AsyncTask.java revision 44bc07d8740058398d4009615681120168673dd8
1/* 2 * Copyright (C) 2008 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 java.util.ArrayDeque; 20import java.util.concurrent.BlockingQueue; 21import java.util.concurrent.Callable; 22import java.util.concurrent.CancellationException; 23import java.util.concurrent.Executor; 24import java.util.concurrent.ExecutionException; 25import java.util.concurrent.FutureTask; 26import java.util.concurrent.LinkedBlockingQueue; 27import java.util.concurrent.ThreadFactory; 28import java.util.concurrent.ThreadPoolExecutor; 29import java.util.concurrent.TimeUnit; 30import java.util.concurrent.TimeoutException; 31import java.util.concurrent.atomic.AtomicBoolean; 32import java.util.concurrent.atomic.AtomicInteger; 33 34/** 35 * <p>AsyncTask enables proper and easy use of the UI thread. This class allows to 36 * perform background operations and publish results on the UI thread without 37 * having to manipulate threads and/or handlers.</p> 38 * 39 * <p>AsyncTask is designed to be a helper class around {@link Thread} and {@link Handler} 40 * and does not constitute a generic threading framework. AsyncTasks should ideally be 41 * used for short operations (a few seconds at the most.) If you need to keep threads 42 * running for long periods of time, it is highly recommended you use the various APIs 43 * provided by the <code>java.util.concurrent</code> package such as {@link Executor}, 44 * {@link ThreadPoolExecutor} and {@link FutureTask}.</p> 45 * 46 * <p>An asynchronous task is defined by a computation that runs on a background thread and 47 * whose result is published on the UI thread. An asynchronous task is defined by 3 generic 48 * types, called <code>Params</code>, <code>Progress</code> and <code>Result</code>, 49 * and 4 steps, called <code>onPreExecute</code>, <code>doInBackground</code>, 50 * <code>onProgressUpdate</code> and <code>onPostExecute</code>.</p> 51 * 52 * <div class="special reference"> 53 * <h3>Developer Guides</h3> 54 * <p>For more information about using tasks and threads, read the 55 * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html">Processes and 56 * Threads</a> developer guide.</p> 57 * </div> 58 * 59 * <h2>Usage</h2> 60 * <p>AsyncTask must be subclassed to be used. The subclass will override at least 61 * one method ({@link #doInBackground}), and most often will override a 62 * second one ({@link #onPostExecute}.)</p> 63 * 64 * <p>Here is an example of subclassing:</p> 65 * <pre class="prettyprint"> 66 * private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> { 67 * protected Long doInBackground(URL... urls) { 68 * int count = urls.length; 69 * long totalSize = 0; 70 * for (int i = 0; i < count; i++) { 71 * totalSize += Downloader.downloadFile(urls[i]); 72 * publishProgress((int) ((i / (float) count) * 100)); 73 * // Escape early if cancel() is called 74 * if (isCancelled()) break; 75 * } 76 * return totalSize; 77 * } 78 * 79 * protected void onProgressUpdate(Integer... progress) { 80 * setProgressPercent(progress[0]); 81 * } 82 * 83 * protected void onPostExecute(Long result) { 84 * showDialog("Downloaded " + result + " bytes"); 85 * } 86 * } 87 * </pre> 88 * 89 * <p>Once created, a task is executed very simply:</p> 90 * <pre class="prettyprint"> 91 * new DownloadFilesTask().execute(url1, url2, url3); 92 * </pre> 93 * 94 * <h2>AsyncTask's generic types</h2> 95 * <p>The three types used by an asynchronous task are the following:</p> 96 * <ol> 97 * <li><code>Params</code>, the type of the parameters sent to the task upon 98 * execution.</li> 99 * <li><code>Progress</code>, the type of the progress units published during 100 * the background computation.</li> 101 * <li><code>Result</code>, the type of the result of the background 102 * computation.</li> 103 * </ol> 104 * <p>Not all types are always used by an asynchronous task. To mark a type as unused, 105 * simply use the type {@link Void}:</p> 106 * <pre> 107 * private class MyTask extends AsyncTask<Void, Void, Void> { ... } 108 * </pre> 109 * 110 * <h2>The 4 steps</h2> 111 * <p>When an asynchronous task is executed, the task goes through 4 steps:</p> 112 * <ol> 113 * <li>{@link #onPreExecute()}, invoked on the UI thread before the task 114 * is executed. This step is normally used to setup the task, for instance by 115 * showing a progress bar in the user interface.