Message.java revision a334e7c72408c4e2805f2427a35d841a60adefc4
1/* 2 * Copyright (C) 2006 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package android.os; 18 19import android.os.Bundle; 20import android.os.Parcel; 21import android.os.Parcelable; 22import android.util.TimeUtils; 23 24/** 25 * 26 * Defines a message containing a description and arbitrary data object that can be 27 * sent to a {@link Handler}. This object contains two extra int fields and an 28 * extra object field that allow you to not do allocations in many cases. 29 * 30 * <p class="note">While the constructor of Message is public, the best way to get 31 * one of these is to call {@link #obtain Message.obtain()} or one of the 32 * {@link Handler#obtainMessage Handler.obtainMessage()} methods, which will pull 33 * them from a pool of recycled objects.</p> 34 */ 35public final class Message implements Parcelable { 36 /** 37 * User-defined message code so that the recipient can identify 38 * what this message is about. Each {@link Handler} has its own name-space 39 * for message codes, so you do not need to worry about yours conflicting 40 * with other handlers. 41 */ 42 public int what; 43 44 /** 45 * arg1 and arg2 are lower-cost alternatives to using 46 * {@link #setData(Bundle) setData()} if you only need to store a 47 * few integer values. 48 */ 49 public int arg1; 50 51 /** 52 * arg1 and arg2 are lower-cost alternatives to using 53 * {@link #setData(Bundle) setData()} if you only need to store a 54 * few integer values. 55 */ 56 public int arg2; 57 58 /** 59 * An arbitrary object to send to the recipient. When using 60 * {@link Messenger} to send the message across processes this can only 61 * be non-null if it contains a Parcelable of a framework class (not one 62 * implemented by the application). For other data transfer use 63 * {@link #setData}. 64 * 65 * <p>Note that Parcelable objects here are not supported prior to 66 * the {@link android.os.Build.VERSION_CODES#FROYO} release. 67 */ 68 public Object obj; 69 70 /** 71 * Optional Messenger where replies to this message can be sent. The 72 * semantics of exactly how this is used are up to the sender and 73 * receiver. 74 */ 75 public Messenger replyTo; 76 77 /** If set message is in use */ 78 /*package*/ static final int FLAG_IN_USE = 1; 79 80 /** Flags reserved for future use (All are reserved for now) */ 81 /*package*/ static final int FLAGS_RESERVED = ~FLAG_IN_USE; 82 83 /** Flags to clear in the copyFrom method */ 84 /*package*/ static final int FLAGS_TO_CLEAR_ON_COPY_FROM = FLAGS_RESERVED | FLAG_IN_USE; 85 86 /*package*/ int flags; 87 88 /*package*/ long when; 89 90 /*package*/ Bundle data; 91 92 /*package*/ Handler target; 93 94 /*package*/ Runnable callback; 95 96 // sometimes we store linked lists of these things 97 /*package*/ Message next; 98 99 private static Object mPoolSync = new Object(); 100 private static Message mPool; 101 private static int mPoolSize = 0; 102 103 private static final int MAX_POOL_SIZE = 10; 104 105 /** 106 * Return a new Message instance from the global pool. Allows us to 107 * avoid allocating new objects in many cases. 108 */ 109 public static Message obtain() { 110 synchronized (mPoolSync) { 111 if (mPool != null) { 112 Message m = mPool; 113 mPool = m.next; 114 m.next = null; 115 return m; 116 } 117 } 118 return new Message(); 119 } 120 121 /** 122 * Same as {@link #obtain()}, but copies the values of an existing 123 * message (including its target) into the new one. 124 * @param orig Original message to copy. 125 * @return A Message object from the global pool. 126 */ 127 public static Message obtain(Message orig) { 128 Message m = obtain(); 129 m.what = orig.what; 130 m.arg1 = orig.arg1; 131 m.arg2 = orig.arg2; 132 m.obj = orig.obj; 133 m.replyTo = orig.replyTo; 134 if (orig.data != null) { 135 m.data = new Bundle(orig.data); 136 } 137 m.target = orig.target; 138 m.callback = orig.callback; 139 140 return m; 141 } 142 143 /** 144 * Same as {@link #obtain()}, but sets the value for the <em>target</em> member on the Message returned. 145 * @param h Handler to assign to the returned Message object's <em>target</em> member. 146 * @return A Message object from the global pool. 147 */ 148 public static Message obtain(Handler h) { 149 Message m = obtain(); 150 m.target = h; 151 152 return m; 153 } 154 155 /** 156 * Same as {@link #obtain(Handler)}, but assigns a callback Runnable on 157 * the Message that is returned. 