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 sun.awt.AppContext;
29 import sun.awt.SunToolkit;
30
31 import java.awt.*;
32
33 /**
34 * A low-level event which indicates that a Component has gained or lost the
35 * input focus. This low-level event is generated by a Component (such as a
36 * TextField). The event is passed to every {@code FocusListener} or
37 * {@code FocusAdapter} object which registered to receive such events
38 * using the Component's {@code addFocusListener} method. ({@code
39 * FocusAdapter} objects implement the {@code FocusListener}
40 * interface.) Each such listener object gets this {@code FocusEvent} when
41 * the event occurs.
42 * <p>
43 * There are two levels of focus events: permanent and temporary. Permanent
44 * focus change events occur when focus is directly moved from one Component to
45 * another, such as through a call to requestFocus() or as the user uses the
46 * TAB key to traverse Components. Temporary focus change events occur when
47 * focus is temporarily lost for a Component as the indirect result of another
48 * operation, such as Window deactivation or a Scrollbar drag. In this case,
49 * the original focus state will automatically be restored once that operation
50 * is finished, or, for the case of Window deactivation, when the Window is
51 * reactivated. Both permanent and temporary focus events are delivered using
52 * the FOCUS_GAINED and FOCUS_LOST event ids; the level may be distinguished in
53 * the event using the isTemporary() method.
54 * <p>
55 * Every {@code FocusEvent} records its cause - the reason why this event was generated.
56 * The cause is assigned during the focus event creation and may be retrieved by
57 * calling {@link #getCause}.
58 * <p>
59 * An unspecified behavior will be caused if the {@code id} parameter
60 * of any particular {@code FocusEvent} instance is not
61 * in the range from {@code FOCUS_FIRST} to {@code FOCUS_LAST}.
62 *
63 * @see FocusAdapter
64 * @see FocusListener
65 * @see <a href="http://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html">Tutorial: Writing a Focus Listener</a>
66 *
67 * @author Carl Quinn
68 * @author Amy Fowler
69 * @since 1.1
70 */
71 public class FocusEvent extends ComponentEvent {
72
73 /**
74 * This enum represents the cause of a {@code FocusEvent}- the reason why it occurred.
75 * Possible reasons include mouse events, keyboard focus traversal, window activation.
76 * If no cause is provided then the reason is {@code UNKNOWN}.
77 *
78 * @since 1.9
79 */
80 public enum Cause {
81 /**
82 * The default value.
83 */
84 UNKNOWN,
85 /**
86 * An activating mouse event.
87 */
88 MOUSE_EVENT,
89 /**
90 * A focus traversal action with unspecified direction.
91 */
92 TRAVERSAL,
93 /**
94 * An up-cycle focus traversal action.
95 */
96 TRAVERSAL_UP,
97 /**
98 * A down-cycle focus traversal action.
99 */
100 TRAVERSAL_DOWN,
101 /**
102 * A forward focus traversal action.
103 */
104 TRAVERSAL_FORWARD,
105 /**
106 * A backward focus traversal action.
107 */
108 TRAVERSAL_BACKWARD,
109 /**
110 * Restoring focus after a focus request has been rejected.
111 */
112 ROLLBACK,
113 /**
114 * A system action causing an unexpected focus change.
115 */
116 UNEXPECTED,
117 /**
118 * An activation of a toplevel window.
119 */
120 ACTIVATION,
121 /**
122 * Clearing global focus owner.
123 */
124 CLEAR_GLOBAL_FOCUS_OWNER
125 }
126
127 /**
128 * The first number in the range of ids used for focus events.
129 */
130 public static final int FOCUS_FIRST = 1004;
131
132 /**
133 * The last number in the range of ids used for focus events.
134 */
135 public static final int FOCUS_LAST = 1005;
136
137 /**
138 * This event indicates that the Component is now the focus owner.
139 */
140 public static final int FOCUS_GAINED = FOCUS_FIRST; //Event.GOT_FOCUS
141
142 /**
143 * This event indicates that the Component is no longer the focus owner.
144 */
145 public static final int FOCUS_LOST = 1 + FOCUS_FIRST; //Event.LOST_FOCUS
146
147 private final Cause cause;
148
149 /**
150 * A focus event can have two different levels, permanent and temporary.
151 * It will be set to true if some operation takes away the focus
152 * temporarily and intends on getting it back once the event is completed.
153 * Otherwise it will be set to false.
154 *
155 * @serial
156 * @see #isTemporary
157 */
158 boolean temporary;
159
160 /**
161 * The other Component involved in this focus change. For a FOCUS_GAINED
162 * event, this is the Component that lost focus. For a FOCUS_LOST event,
163 * this is the Component that gained focus. If this focus change occurs
164 * with a native application, a Java application in a different VM, or with
165 * no other Component, then the opposite Component is null.
166 *
167 * @see #getOppositeComponent
168 * @since 1.4
169 */
170 transient Component opposite;
171
172 /*
173 * JDK 1.1 serialVersionUID
174 */
175 private static final long serialVersionUID = 523753786457416396L;
176
177 /**
178 * Constructs a {@code FocusEvent} object with the
179 * specified temporary state and opposite {@code Component} and the
180 * {@code Cause.UNKNOWN} cause.
181 * The opposite {@code Component} is the other
182 * {@code Component} involved in this focus change.
183 * For a {@code FOCUS_GAINED} event, this is the
184 * {@code Component} that lost focus. For a
185 * {@code FOCUS_LOST} event, this is the {@code Component}
186 * that gained focus. If this focus change occurs with a native
187 * application, with a Java application in a different VM,
188 * or with no other {@code Component}, then the opposite
189 * {@code Component} is {@code null}.
190 * <p> This method throws an
191 * {@code IllegalArgumentException} if {@code source}
192 * is {@code null}.