</li> 116 * <li>{@link #doInBackground}, invoked on the background thread 117 * immediately after {@link #onPreExecute()} finishes executing. This step is used 118 * to perform background computation that can take a long time. The parameters 119 * of the asynchronous task are passed to this step. The result of the computation must 120 * be returned by this step and will be passed back to the last step. This step 121 * can also use {@link #publishProgress} to publish one or more units 122 * of progress. These values are published on the UI thread, in the 123 * {@link #onProgressUpdate} step.</li> 124 * <li>{@link #onProgressUpdate}, invoked on the UI thread after a 125 * call to {@link #publishProgress}. The timing of the execution is 126 * undefined. This method is used to display any form of progress in the user 127 * interface while the background computation is still executing. For instance, 128 * it can be used to animate a progress bar or show logs in a text field.</li> 129 * <li>{@link #onPostExecute}, invoked on the UI thread after the background 130 * computation finishes. The result of the background computation is passed to 131 * this step as a parameter.</li> 132 * </ol> 133 * 134 * <h2>Cancelling a task</h2> 135 * <p>A task can be cancelled at any time by invoking {@link #cancel(boolean)}. Invoking 136 * this method will cause subsequent calls to {@link #isCancelled()} to return true. 137 * After invoking this method, {@link #onCancelled(Object)}, instead of 138 * {@link #onPostExecute(Object)} will be invoked after {@link #doInBackground(Object[])} 139 * returns. To ensure that a task is cancelled as quickly as possible, you should always 140 * check the return value of {@link #isCancelled()} periodically from 141 * {@link #doInBackground(Object[])}, if possible (inside a loop for instance.)</p> 142 * 143 * <h2>Threading rules</h2> 144 * <p>There are a few threading rules that must be followed for this class to 145 * work properly:</p> 146 * <ul> 147 * <li>The AsyncTask class must be loaded on the UI thread. This is done 148 * automatically as of {@link android.os.Build.VERSION_CODES#JELLY_BEAN}.</li> 149 * <li>The task instance must be created on the UI thread.</li> 150 * <li>{@link #execute} must be invoked on the UI thread.</li> 151 * <li>Do not call {@link #onPreExecute()}, {@link #onPostExecute}, 152 * {@link #doInBackground}, {@link #onProgressUpdate} manually.</li> 153 * <li>The task can be executed only once (an exception will be thrown if 154 * a second execution is attempted.)</li> 155 * </ul> 156 * 157 * <h2>Memory observability</h2> 158 * <p>AsyncTask guarantees that all callback calls are synchronized in such a way that the following 159 * operations are safe without explicit synchronizations.</p> 160 * <ul> 161 * <li>Set member fields in the constructor or {@link #onPreExecute}, and refer to them 162 * in {@link #doInBackground}. 163 * <li>Set member fields in {@link #doInBackground}, and refer to them in 164 * {@link #onProgressUpdate} and {@link #onPostExecute}. 165 * </ul> 166 * 167 * <h2>Order of execution</h2> 168 * <p>When first introduced, AsyncTasks were executed serially on a single background 169 * thread. Starting with {@link android.os.Build.VERSION_CODES#DONUT}, this was changed 170 * to a pool of threads allowing multiple tasks to operate in parallel. Starting with 171 * {@link android.os.Build.VERSION_CODES#HONEYCOMB}, tasks are executed on a single 172 * thread to avoid common application errors caused by parallel execution.</p> 173 * <p>If you truly want parallel execution, you can invoke 174 * {@link #executeOnExecutor(java.util.concurrent.Executor, Object[])} with 175 * {@link #THREAD_POOL_EXECUTOR}.