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 17 package android.os; 18 19 import android.os.Bundle; 20 import android.os.Parcel; 21 import android.os.Parcelable; 22 import 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 */ 35 public 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 /*package*/ long when; 78 79 /*package*/ Bundle data; 80 81 /*package*/ Handler target; 82 83 /*package*/ Runnable callback; 84 85 // sometimes we store linked lists of these things 86 /*package*/ Message next; 87 88 private static Object mPoolSync = new Object(); 89 private static Message mPool; 90 private static int mPoolSize = 0; 91 92 private static final int MAX_POOL_SIZE = 10; 93 94 /** 95 * Return a new Message instance from the global pool. Allows us to 96 * avoid allocating new objects in many cases. 97 */ 98 public static Message obtain() { 99 synchronized (mPoolSync) { 100 if (mPool != null) { 101 Message m = mPool; 102 mPool = m.next; 103 m.next = null; 104 return m; 105 } 106 } 107 return new Message(); 108 } 109 110 /** 111 * Same as {@link #obtain()}, but copies the values of an existing 112 * message (including its target) into the new one. 113 * @param orig Original message to copy. 114 * @return A Message object from the global pool. 115 */ 116 public static Message obtain(Message orig) { 117 Message m = obtain(); 118 m.what = orig.what; 119 m.arg1 = orig.arg1; 120 m.arg2 = orig.arg2; 121 m.obj = orig.obj; 122 m.replyTo = orig.replyTo; 123 if (orig.data != null) { 124 m.data = new Bundle(orig.data); 125 } 126 m.target = orig.target; 127 m.callback = orig.callback; 128 129 return m; 130 } 131 132 /** 133 * Same as {@link #obtain()}, but sets the value for the <em>target</em> member on the Message returned. 134 * @param h Handler to assign to the returned Message object's <em>target</em> member. 135 * @return A Message object from the global pool. 136 */ 137 public static Message obtain(Handler h) { 138 Message m = obtain(); 139 m.target = h; 140 141 return m; 142 } 143 144 /** 145 * Same as {@link #obtain(Handler)}, but assigns a callback Runnable on 146 * the Message that is returned. 147 * @param h Handler to assign to the returned Message object's <em>target</em> member. 148 * @param callback Runnable that will execute when the message is handled. 149 * @return A Message object from the global pool. 150 */ 151 public static Message obtain(Handler h, Runnable callback) { 152 Message m = obtain(); 153 m.target = h; 154 m.callback = callback; 155 156 return m; 157 } 158 159 /** 160 * Same as {@link #obtain()}, but sets the values for both <em>target</em> and 161 * <em>what</em> members on the Message. 162 * @param h Value to assign to the <em>target</em> member. 163 * @param what Value to assign to the <em>what</em> member. 164 * @return A Message object from the global pool. 165 */ 166 public static Message obtain(Handler h, int what) { 167 Message m = obtain(); 168 m.target = h; 169 m.what = what; 170 171 return m; 172 } 173 174 /** 175 * Same as {@link #obtain()}, but sets the values of the <em>target</em>, <em>what</em>, and <em>obj</em> 176 * members. 177 * @param h The <em>target</em> value to set. 178 * @param what The <em>what</em> value to set. 179 * @param obj The <em>object</em> method to set. 180 * @return A Message object from the global pool. 181 */ 182 public static Message obtain(Handler h, int what, Object obj) { 183 Message m = obtain(); 184 m.target = h; 185 m.what = what; 186 m.obj = obj; 187 188 return m; 189 } 190 191 /** 192 * Same as {@link #obtain()}, but sets the values of the <em>target</em>, <em>what</em>, 193 * <em>arg1</em>, and <em>arg2</em> members. 194 * 195 * @param h The <em>target</em> value to set. 196 * @param what The <em>what</em> value to set. 197 * @param arg1 The <em>arg1</em> value to set. 198 * @param arg2 The <em>arg2</em> value to set. 199 * @return A Message object from the global pool. 200 */ 201 public static Message obtain(Handler h, int what, int arg1, int arg2) { 202 Message m = obtain(); 203 m.target = h; 204 m.what = what; 205 m.arg1 = arg1; 206 m.arg2 = arg2; 207 208 return m; 209 } 210 211 /** 212 * Same as {@link #obtain()}, but sets the values of the <em>target</em>, <em>what</em>, 213 * <em>arg1</em>, <em>arg2</em>, and <em>obj</em> members. 214 * 215 * @param h The <em>target</em> value to set. 216 * @param what The <em>what</em> value to set. 217 * @param arg1 The <em>arg1</em> value to set. 218 * @param arg2 The <em>arg2</em> value to set. 219 * @param obj The <em>obj</em> value to set. 220 * @return A Message object from the global pool. 221 */ 222 public static Message obtain(Handler h, int what, 223 int arg1, int arg2, Object obj) { 224 Message m = obtain(); 225 m.target = h; 226 m.what = what; 227 m.arg1 = arg1; 228 m.arg2 = arg2; 229 m.obj = obj; 230 231 return m; 232 } 233 234 /** 235 * Return a Message instance to the global pool. You MUST NOT touch 236 * the Message after calling this function -- it has effectively been 237 * freed. 238 */ 239 public void recycle() { 240 synchronized (mPoolSync) { 241 if (mPoolSize < MAX_POOL_SIZE) { 242 clearForRecycle(); 243 244 next = mPool; 245 mPool = this; 246 } 247 } 248 } 249 250 /** 251 * Make this message like o. Performs a shallow copy of the data field. 