| /* |
| * Copyright (C) 2008 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package android.os; |
| |
| import java.util.ArrayDeque; |
| import java.util.concurrent.BlockingQueue; |
| import java.util.concurrent.Callable; |
| import java.util.concurrent.CancellationException; |
| import java.util.concurrent.Executor; |
| import java.util.concurrent.ExecutionException; |
| import java.util.concurrent.FutureTask; |
| import java.util.concurrent.LinkedBlockingQueue; |
| import java.util.concurrent.ThreadFactory; |
| import java.util.concurrent.ThreadPoolExecutor; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.TimeoutException; |
| import java.util.concurrent.atomic.AtomicBoolean; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| /** |
| * <p>AsyncTask enables proper and easy use of the UI thread. This class allows to |
| * perform background operations and publish results on the UI thread without |
| * having to manipulate threads and/or handlers.</p> |
| * |
| * <p>An asynchronous task is defined by a computation that runs on a background thread and |
| * whose result is published on the UI thread. An asynchronous task is defined by 3 generic |
| * types, called <code>Params</code>, <code>Progress</code> and <code>Result</code>, |
| * and 4 steps, called <code>onPreExecute</code>, <code>doInBackground</code>, |
| * <code>onProgressUpdate</code> and <code>onPostExecute</code>.</p> |
| * |
| * <div class="special reference"> |
| * <h3>Developer Guides</h3> |
| * <p>For more information about using tasks and threads, read the |
| * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html">Processes and |
| * Threads</a> developer guide.</p> |
| * </div> |
| * |
| * <h2>Usage</h2> |
| * <p>AsyncTask must be subclassed to be used. The subclass will override at least |
| * one method ({@link #doInBackground}), and most often will override a |
| * second one ({@link #onPostExecute}.)</p> |
| * |
| * <p>Here is an example of subclassing:</p> |
| * <pre class="prettyprint"> |
| * private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> { |
| * protected Long doInBackground(URL... urls) { |
| * int count = urls.length; |
| * long totalSize = 0; |
| * for (int i = 0; i < count; i++) { |
| * totalSize += Downloader.downloadFile(urls[i]); |
| * publishProgress((int) ((i / (float) count) * 100)); |
| * } |
| * return totalSize; |
| * } |
| * |
| * protected void onProgressUpdate(Integer... progress) { |
| * setProgressPercent(progress[0]); |
| * } |
| * |
| * protected void onPostExecute(Long result) { |
| * showDialog("Downloaded " + result + " bytes"); |
| * } |
| * } |
| * </pre> |
| * |
| * <p>Once created, a task is executed very simply:</p> |
| * <pre class="prettyprint"> |
| * new DownloadFilesTask().execute(url1, url2, url3); |
| * </pre> |
| * |
| * <h2>AsyncTask's generic types</h2> |
| * <p>The three types used by an asynchronous task are the following:</p> |
| * <ol> |
| * <li><code>Params</code>, the type of the parameters sent to the task upon |
| * execution.</li> |
| * <li><code>Progress</code>, the type of the progress units published during |
| * the background computation.</li> |
| * <li><code>Result</code>, the type of the result of the background |
| * computation.</li> |
| * </ol> |
| * <p>Not all types are always used by an asynchronous task. To mark a type as unused, |
| * simply use the type {@link Void}:</p> |
| * <pre> |
| * private class MyTask extends AsyncTask<Void, Void, Void> { ... } |
| * </pre> |
| * |
| * <h2>The 4 steps</h2> |
| * <p>When an asynchronous task is executed, the task goes through 4 steps:</p> |
| * <ol> |
| * <li>{@link #onPreExecute()}, invoked on the UI thread immediately after the task |
| * is executed. This step is normally used to setup the task, for instance by |
| * showing a progress bar in the user interface.</li> |
| * <li>{@link #doInBackground}, invoked on the background thread |
| * immediately after {@link #onPreExecute()} finishes executing. This step is used |
| * to perform background computation that can take a long time. The parameters |
| * of the asynchronous task are passed to this step. The result of the computation must |
| * be returned by this step and will be passed back to the last step. This step |