158 * @param h Handler to assign to the returned Message object's <em>target</em> member. 159 * @param callback Runnable that will execute when the message is handled. 160 * @return A Message object from the global pool. 161 */ 162 public static Message obtain(Handler h, Runnable callback) { 163 Message m = obtain(); 164 m.target = h; 165 m.callback = callback; 166 167 return m; 168 } 169 170 /** 171 * Same as {@link #obtain()}, but sets the values for both <em>target</em> and 172 * <em>what</em> members on the Message. 173 * @param h Value to assign to the <em>target</em> member. 174 * @param what Value to assign to the <em>what</em> member. 175 * @return A Message object from the global pool. 176 */ 177 public static Message obtain(Handler h, int what) { 178 Message m = obtain(); 179 m.target = h; 180 m.what = what; 181 182 return m; 183 } 184 185 /** 186 * Same as {@link #obtain()}, but sets the values of the <em>target</em>, <em>what</em>, and <em>obj</em> 187 * members. 188 * @param h The <em>target</em> value to set. 189 * @param what The <em>what</em> value to set. 190 * @param obj The <em>object</em> method to set. 191 * @return A Message object from the global pool. 192 */ 193 public static Message obtain(Handler h, int what, Object obj) { 194 Message m = obtain(); 195 m.target = h; 196 m.what = what; 197 m.obj = obj; 198 199 return m; 200 } 201 202 /** 203 * Same as {@link #obtain()}, but sets the values of the <em>target</em>, <em>what</em>, 204 * <em>arg1</em>, and <em>arg2</em> members. 205 * 206 * @param h The <em>target</em> value to set. 207 * @param what The <em>what</em> value to set. 208 * @param arg1 The <em>arg1</em> value to set. 209 * @param arg2 The <em>arg2</em> value to set. 210 * @return A Message object from the global pool. 211 */ 212 public static Message obtain(Handler h, int what, int arg1, int arg2) { 213 Message m = obtain(); 214 m.target = h; 215 m.what = what; 216 m.arg1 = arg1; 217 m.arg2 = arg2; 218 219 return m; 220 } 221 222 /** 223 * Same as {@link #obtain()}, but sets the values of the <em>target</em>, <em>what</em>, 224 * <em>arg1</em>, <em>arg2</em>, and <em>obj</em> members. 225 * 226 * @param h The <em>target</em> value to set. 227 * @param what The <em>what</em> value to set. 228 * @param arg1 The <em>arg1</em> value to set. 229 * @param arg2 The <em>arg2</em> value to set. 230 * @param obj The <em>obj</em> value to set. 231 * @return A Message object from the global pool. 232 */ 233 public static Message obtain(Handler h, int what, 234 int arg1, int arg2, Object obj) { 235 Message m = obtain(); 236 m.target = h; 237 m.what = what; 238 m.arg1 = arg1; 239 m.arg2 = arg2; 240 m.obj = obj; 241 242 return m; 243 } 244 245 /** 246 * Return a Message instance to the global pool. You MUST NOT touch 247 * the Message after calling this function -- it has effectively been 248 * freed. 249 */ 250 public void recycle() { 251 synchronized (mPoolSync) { 252 if (mPoolSize < MAX_POOL_SIZE) { 253 clearForRecycle(); 254 255 next = mPool; 256 mPool = this; 257 } 258 } 259 } 260 261 /** 262 * Make this message like o. Performs a shallow copy of the data field. 263 * Does not copy the linked list fields, nor the timestamp or 264 * target/callback of the original message. 265 */ 266 public void copyFrom(Message o) { 267 this.flags = o.flags & ~FLAGS_TO_CLEAR_ON_COPY_FROM; 268 this.what = o.what; 269 this.arg1 = o.arg1; 270 this.arg2 = o.arg2; 271 this.obj = o.obj; 272 this.replyTo = o.replyTo; 273 274 if (o.data != null) { 275 this.data = (Bundle) o.data.clone(); 276 } else { 277 this.data = null; 278 } 279 } 280 281 /** 282 * Return the targeted delivery time of this message, in milliseconds. 283 */ 284 public long getWhen() { 285 return when; 286 } 287 288 public void setTarget(Handler target) { 289 this.target = target; 290 } 291 292 /** 293 * Retrieve the a {@link android.os.Handler Handler} implementation that 294 * will receive this message. The object must implement 295 * {@link android.os.Handler#handleMessage(android.os.Message) 296 * Handler.handleMessage()}. Each Handler has its own name-space for 297 * message codes, so you do not need to 298 * worry about yours conflicting with other handlers. 299 */ 300 public Handler getTarget() { 301 return target; 302 } 303 304 /** 305 * Retrieve callback object that will execute when this message is handled. 