation of a toplevel window.
122 */
123 ACTIVATION,
124 /**
125 * Clearing global focus owner.
126 */
127 CLEAR_GLOBAL_FOCUS_OWNER
128 }
129
130 /**
131 * The first number in the range of ids used for focus events.
132 */
133 public static final int FOCUS_FIRST = 1004;
134
135 /**
136 * The last number in the range of ids used for focus events.
137 */
138 public static final int FOCUS_LAST = 1005;
139
140 /**
141 * This event indicates that the Component is now the focus owner.
142 */
143 public static final int FOCUS_GAINED = FOCUS_FIRST; //Event.GOT_FOCUS
144
145 /**
146 * This event indicates that the Component is no longer the focus owner.
147 */
148 public static final int FOCUS_LOST = 1 + FOCUS_FIRST; //Event.LOST_FOCUS
149
150 private final Cause cause;
151
152 /**
153 * A focus event can have two different levels, permanent and temporary.
154 * It will be set to true if some operation takes away the focus
155 * temporarily and intends on getting it back once the event is completed.
156 * Otherwise it will be set to false.
157 *
158 * @serial
159 * @see #isTemporary
160 */
161 boolean temporary;
162
163 /**
164 * The other Component involved in this focus change. For a FOCUS_GAINED
165 * event, this is the Component that lost focus. For a FOCUS_LOST event,
166 * this is the Component that gained focus. If this focus change occurs
167 * with a native application, a Java application in a different VM, or with
168 * no other Component, then the opposite Component is null.
169 *
170 * @see #getOppositeComponent
171 * @since 1.4
172 */
173 transient Component opposite;
174
175 /*
176 * JDK 1.1 serialVersionUID
177 */
178 private static final long serialVersionUID = 523753786457416396L;
179
180 /**
181 * Constructs a {@code FocusEvent} object with the
182 * specified temporary state, opposite {@code Component} and the
183 * {@code Cause.UNKNOWN} cause.
184 * The opposite {@code Component} is the other
185 * {@code Component} involved in this focus change.
186 * For a {@code FOCUS_GAINED} event, this is the
187 * {@code Component} that lost focus. For a
188 * {@code FOCUS_LOST} event, this is the {@code Component}
189 * that gained focus. If this focus change occurs with a native
190 * application, with a Java application in a different VM,
191 * or with no other {@code Component}, then the opposite
192 * {@code Component} is {@code null}.
193 * <p> This method throws an
194 * {@code IllegalArgumentException} if {@code source}
195 * is {@code null}.
196 *
197 * @param source The {@code Component} that originated the event
198 * @param id An integer indicating the type of event.
199 * For information on allowable values, see
200 * the class description for {@link FocusEvent}
201 * @param temporary Equals {@code true} if the focus change is temporary;
202 * {@code false} otherwise
203 * @param opposite The other Component involved in the focus change,
204 * or {@code null}
205 * @throws IllegalArgumentException if {@code source} equals {@code null}
206 * @see #getSource()
207 * @see #getID()
208 * @see #isTemporary()
209 * @see #getOppositeComponent()
210 * @see Cause#UNKNOWN
211 * @since 1.4
212 */
213 public FocusEvent(Component source, int id, boolean temporary,
214 Component opposite) {
215 this(source, id, temporary, opposite, Cause.UNKNOWN);
216 }
217
218 /**
219 * Constructs a {@code FocusEvent} object with the
220 * specified temporary state, opposite {@code Component} and the cause.
221 * The opposite {@code Component} is the other
222 * {@code Component} involved in this focus change.
223 * For a {@code FOCUS_GAINED} event, this is the
224 * {@code Component} that lost focus. For a
225 * {@code FOCUS_LOST} event, this is the {@code Component}
226 * that gained focus. If this focus change occurs with a native
227 * application, with a Java application in a different VM,
228 * or with no other {@code Component}, then the opposite
229 * {@code Component} is {@code null}.
230 * <p> This method throws an
231 * {@code IllegalArgumentException} if {@code source} or {@code cause}
232 * is {@code null}.
233 *
234 * @param source The {@code Component} that originated the event
235 * @param id An integer indicating the type of event.
236 * For information on allowable values, see
237 * the class description for {@link FocusEvent}
238 * @param temporary Equals {@code true} if the focus change is temporary;
239 * {@code false} otherwise
240 * @param opposite The other Component involved in the focus change,
241 * or {@code null}
242 * @param cause The focus event cause.