| * can also use {@link #publishProgress} to publish one or more units |
| * of progress. These values are published on the UI thread, in the |
| * {@link #onProgressUpdate} step.</li> |
| * <li>{@link #onProgressUpdate}, invoked on the UI thread after a |
| * call to {@link #publishProgress}. The timing of the execution is |
| * undefined. This method is used to display any form of progress in the user |
| * interface while the background computation is still executing. For instance, |
| * it can be used to animate a progress bar or show logs in a text field.</li> |
| * <li>{@link #onPostExecute}, invoked on the UI thread after the background |
| * computation finishes. The result of the background computation is passed to |
| * this step as a parameter.</li> |
| * </ol> |
| * |
| * <h2>Cancelling a task</h2> |
| * <p>A task can be cancelled at any time by invoking {@link #cancel(boolean)}. Invoking |
| * this method will cause subsequent calls to {@link #isCancelled()} to return true. |
| * After invoking this method, {@link #onCancelled(Object)}, instead of |
| * {@link #onPostExecute(Object)} will be invoked after {@link #doInBackground(Object[])} |
| * returns. To ensure that a task is cancelled as quickly as possible, you should always |
| * check the return value of {@link #isCancelled()} periodically from |
| * {@link #doInBackground(Object[])}, if possible (inside a loop for instance.)</p> |
| * |
| * <h2>Threading rules</h2> |
| * <p>There are a few threading rules that must be followed for this class to |
| * work properly:</p> |
| * <ul> |
| * <li>The task instance must be created on the UI thread.</li> |
| * <li>{@link #execute} must be invoked on the UI thread.</li> |
| * <li>Do not call {@link #onPreExecute()}, {@link #onPostExecute}, |
| * {@link #doInBackground}, {@link #onProgressUpdate} manually.</li> |
| * <li>The task can be executed only once (an exception will be thrown if |
| * a second execution is attempted.)</li> |
| * </ul> |
| * |
| * <h2>Memory observability</h2> |
| * <p>AsyncTask guarantees that all callback calls are synchronized in such a way that the following |
| * operations are safe without explicit synchronizations.</p> |
| * <ul> |
| * <li>Set member fields in the constructor or {@link #onPreExecute}, and refer to them |
| * in {@link #doInBackground}. |
| * <li>Set member fields in {@link #doInBackground}, and refer to them in |
| * {@link #onProgressUpdate} and {@link #onPostExecute}. |
| * </ul> |
| */ |
| public abstract class AsyncTask<Params, Progress, Result> { |
| private static final String LOG_TAG = "AsyncTask"; |
| |
| private static final int CORE_POOL_SIZE = 5; |
| private static final int MAXIMUM_POOL_SIZE = 128; |
| private static final int KEEP_ALIVE = 1; |
| |
| private static final ThreadFactory sThreadFactory = new ThreadFactory() { |
| private final AtomicInteger mCount = new AtomicInteger(1); |
| |
| public Thread newThread(Runnable r) { |
| return new Thread(r, "AsyncTask #" + mCount.getAndIncrement()); |
| } |
| }; |
| |
| private static final BlockingQueue<Runnable> sPoolWorkQueue = |
| new LinkedBlockingQueue<Runnable>(10); |
| |
| /** |
| * An {@link Executor} that can be used to execute tasks in parallel. |
| */ |
| public static final Executor THREAD_POOL_EXECUTOR |
| = new ThreadPoolExecutor(CORE_POOL_SIZE, MAXIMUM_POOL_SIZE, KEEP_ALIVE, |
| TimeUnit.SECONDS, sPoolWorkQueue, sThreadFactory); |
| |
| /** |
| * An {@link Executor} that executes tasks one at a time in serial |
| * order. This serialization is global to a particular process. |
| */ |
| public static final Executor SERIAL_EXECUTOR = new SerialExecutor(); |
| |
| private static final int MESSAGE_POST_RESULT = 0x1; |
| private static final int MESSAGE_POST_PROGRESS = 0x2; |
| |
| private static final InternalHandler sHandler = new InternalHandler(); |
| |
| private static volatile Executor sDefaultExecutor = SERIAL_EXECUTOR; |
| private final WorkerRunnable<Params, Result> mWorker; |
| private final FutureTask<Result> mFuture; |
| |
| private volatile Status mStatus = Status.PENDING; |
| |
| private final AtomicBoolean mCancelled = new AtomicBoolean(); |
| private final AtomicBoolean mTaskInvoked = new AtomicBoolean(); |
| |
| private static class SerialExecutor implements Executor { |