306 * This object must implement Runnable. This is called by 307 * the <em>target</em> {@link Handler} that is receiving this Message to 308 * dispatch it. If 309 * not set, the message will be dispatched to the receiving Handler's 310 * {@link Handler#handleMessage(Message Handler.handleMessage())}. 311 */ 312 public Runnable getCallback() { 313 return callback; 314 } 315 316 /** 317 * Obtains a Bundle of arbitrary data associated with this 318 * event, lazily creating it if necessary. Set this value by calling 319 * {@link #setData(Bundle)}. Note that when transferring data across 320 * processes via {@link Messenger}, you will need to set your ClassLoader 321 * on the Bundle via {@link Bundle#setClassLoader(ClassLoader) 322 * Bundle.setClassLoader()} so that it can instantiate your objects when 323 * you retrieve them. 324 * @see #peekData() 325 * @see #setData(Bundle) 326 */ 327 public Bundle getData() { 328 if (data == null) { 329 data = new Bundle(); 330 } 331 332 return data; 333 } 334 335 /** 336 * Like getData(), but does not lazily create the Bundle. A null 337 * is returned if the Bundle does not already exist. See 338 * {@link #getData} for further information on this. 339 * @see #getData() 340 * @see #setData(Bundle) 341 */ 342 public Bundle peekData() { 343 return data; 344 } 345 346 /** 347 * Sets a Bundle of arbitrary data values. Use arg1 and arg1 members 348 * as a lower cost way to send a few simple integer values, if you can. 349 * @see #getData() 350 * @see #peekData() 351 */ 352 public void setData(Bundle data) { 353 this.data = data; 354 } 355 356 /** 357 * Sends this Message to the Handler specified by {@link #getTarget}. 358 * Throws a null pointer exception if this field has not been set. 359 */ 360 public void sendToTarget() { 361 target.sendMessage(this); 362 } 363 364 /*package*/ void clearForRecycle() { 365 flags = 0; 366 what = 0; 367 arg1 = 0; 368 arg2 = 0; 369 obj = null; 370 replyTo = null; 371 when = 0; 372 target = null; 373 callback = null; 374 data = null; 375 } 376 377 /*package*/ boolean isInUse() { 378 return ((flags & FLAG_IN_USE) == FLAG_IN_USE); 379 } 380 381 /*package*/ void markInUse() { 382 flags |= FLAG_IN_USE; 383 } 384 385 /** Constructor (but the preferred way to get a Message is to call {@link #obtain() Message.obtain()}). 386 */ 387 public Message() { 388 } 389 390 public String toString() { 391 return toString(SystemClock.uptimeMillis()); 392 } 393 394 String toString(long now) { 395 StringBuilder b = new StringBuilder(); 396 397 b.append("{ what="); 398 b.append(what); 399 400 b.append(" when="); 401 TimeUtils.formatDuration(when-now, b); 402 403 if (arg1 != 0) { 404 b.append(" arg1="); 405 b.append(arg1); 406 } 407 408 if (arg2 != 0) { 409 b.append(" arg2="); 410 b.append(arg2); 411 } 412 413 if (obj != null) { 414 b.append(" obj="); 415 b.append(obj); 416 } 417 418 b.append(" }"); 419 420 return b.toString(); 421 } 422 423 public static final Parcelable.Creator<Message> CREATOR 424 = new Parcelable.Creator<Message>() { 425 public Message createFromParcel(Parcel source) { 426 Message msg = Message.obtain(); 427 msg.readFromParcel(source); 428 return msg; 429 } 430 431 public Message[] newArray(int size) { 432 return new Message[size]; 433 } 434 }; 435 436 public int describeContents() { 437 return 0; 438 } 439 440 public void writeToParcel(Parcel dest, int flags) { 441 if (callback != null) { 442 throw new RuntimeException( 443 "Can't marshal callbacks across processes."); 444 } 445 dest.writeInt(what); 446 dest.writeInt(arg1); 447 dest.writeInt(arg2); 448 if (obj != null) { 449 try { 450 Parcelable p = (Parcelable)obj; 451 dest.writeInt(1); 452 dest.writeParcelable(p, flags); 453 } catch (ClassCastException e) { 454 throw new RuntimeException( 455 "Can't marshal non-Parcelable objects across processes."); 456 } 457 } else { 458 dest.writeInt(0); 459 } 460 dest.writeLong(when); 461 dest.writeBundle(data); 462 Messenger.writeMessengerOrNullToParcel(replyTo, dest); 463 } 464 465 private final void readFromParcel(Parcel source) { 466 what = source.readInt(); 467 arg1 = source.readInt(); 468 arg2 = source.readInt(); 469 if (source.readInt() != 0) { 470 obj = source.readParcelable(getClass().getClassLoader()); 471 } 472 when = source.readLong(); 473 data = source.readBundle(); 474 replyTo = Messenger.readMessengerOrNullFromParcel(source); 475 } 476} 477