243 * @throws IllegalArgumentException if {@code source} equals {@code null}
244 * or if {@code cause} equals {@code null}
245 * @see #getSource()
246 * @see #getID()
247 * @see #isTemporary()
248 * @see #getOppositeComponent()
249 * @see Cause
250 * @since 9
251 */
252 public FocusEvent(Component source, int id, boolean temporary,
253 Component opposite, Cause cause) {
254 super(source, id);
255 if (cause == null) {
256 throw new IllegalArgumentException("null cause");
257 }
258 this.temporary = temporary;
259 this.opposite = opposite;
260 this.cause = cause;
261 }
262
263 /**
264 * Constructs a {@code FocusEvent} object and identifies
265 * whether or not the change is temporary.
266 * <p> This method throws an
267 * {@code IllegalArgumentException} if {@code source}
268 * is {@code null}.
269 *
270 * @param source The {@code Component} that originated the event
271 * @param id An integer indicating the type of event.
272 * For information on allowable values, see
273 * the class description for {@link FocusEvent}
274 * @param temporary Equals {@code true} if the focus change is temporary;
275 * {@code false} otherwise
276 * @throws IllegalArgumentException if {@code source} equals {@code null}
277 * @see #getSource()
278 * @see #getID()
279 * @see #isTemporary()
280 */
281 public FocusEvent(Component source, int id, boolean temporary) {
282 this(source, id, temporary, null);
283 }
284
285 /**
286 * Constructs a {@code FocusEvent} object and identifies it
287 * as a permanent change in focus.
288 * <p> This method throws an
289 * {@code IllegalArgumentException} if {@code source}
290 * is {@code null}.
291 *
292 * @param source The {@code Component} that originated the event
293 * @param id An integer indicating the type of event.
294 * For information on allowable values, see
295 * the class description for {@link FocusEvent}
296 * @throws IllegalArgumentException if {@code source} equals {@code null}
297 * @see #getSource()
298 * @see #getID()
299 */
300 public FocusEvent(Component source, int id) {
301 this(source, id, false);
302 }
303
304 /**
305 * Identifies the focus change event as temporary or permanent.
306 *
307 * @return {@code true} if the focus change is temporary;
308 * {@code false} otherwise
309 */
310 public boolean isTemporary() {
311 return temporary;
312 }
313
314 /**
315 * Returns the other Component involved in this focus change. For a
316 * FOCUS_GAINED event, this is the Component that lost focus. For a
317 * FOCUS_LOST event, this is the Component that gained focus. If this
318 * focus change occurs with a native application, with a Java application
319 * in a different VM or context, or with no other Component, then null is
320 * returned.
321 *
322 * @return the other Component involved in the focus change, or null
323 * @since 1.4
324 */
325 public Component getOppositeComponent() {
326 if (opposite == null) {
327 return null;
328 }
329
330 return (SunToolkit.targetToAppContext(opposite) ==
331 AppContext.getAppContext())
332 ? opposite
333 : null;
334 }
335
336 /**
337 * Returns a parameter string identifying this event.
338 * This method is useful for event-logging and for debugging.
339 *
340 * @return a string identifying the event and its attributes
341 */
342 public String paramString() {
343 String typeStr;
344 switch(id) {
345 case FOCUS_GAINED:
346 typeStr = "FOCUS_GAINED";
347 break;
348 case FOCUS_LOST:
349 typeStr = "FOCUS_LOST";
350 break;
351 default:
352 typeStr = "unknown type";
353 }
354 return typeStr + (temporary ? ",temporary" : ",permanent") +
355 ",opposite=" + getOppositeComponent() + ",cause=" + getCause();
356 }
357
358 /**
359 * Returns the event cause.
360 *
361 * @return one of {@link Cause} values
362 * @since 9
363 */
364 public final Cause getCause() {
365 return cause;
366 }
367
368 // Ensure that the deserialized object is compatible
369 @SuppressWarnings("serial")
370 Object readResolve() throws ObjectStreamException {
371 if (cause != null) {
372 return this;
373 }
374 FocusEvent focusEvent = new FocusEvent(new Component(){}, getID(),
375 isTemporary(), getOppositeComponent());
376 focusEvent.setSource(null);
377 focusEvent.consumed = consumed;
378
379 AWTAccessor.AWTEventAccessor accessor =
380 AWTAccessor.getAWTEventAccessor();
381 accessor.setBData(focusEvent, accessor.getBData(this));
382 return focusEvent;
383 }
384
385
386 }