| final ArrayDeque<Runnable> mTasks = new ArrayDeque<Runnable>(); |
| Runnable mActive; |
| |
| public synchronized void execute(final Runnable r) { |
| mTasks.offer(new Runnable() { |
| public void run() { |
| try { |
| r.run(); |
| } finally { |
| scheduleNext(); |
| } |
| } |
| }); |
| if (mActive == null) { |
| scheduleNext(); |
| } |
| } |
| |
| protected synchronized void scheduleNext() { |
| if ((mActive = mTasks.poll()) != null) { |
| THREAD_POOL_EXECUTOR.execute(mActive); |
| } |
| } |
| } |
| |
| /** |
| * Indicates the current status of the task. Each status will be set only once |
| * during the lifetime of a task. |
| */ |
| public enum Status { |
| /** |
| * Indicates that the task has not been executed yet. |
| */ |
| PENDING, |
| /** |
| * Indicates that the task is running. |
| */ |
| RUNNING, |
| /** |
| * Indicates that {@link AsyncTask#onPostExecute} has finished. |
| */ |
| FINISHED, |
| } |
| |
| /** @hide Used to force static handler to be created. */ |
| public static void init() { |
| sHandler.getLooper(); |
| } |
| |
| /** @hide */ |
| public static void setDefaultExecutor(Executor exec) { |
| sDefaultExecutor = exec; |
| } |
| |
| /** |
| * Creates a new asynchronous task. This constructor must be invoked on the UI thread. |
| */ |
| public AsyncTask() { |
| mWorker = new WorkerRunnable<Params, Result>() { |
| public Result call() throws Exception { |
| mTaskInvoked.set(true); |
| |
| Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); |
| //noinspection unchecked |
| return postResult(doInBackground(mParams)); |
| } |
| }; |
| |
| mFuture = new FutureTask<Result>(mWorker) { |
| @Override |
| protected void done() { |
| try { |
| postResultIfNotInvoked(get()); |
| } catch (InterruptedException e) { |
| android.util.Log.w(LOG_TAG, e); |
| } catch (ExecutionException e) { |
| throw new RuntimeException("An error occured while executing doInBackground()", |
| e.getCause()); |
| } catch (CancellationException e) { |
| postResultIfNotInvoked(null); |
| } catch (Throwable t) { |
| throw new RuntimeException("An error occured while executing " |
| + "doInBackground()", t); |
| } |
| } |
| }; |
| } |
| |
| private void postResultIfNotInvoked(Result result) { |
| final boolean wasTaskInvoked = mTaskInvoked.get(); |
| if (!wasTaskInvoked) { |
| postResult(result); |
| } |
| } |
| |
| private Result postResult(Result result) { |
| @SuppressWarnings("unchecked") |
| Message message = sHandler.obtainMessage(MESSAGE_POST_RESULT, |
| new AsyncTaskResult<Result>(this, result)); |
| message.sendToTarget(); |
| return result; |
| } |
| |
| /** |
| * Returns the current status of this task. |
| * |
| * @return The current status. |
| */ |
| public final Status getStatus() { |
| return mStatus; |
| } |
| |
| /** |
| * Override this method to perform a computation on a background thread. The |
| * specified parameters are the parameters passed to {@link #execute} |
| * by the caller of this task. |
| * |
| * This method can call {@link #publishProgress} to publish updates |
| * on the UI thread. |
| * |
| * @param params The parameters of the task. |
| * |
| * @return A result, defined by the subclass of this task. |
| * |
| * @see #onPreExecute() |
| * @see #onPostExecute |
| * @see #publishProgress |
| */ |
| protected abstract Result doInBackground(Params... params); |
| |
| /** |
| * Runs on the UI thread before {@link #doInBackground}. |
| * |
| * @see #onPostExecute |
| * @see #doInBackground |
| */ |
| protected void onPreExecute() { |
| } |
| |
| /** |
| * <p>Runs on the UI thread after {@link #doInBackground}. The |
| * specified result is the value returned by {@link #doInBackground}.</p> |
| * |
| * <p>This method won't be invoked if the task was cancelled.</p> |
| * |
| * @param result The result of the operation computed by {@link #doInBackground}. |
| * |
| * @see #onPreExecute |
| * @see #doInBackground |
| * @see #onCancelled(Object) |
| */ |
| @SuppressWarnings({"UnusedDeclaration"}) |
| protected void onPostExecute(Result result) { |
| } |
| |
| /** |
| * Runs on the UI thread after {@link #publishProgress} is invoked. |
| * The specified values are the values passed to {@link #publishProgress}. |
| * |
| * @param values The values indicating progress. |
| * |
| * @see #publishProgress |