</p> 176 */ 177public abstract class AsyncTask<Params, Progress, Result> { 178 private static final String LOG_TAG = "AsyncTask"; 179 180 private static final int CPU_COUNT = Runtime.getRuntime().availableProcessors(); 181 private static final int CORE_POOL_SIZE = CPU_COUNT + 1; 182 private static final int MAXIMUM_POOL_SIZE = CPU_COUNT * 2 + 1; 183 private static final int KEEP_ALIVE = 1; 184 185 private static final ThreadFactory sThreadFactory = new ThreadFactory() { 186 private final AtomicInteger mCount = new AtomicInteger(1); 187 188 public Thread newThread(Runnable r) { 189 return new Thread(r, "AsyncTask #" + mCount.getAndIncrement()); 190 } 191 }; 192 193 private static final BlockingQueue<Runnable> sPoolWorkQueue = 194 new LinkedBlockingQueue<Runnable>(128); 195 196 /** 197 * An {@link Executor} that can be used to execute tasks in parallel. 198 */ 199 public static final Executor THREAD_POOL_EXECUTOR 200 = new ThreadPoolExecutor(CORE_POOL_SIZE, MAXIMUM_POOL_SIZE, KEEP_ALIVE, 201 TimeUnit.SECONDS, sPoolWorkQueue, sThreadFactory); 202 203 /** 204 * An {@link Executor} that executes tasks one at a time in serial 205 * order. This serialization is global to a particular process. 206 */ 207 public static final Executor SERIAL_EXECUTOR = new SerialExecutor(); 208 209 private static final int MESSAGE_POST_RESULT = 0x1; 210 private static final int MESSAGE_POST_PROGRESS = 0x2; 211 212 private static volatile Executor sDefaultExecutor = SERIAL_EXECUTOR; 213 private static InternalHandler sHandler; 214 215 private final WorkerRunnable<Params, Result> mWorker; 216 private final FutureTask<Result> mFuture; 217 218 private volatile Status mStatus = Status.PENDING; 219 220 private final AtomicBoolean mCancelled = new AtomicBoolean(); 221 private final AtomicBoolean mTaskInvoked = new AtomicBoolean(); 222 223 private static class SerialExecutor implements Executor { 224 final ArrayDeque<Runnable> mTasks = new ArrayDeque<Runnable>(); 225 Runnable mActive; 226 227 public synchronized void execute(final Runnable r) { 228 mTasks.offer(new Runnable() { 229 public void run() { 230 try { 231 r.run(); 232 } finally { 233 scheduleNext(); 234 } 235 } 236 }); 237 if (mActive == null) { 238 scheduleNext(); 239 } 240 } 241 242 protected synchronized void scheduleNext() { 243 if ((mActive = mTasks.poll()) != null) { 244 THREAD_POOL_EXECUTOR.execute(mActive); 245 } 246 } 247 } 248 249 /** 250 * Indicates the current status of the task. Each status will be set only once 251 * during the lifetime of a task. 252 */ 253 public enum Status { 254 /** 255 * Indicates that the task has not been executed yet. 256 */ 257 PENDING, 258 /** 259 * Indicates that the task is running. 260 */ 261 RUNNING, 262 /** 263 * Indicates that {@link AsyncTask#onPostExecute} has finished. 264 */ 265 FINISHED, 266 } 267 268 private static Handler getHandler() { 269 synchronized (AsyncTask.class) { 270 if (sHandler == null) { 271 sHandler = new InternalHandler(); 272 } 273 return sHandler; 274 } 275 } 276 277 /** @hide */ 278 public static void setDefaultExecutor(Executor exec) { 279 sDefaultExecutor = exec; 280 } 281 282 /** 283 * Creates a new asynchronous task. This constructor must be invoked on the UI thread. 284 */ 285 public AsyncTask() { 286 mWorker = new WorkerRunnable<Params, Result>() { 287 public Result call() throws Exception { 288 mTaskInvoked.set(true); 289 290 Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); 291 //noinspection unchecked 292 return postResult(doInBackground(mParams)); 293 } 294 }; 295 296 mFuture = new FutureTask<Result>(mWorker) { 297 @Override 298 protected void done() { 299 try { 300 postResultIfNotInvoked(get()); 301 } catch (InterruptedException e) { 302 android.util.Log.w(LOG_TAG, e); 303 } catch (ExecutionException e) { 304 throw new RuntimeException("An error occurred while executing doInBackground()", 305 e.getCause()); 306 } catch (CancellationException e) { 307 postResultIfNotInvoked(null); 308 } 309 } 310 }; 311 } 312 313 private void postResultIfNotInvoked(Result result) { 314 final boolean wasTaskInvoked = mTaskInvoked.get(); 315 if (!wasTaskInvoked) { 316 postResult(result); 317 } 318 } 319 320 private Result postResult(Result result) { 321 @SuppressWarnings("unchecked") 322 Message message = getHandler().obtainMessage(MESSAGE_POST_RESULT, 323 new AsyncTaskResult<Result>(this, result)); 324 message.sendToTarget(); 325 return result; 326 } 327 328 /** 329 * Returns the current status of this task. 330 * 331 * @return The current status. 