193 *
194 * @param source The {@code Component} that originated the event
195 * @param id An integer indicating the type of event.
196 * For information on allowable values, see
197 * the class description for {@link FocusEvent}
198 * @param temporary Equals {@code true} if the focus change is temporary;
199 * {@code false} otherwise
200 * @param opposite The other Component involved in the focus change,
201 * or {@code null}
202 * @throws IllegalArgumentException if {@code source} equals {@code null}
203 * @see #getSource()
204 * @see #getID()
205 * @see #isTemporary()
206 * @see #getOppositeComponent()
207 * @see Cause#UNKNOWN
208 * @since 1.4
209 */
210 public FocusEvent(Component source, int id, boolean temporary,
211 Component opposite) {
212 this(source, id, temporary, opposite, Cause.UNKNOWN);
213 }
214
215 /**
216 * Constructs a {@code FocusEvent} object with the
217 * specified temporary state, opposite {@code Component} and the cause.
218 * The opposite {@code Component} is the other
219 * {@code Component} involved in this focus change.
220 * For a {@code FOCUS_GAINED} event, this is the
221 * {@code Component} that lost focus. For a
222 * {@code FOCUS_LOST} event, this is the {@code Component}
223 * that gained focus. If this focus change occurs with a native
224 * application, with a Java application in a different VM,
225 * or with no other {@code Component}, then the opposite
226 * {@code Component} is {@code null}.
227 * <p> This method throws an
228 * {@code IllegalArgumentException} if {@code source}
229 * is {@code null}.
230 *
231 * @param source The {@code Component} that originated the event
232 * @param id An integer indicating the type of event.
233 * For information on allowable values, see
234 * the class description for {@link FocusEvent}
235 * @param temporary Equals {@code true} if the focus change is temporary;
236 * {@code false} otherwise
237 * @param opposite The other Component involved in the focus change,
238 * or {@code null}
239 * @param cause The focus event cause.
240 * @throws IllegalArgumentException if {@code source} equals {@code null}
241 * or if {@code cause} equals {@code null}
242 * @see #getSource()
243 * @see #getID()
244 * @see #isTemporary()
245 * @see #getOppositeComponent()
246 * @see Cause
247 * @since 1.9
248 */
249 public FocusEvent(Component source, int id, boolean temporary,
250 Component opposite, Cause cause) {
251 super(source, id);
252 if (source == null)
253 throw new IllegalArgumentException("null cause");
254 this.temporary = temporary;
255 this.opposite = opposite;
256 this.cause = cause;
257 }
258
259 /**
260 * Constructs a {@code FocusEvent} object and identifies
261 * whether or not the change is temporary.
262 * <p> This method throws an
263 * {@code IllegalArgumentException} if {@code source}
264 * is {@code null}.
265 *
266 * @param source The {@code Component} that originated the event
267 * @param id An integer indicating the type of event.
268 * For information on allowable values, see
269 * the class description for {@link FocusEvent}
270 * @param temporary Equals {@code true} if the focus change is temporary;
271 * {@code false} otherwise
272 * @throws IllegalArgumentException if {@code source} equals {@code null}
273 * @see #getSource()
274 * @see #getID()
275 * @see #isTemporary()
276 */
277 public FocusEvent(Component source, int id, boolean temporary) {
278 this(source, id, temporary, null);
279 }
280
281 /**
282 * Constructs a {@code FocusEvent} object and identifies it
283 * as a permanent change in focus.
284 * <p> This method throws an
285 * {@code IllegalArgumentException} if {@code source}
286 * is {@code null}.
287 *
288 * @param source The {@code Component} that originated the event
289 * @param id An integer indicating the type of event.
290 * For information on allowable values, see
291 * the class description for {@link FocusEvent}
292 * @throws IllegalArgumentException if {@code source} equals {@code null}
293 * @see #getSource()
294 * @see #getID()
295 */
296 public FocusEvent(Component source, int id) {
297 this(source, id, false);
298 }
299
300 /**
301 * Identifies the focus change event as temporary or permanent.
302 *
303 * @return {@code true} if the focus change is temporary;
304 * {@code false} otherwise
305 */
306 public boolean isTemporary() {
307 return temporary;
308 }
309
310 /**
311 * Returns the other Component involved in this focus change. For a
312 * FOCUS_GAINED event, this is the Component that lost focus. For a
313 * FOCUS_LOST event, this is the Component that gained focus. If this
314 * focus change occurs with a native application, with a Java application
315 * in a different VM or context, or with no other Component, then null is
316 * returned.
317 *
318 * @return the other Component involved in the focus change, or null
319 * @since 1.4
320 */
321 public Component getOppositeComponent() {
322 if (opposite == null) {
323 return null;
324 }
325
326 return (SunToolkit.targetToAppContext(opposite) ==
327 AppContext.getAppContext())
328 ? opposite
329 : null;
330 }
331
332 /**
333 * Returns a parameter string identifying this event.
334 * This method is useful for event-logging and for debugging.
335 *
336 * @return a string identifying the event and its attributes
337 */
338 public String paramString() {
339 String typeStr;
340 switch(id) {
341 case FOCUS_GAINED:
342 typeStr = "FOCUS_GAINED";
343 break;
344 case FOCUS_LOST:
345 typeStr = "FOCUS_LOST";
346 break;
347 default:
348 typeStr = "unknown type";
349 }
350 return typeStr + (temporary ? ",temporary" : ",permanent") +
351 ",opposite=" + getOppositeComponent() + ",cause=" + getCause();
352 }
353
354 /**
355 * Returns the event cause.
356 *
357 * @return one of {@link Cause} values
358 * @since 1.9
359 */
360 public Cause getCause() {
361 return cause;
362 }
363 }