| * @see #doInBackground |
| */ |
| @SuppressWarnings({"UnusedDeclaration"}) |
| protected void onProgressUpdate(Progress... values) { |
| } |
| |
| /** |
| * <p>Runs on the UI thread after {@link #cancel(boolean)} is invoked and |
| * {@link #doInBackground(Object[])} has finished.</p> |
| * |
| * <p>The default implementation simply invokes {@link #onCancelled()} and |
| * ignores the result. If you write your own implementation, do not call |
| * <code>super.onCancelled(result)</code>.</p> |
| * |
| * @param result The result, if any, computed in |
| * {@link #doInBackground(Object[])}, can be null |
| * |
| * @see #cancel(boolean) |
| * @see #isCancelled() |
| */ |
| @SuppressWarnings({"UnusedParameters"}) |
| protected void onCancelled(Result result) { |
| onCancelled(); |
| } |
| |
| /** |
| * <p>Applications should preferably override {@link #onCancelled(Object)}. |
| * This method is invoked by the default implementation of |
| * {@link #onCancelled(Object)}.</p> |
| * |
| * <p>Runs on the UI thread after {@link #cancel(boolean)} is invoked and |
| * {@link #doInBackground(Object[])} has finished.</p> |
| * |
| * @see #onCancelled(Object) |
| * @see #cancel(boolean) |
| * @see #isCancelled() |
| */ |
| protected void onCancelled() { |
| } |
| |
| /** |
| * Returns <tt>true</tt> if this task was cancelled before it completed |
| * normally. If you are calling {@link #cancel(boolean)} on the task, |
| * the value returned by this method should be checked periodically from |
| * {@link #doInBackground(Object[])} to end the task as soon as possible. |
| * |
| * @return <tt>true</tt> if task was cancelled before it completed |
| * |
| * @see #cancel(boolean) |
| */ |
| public final boolean isCancelled() { |
| return mCancelled.get(); |
| } |
| |
| /** |
| * <p>Attempts to cancel execution of this task. This attempt will |
| * fail if the task has already completed, already been cancelled, |
| * or could not be cancelled for some other reason. If successful, |
| * and this task has not started when <tt>cancel</tt> is called, |
| * this task should never run. If the task has already started, |
| * then the <tt>mayInterruptIfRunning</tt> parameter determines |
| * whether the thread executing this task should be interrupted in |
| * an attempt to stop the task.</p> |
| * |
| * <p>Calling this method will result in {@link #onCancelled(Object)} being |
| * invoked on the UI thread after {@link #doInBackground(Object[])} |
| * returns. Calling this method guarantees that {@link #onPostExecute(Object)} |
| * is never invoked. After invoking this method, you should check the |
| * value returned by {@link #isCancelled()} periodically from |
| * {@link #doInBackground(Object[])} to finish the task as early as |
| * possible.</p> |
| * |
| * @param mayInterruptIfRunning <tt>true</tt> if the thread executing this |
| * task should be interrupted; otherwise, in-progress tasks are allowed |
| * to complete. |
| * |
| * @return <tt>false</tt> if the task could not be cancelled, |
| * typically because it has already completed normally; |
| * <tt>true</tt> otherwise |
| * |
| * @see #isCancelled() |
| * @see #onCancelled(Object) |
| */ |
| public final boolean cancel(boolean mayInterruptIfRunning) { |
| mCancelled.set(true); |
| return mFuture.cancel(mayInterruptIfRunning); |
| } |
| |
| /** |
| * Waits if necessary for the computation to complete, and then |
| * retrieves its result. |
| * |
| * @return The computed result. |
| * |
| * @throws CancellationException If the computation was cancelled. |
| * @throws ExecutionException If the computation threw an exception. |
| * @throws InterruptedException If the current thread was interrupted |
| * while waiting. |
| */ |
| public final Result get() throws InterruptedException, ExecutionException { |
| return mFuture.get(); |
| } |
| |
| /** |
| * Waits if necessary for at most the given time for the computation |
| * to complete, and then retrieves its result. |
| * |
| * @param timeout Time to wait before cancelling the operation. |
| * @param unit The time unit for the timeout. |
| * |
| * @return The computed result. |
| * |
| * @throws CancellationException If the computation was cancelled. |
| * @throws ExecutionException If the computation threw an exception. |