332 */ 333 public final Status getStatus() { 334 return mStatus; 335 } 336 337 /** 338 * Override this method to perform a computation on a background thread. The 339 * specified parameters are the parameters passed to {@link #execute} 340 * by the caller of this task. 341 * 342 * This method can call {@link #publishProgress} to publish updates 343 * on the UI thread. 344 * 345 * @param params The parameters of the task. 346 * 347 * @return A result, defined by the subclass of this task. 348 * 349 * @see #onPreExecute() 350 * @see #onPostExecute 351 * @see #publishProgress 352 */ 353 protected abstract Result doInBackground(Params... params); 354 355 /** 356 * Runs on the UI thread before {@link #doInBackground}. 357 * 358 * @see #onPostExecute 359 * @see #doInBackground 360 */ 361 protected void onPreExecute() { 362 } 363 364 /** 365 * <p>Runs on the UI thread after {@link #doInBackground}. The 366 * specified result is the value returned by {@link #doInBackground}.</p> 367 * 368 * <p>This method won't be invoked if the task was cancelled.</p> 369 * 370 * @param result The result of the operation computed by {@link #doInBackground}. 371 * 372 * @see #onPreExecute 373 * @see #doInBackground 374 * @see #onCancelled(Object) 375 */ 376 @SuppressWarnings({"UnusedDeclaration"}) 377 protected void onPostExecute(Result result) { 378 } 379 380 /** 381 * Runs on the UI thread after {@link #publishProgress} is invoked. 382 * The specified values are the values passed to {@link #publishProgress}. 383 * 384 * @param values The values indicating progress. 385 * 386 * @see #publishProgress 387 * @see #doInBackground 388 */ 389 @SuppressWarnings({"UnusedDeclaration"}) 390 protected void onProgressUpdate(Progress... values) { 391 } 392 393 /** 394 * <p>Runs on the UI thread after {@link #cancel(boolean)} is invoked and 395 * {@link #doInBackground(Object[])} has finished.</p> 396 * 397 * <p>The default implementation simply invokes {@link #onCancelled()} and 398 * ignores the result. If you write your own implementation, do not call 399 * <code>super.onCancelled(result)</code>.</p> 400 * 401 * @param result The result, if any, computed in 402 * {@link #doInBackground(Object[])}, can be null 403 * 404 * @see #cancel(boolean) 405 * @see #isCancelled() 406 */ 407 @SuppressWarnings({"UnusedParameters"}) 408 protected void onCancelled(Result result) { 409 onCancelled(); 410 } 411 412 /** 413 * <p>Applications should preferably override {@link #onCancelled(Object)}. 414 * This method is invoked by the default implementation of 415 * {@link #onCancelled(Object)}.</p> 416 * 417 * <p>Runs on the UI thread after {@link #cancel(boolean)} is invoked and 418 * {@link #doInBackground(Object[])} has finished.</p> 419 * 420 * @see #onCancelled(Object) 421 * @see #cancel(boolean) 422 * @see #isCancelled() 423 */ 424 protected void onCancelled() { 425 } 426 427 /** 428 * Returns <tt>true</tt> if this task was cancelled before it completed 429 * normally. If you are calling {@link #cancel(boolean)} on the task, 430 * the value returned by this method should be checked periodically from 431 * {@link #doInBackground(Object[])} to end the task as soon as possible. 432 * 433 * @return <tt>true</tt> if task was cancelled before it completed 434 * 435 * @see #cancel(boolean) 436 */ 437 public final boolean isCancelled() { 438 return mCancelled.get(); 439 } 440 441 /** 442 * <p>Attempts to cancel execution of this task. This attempt will 443 * fail if the task has already completed, already been cancelled, 444 * or could not be cancelled for some other reason. If successful, 445 * and this task has not started when <tt>cancel</tt> is called, 446 * this task should never run. If the task has already started, 447 * then the <tt>mayInterruptIfRunning</tt> parameter determines 448 * whether the thread executing this task should be interrupted in 449 * an attempt to stop the task.