252 * Does not copy the linked list fields, nor the timestamp or 253 * target/callback of the original message. 254 */ 255 public void copyFrom(Message o) { 256 this.what = o.what; 257 this.arg1 = o.arg1; 258 this.arg2 = o.arg2; 259 this.obj = o.obj; 260 this.replyTo = o.replyTo; 261 262 if (o.data != null) { 263 this.data = (Bundle) o.data.clone(); 264 } else { 265 this.data = null; 266 } 267 } 268 269 /** 270 * Return the targeted delivery time of this message, in milliseconds. 271 */ 272 public long getWhen() { 273 return when; 274 } 275 276 public void setTarget(Handler target) { 277 this.target = target; 278 } 279 280 /** 281 * Retrieve the a {@link android.os.Handler Handler} implementation that 282 * will receive this message. The object must implement 283 * {@link android.os.Handler#handleMessage(android.os.Message) 284 * Handler.handleMessage()}. Each Handler has its own name-space for 285 * message codes, so you do not need to 286 * worry about yours conflicting with other handlers. 287 */ 288 public Handler getTarget() { 289 return target; 290 } 291 292 /** 293 * Retrieve callback object that will execute when this message is handled. 294 * This object must implement Runnable. This is called by 295 * the <em>target</em> {@link Handler} that is receiving this Message to 296 * dispatch it. If 297 * not set, the message will be dispatched to the receiving Handler's 298 * {@link Handler#handleMessage(Message Handler.handleMessage())}. 299 */ 300 public Runnable getCallback() { 301 return callback; 302 } 303 304 /** 305 * Obtains a Bundle of arbitrary data associated with this 306 * event, lazily creating it if necessary. Set this value by calling 307 * {@link #setData(Bundle)}. Note that when transferring data across 308 * processes via {@link Messenger}, you will need to set your ClassLoader 309 * on the Bundle via {@link Bundle#setClassLoader(ClassLoader) 310 * Bundle.setClassLoader()} so that it can instantiate your objects when 311 * you retrieve them. 312 * @see #peekData() 313 * @see #setData(Bundle) 314 */ 315 public Bundle getData() { 316 if (data == null) { 317 data = new Bundle(); 318 } 319 320 return data; 321 } 322 323 /** 324 * Like getData(), but does not lazily create the Bundle. A null 325 * is returned if the Bundle does not already exist. See 326 * {@link #getData} for further information on this. 327 * @see #getData() 328 * @see #setData(Bundle) 329 */ 330 public Bundle peekData() { 331 return data; 332 } 333 334 /** 335 * Sets a Bundle of arbitrary data values. Use arg1 and arg1 members 336 * as a lower cost way to send a few simple integer values, if you can. 337 * @see #getData() 338 * @see #peekData() 339 */ 340 public void setData(Bundle data) { 341 this.data = data; 342 } 343 344 /** 345 * Sends this Message to the Handler specified by {@link #getTarget}. 346 * Throws a null pointer exception if this field has not been set. 347 */ 348 public void sendToTarget() { 349 target.sendMessage(this); 350 } 351 352 /*package*/ void clearForRecycle() { 353 what = 0; 354 arg1 = 0; 355 arg2 = 0; 356 obj = null; 357 replyTo = null; 358 when = 0; 359 target = null; 360 callback = null; 361 data = null; 362 } 363 364 /** Constructor (but the preferred way to get a Message is to call {@link #obtain() Message.obtain()}). 365 */ 366 public Message() { 367 } 368 369 public String toString() { 370 return toString(SystemClock.uptimeMillis()); 371 } 372 373 String toString(long now) { 374 StringBuilder b = new StringBuilder(); 375 376 b.append("{ what="); 377 b.append(what); 378 379 b.append(" when="); 380 TimeUtils.formatDuration(when-now, b); 381 382 if (arg1 != 0) { 383 b.append(" arg1="); 384 b.append(arg1); 385 } 386 387 if (arg2 != 0) { 388 b.append(" arg2="); 389 b.append(arg2); 390 } 391 392 if (obj != null) { 393 b.append(" obj="); 394 b.append(obj); 395 } 396 397 b.append(" }"); 398 399 return b.toString(); 400 } 401 402 public static final Parcelable.Creator<Message> CREATOR 403 = new Parcelable.Creator<Message>() { 404 public Message createFromParcel(Parcel source) { 405 Message msg = Message.obtain(); 406 msg.readFromParcel(source); 407 return msg; 408 } 409 410 public Message[] newArray(int size) { 411 return new Message[size]; 412 } 413 }; 414 415 public int describeContents() { 416 return 0; 417 } 418 419 public void writeToParcel(Parcel dest, int flags) { 420 if (callback != null) { 421 throw new RuntimeException( 422 "Can't marshal callbacks across processes."); 423 } 424 dest.writeInt(what); 425 dest.writeInt(arg1); 426 dest.writeInt(arg2); 427 if (obj != null) { 428 try { 429 Parcelable p = (Parcelable)obj; 430 dest.writeInt(1); 431 dest.writeParcelable(p, flags); 432 } catch (ClassCastException e) { 433 throw new RuntimeException( 434 "Can't marshal non-Parcelable objects across processes."); 435 } 436 } else { 437 dest.writeInt(0); 438 } 439 dest.writeLong(when); 440 dest.writeBundle(data); 441 Messenger.writeMessengerOrNullToParcel(replyTo, dest); 442 } 443 444 private final void readFromParcel(Parcel source) { 445 what = source.readInt(); 446 arg1 = source.readInt(); 447 arg2 = source.readInt(); 448 if (source.readInt() != 0) { 449 obj = source.readParcelable(getClass().getClassLoader()); 450 } 451 when = source.readLong(); 452 data = source.readBundle(); 453 replyTo = Messenger.readMessengerOrNullFromParcel(source); 454 } 455 } 456 457