</p> 450 * 451 * <p>Calling this method will result in {@link #onCancelled(Object)} being 452 * invoked on the UI thread after {@link #doInBackground(Object[])} 453 * returns. Calling this method guarantees that {@link #onPostExecute(Object)} 454 * is never invoked. After invoking this method, you should check the 455 * value returned by {@link #isCancelled()} periodically from 456 * {@link #doInBackground(Object[])} to finish the task as early as 457 * possible.</p> 458 * 459 * @param mayInterruptIfRunning <tt>true</tt> if the thread executing this 460 * task should be interrupted; otherwise, in-progress tasks are allowed 461 * to complete. 462 * 463 * @return <tt>false</tt> if the task could not be cancelled, 464 * typically because it has already completed normally; 465 * <tt>true</tt> otherwise 466 * 467 * @see #isCancelled() 468 * @see #onCancelled(Object) 469 */ 470 public final boolean cancel(boolean mayInterruptIfRunning) { 471 mCancelled.set(true); 472 return mFuture.cancel(mayInterruptIfRunning); 473 } 474 475 /** 476 * Waits if necessary for the computation to complete, and then 477 * retrieves its result. 478 * 479 * @return The computed result. 480 * 481 * @throws CancellationException If the computation was cancelled. 482 * @throws ExecutionException If the computation threw an exception. 483 * @throws InterruptedException If the current thread was interrupted 484 * while waiting. 485 */ 486 public final Result get() throws InterruptedException, ExecutionException { 487 return mFuture.get(); 488 } 489 490 /** 491 * Waits if necessary for at most the given time for the computation 492 * to complete, and then retrieves its result. 493 * 494 * @param timeout Time to wait before cancelling the operation. 495 * @param unit The time unit for the timeout. 496 * 497 * @return The computed result. 498 * 499 * @throws CancellationException If the computation was cancelled. 500 * @throws ExecutionException If the computation threw an exception. 501 * @throws InterruptedException If the current thread was interrupted 502 * while waiting. 503 * @throws TimeoutException If the wait timed out. 504 */ 505 public final Result get(long timeout, TimeUnit unit) throws InterruptedException, 506 ExecutionException, TimeoutException { 507 return mFuture.get(timeout, unit); 508 } 509 510 /** 511 * Executes the task with the specified parameters. The task returns 512 * itself (this) so that the caller can keep a reference to it. 513 * 514 * <p>Note: this function schedules the task on a queue for a single background 515 * thread or pool of threads depending on the platform version. When first 516 * introduced, AsyncTasks were executed serially on a single background thread. 517 * Starting with {@link android.os.Build.VERSION_CODES#DONUT}, this was changed 518 * to a pool of threads allowing multiple tasks to operate in parallel. Starting 519 * {@link android.os.Build.VERSION_CODES#HONEYCOMB}, tasks are back to being 520 * executed on a single thread to avoid common application errors caused 521 * by parallel execution. If you truly want parallel execution, you can use 522 * the {@link #executeOnExecutor} version of this method 523 * with {@link #THREAD_POOL_EXECUTOR}; however, see commentary there for warnings 524 * on its use. 525 * 526 * <p>This method must be invoked on the UI thread. 527 * 528 * @param params The parameters of the task. 529 * 530 * @return This instance of AsyncTask. 531 * 532 * @throws IllegalStateException If {@link #getStatus()} returns either 533 * {@link AsyncTask.Status#RUNNING} or {@link AsyncTask.Status#FINISHED}. 534 * 535 * @see #executeOnExecutor(java.util.concurrent.Executor, Object[]) 536 * @see #execute(Runnable) 537 */ 538 public final AsyncTask<Params, Progress, Result> execute(Params... params) { 539 return executeOnExecutor(sDefaultExecutor, params); 540 } 541 542 /** 543 * Executes the task with the specified parameters. The task returns 544 * itself (this) so that the caller can keep a reference to it. 545 * 546 * <p>This method is typically used with {@link #THREAD_POOL_EXECUTOR} to 547 * allow multiple tasks to run in parallel on a pool of threads managed by 548 * AsyncTask, however you can also use your own {@link Executor} for custom 549 * behavior. 550 * 551 * <p><em>Warning:</em> Allowing multiple tasks to run in parallel from 552 * a thread pool is generally <em>not</em> what one wants, because the order 553 * of their operation is not defined. For example, if these tasks are used 554 * to modify any state in common (such as writing a file due to a button click), 555 * there are no guarantees on the order of the modifications. 556 * Without careful work it is possible in rare cases for the newer version 557 * of the data to be over-written by an older one, leading to obscure data 558 * loss and stability issues. Such changes are best 559 * executed in serial; to guarantee such work is serialized regardless of 560 * platform version you can use this function with {@link #SERIAL_EXECUTOR}. 561 * 562 * <p>This method must be invoked on the UI thread. 563 * 564 * @param exec The executor to use. {@link #THREAD_POOL_EXECUTOR} is available as a 565 * convenient process-wide thread pool for tasks that are loosely coupled. 566 * @param params The parameters of the task. 567 * 568 * @return This instance of AsyncTask. 569 * 570 * @throws IllegalStateException If {@link #getStatus()} returns either 571 * {@link AsyncTask.Status#RUNNING} or {@link AsyncTask.Status#FINISHED}. 572 * 573 * @see #execute(Object[]) 574 */ 575 public final AsyncTask<Params, Progress, Result> executeOnExecutor(Executor exec, 576 Params... params) { 577 if (mStatus != Status.PENDING) { 578 switch (mStatus) { 579 case RUNNING: 580 throw new IllegalStateException("Cannot execute task:" 581 + " the task is already running."); 582 case FINISHED: 583 throw new IllegalStateException("Cannot execute task:" 584 + " the task has already been executed " 585 + "(a task can be executed only once)"); 586 } 587 } 588 589 mStatus = Status.RUNNING; 590 591 onPreExecute(); 592 593 mWorker.mParams = params; 594 exec.execute(mFuture); 595 596 return this; 597 } 598 599 /** 600 * Convenience version of {@link #execute(Object...)} for use with 601 * a simple Runnable object. See {@link #execute(Object[])} for more 602 * information on the order of execution. 603 * 604 * @see #execute(Object[]) 605 * @see #executeOnExecutor(java.util.concurrent.Executor, Object[]) 606 */ 607 public static void execute(Runnable runnable) { 608 sDefaultExecutor.execute(runnable); 609 } 610 611 /** 612 * This method can be invoked from {@link #doInBackground} to 613 * publish updates on the UI thread while the background computation is 614 * still running. Each call to this method will trigger the execution of 615 * {@link #onProgressUpdate} on the UI thread. 616 * 617 * {@link #onProgressUpdate} will not be called if the task has been 618 * canceled. 619 * 620 * @param values The progress values to update the UI with. 621 * 622 * @see #onProgressUpdate 623 * @see #doInBackground 624 */ 625 protected final void publishProgress(Progress... values) { 626 if (!isCancelled()) { 627 getHandler().obtainMessage(MESSAGE_POST_PROGRESS, 628 new AsyncTaskResult<Progress>(this, values)).sendToTarget(); 629 } 630 } 631 632 private void finish(Result result) { 633 if (isCancelled()) { 634 onCancelled(result); 635 } else { 636 onPostExecute(result); 637 } 638 mStatus = Status.FINISHED; 639 } 640 641 private static class InternalHandler extends Handler { 642 public InternalHandler() { 643 super(Looper.getMainLooper()); 644 } 645 646 @SuppressWarnings({"unchecked", "RawUseOfParameterizedType"}) 647 @Override 648 public void handleMessage(Message msg) { 649 AsyncTaskResult<?> result = (AsyncTaskResult<?>) msg.obj; 650 switch (msg.what) { 651 case MESSAGE_POST_RESULT: 652 // There is only one result 653 result.mTask.finish(result.mData[0]); 654 break; 655 case MESSAGE_POST_PROGRESS: 656 result.mTask.onProgressUpdate(result.mData); 657 break; 658 } 659 } 660 } 661 662 private static abstract class WorkerRunnable<Params, Result> implements Callable<Result> { 663 Params[] mParams; 664 } 665 666 @SuppressWarnings({"RawUseOfParameterizedType"}) 667 private static class AsyncTaskResult<Data> { 668 final AsyncTask mTask; 669 final Data[] mData; 670 671 AsyncTaskResult(AsyncTask task, Data... data) { 672 mTask = task; 673 mData = data; 674 } 675 } 676} 677