| * @throws InterruptedException If the current thread was interrupted |
| * while waiting. |
| * @throws TimeoutException If the wait timed out. |
| */ |
| public final Result get(long timeout, TimeUnit unit) throws InterruptedException, |
| ExecutionException, TimeoutException { |
| return mFuture.get(timeout, unit); |
| } |
| |
| /** |
| * Executes the task with the specified parameters. The task returns |
| * itself (this) so that the caller can keep a reference to it. |
| * |
| * <p>Note: this function schedules the task on a queue for a single background |
| * thread or pool of threads depending on the platform version. When first |
| * introduced, AsyncTasks were executed serially on a single background thread. |
| * Starting with {@link android.os.Build.VERSION_CODES#DONUT}, this was changed |
| * to a pool of threads allowing multiple tasks to operate in parallel. After |
| * {@link android.os.Build.VERSION_CODES#HONEYCOMB}, it is planned to change this |
| * back to a single thread to avoid common application errors caused |
| * by parallel execution. If you truly want parallel execution, you can use |
| * the {@link #executeOnExecutor} version of this method |
| * with {@link #THREAD_POOL_EXECUTOR}; however, see commentary there for warnings on |
| * its use. |
| * |
| * <p>This method must be invoked on the UI thread. |
| * |
| * @param params The parameters of the task. |
| * |
| * @return This instance of AsyncTask. |
| * |
| * @throws IllegalStateException If {@link #getStatus()} returns either |
| * {@link AsyncTask.Status#RUNNING} or {@link AsyncTask.Status#FINISHED}. |
| */ |
| public final AsyncTask<Params, Progress, Result> execute(Params... params) { |
| return executeOnExecutor(sDefaultExecutor, params); |
| } |
| |
| /** |
| * Executes the task with the specified parameters. The task returns |
| * itself (this) so that the caller can keep a reference to it. |
| * |
| * <p>This method is typically used with {@link #THREAD_POOL_EXECUTOR} to |
| * allow multiple tasks to run in parallel on a pool of threads managed by |
| * AsyncTask, however you can also use your own {@link Executor} for custom |
| * behavior. |
| * |
| * <p><em>Warning:</em> Allowing multiple tasks to run in parallel from |
| * a thread pool is generally <em>not</em> what one wants, because the order |
| * of their operation is not defined. For example, if these tasks are used |
| * to modify any state in common (such as writing a file due to a button click), |
| * there are no guarantees on the order of the modifications. |
| * Without careful work it is possible in rare cases for the newer version |
| * of the data to be over-written by an older one, leading to obscure data |
| * loss and stability issues. Such changes are best |
| * executed in serial; to guarantee such work is serialized regardless of |
| * platform version you can use this function with {@link #SERIAL_EXECUTOR}. |
| * |
| * <p>This method must be invoked on the UI thread. |
| * |
| * @param exec The executor to use. {@link #THREAD_POOL_EXECUTOR} is available as a |
| * convenient process-wide thread pool for tasks that are loosely coupled. |
| * @param params The parameters of the task. |
| * |
| * @return This instance of AsyncTask. |
| * |
| * @throws IllegalStateException If {@link #getStatus()} returns either |
| * {@link AsyncTask.Status#RUNNING} or {@link AsyncTask.Status#FINISHED}. |
| */ |
| public final AsyncTask<Params, Progress, Result> executeOnExecutor(Executor exec, |
| Params... params) { |
| if (mStatus != Status.PENDING) { |
| switch (mStatus) { |
| case RUNNING: |
| throw new IllegalStateException("Cannot execute task:" |
| + " the task is already running."); |
| case FINISHED: |
| throw new IllegalStateException("Cannot execute task:" |
| + " the task has already been executed " |
| + "(a task can be executed only once)"); |
| } |
| } |
| |
| mStatus = Status.RUNNING; |
| |
| onPreExecute(); |
| |
| mWorker.mParams = params; |
| exec.execute(mFuture); |
| |
| return this; |
| } |
| |
| /** |
| * Convenience version of {@link #execute(Object...)} for use with |
| * a simple Runnable object. |
| */ |
| public static void execute(Runnable runnable) { |
| sDefaultExecutor.execute(runnable); |
| } |
| |
| /** |
| * This method can be invoked from {@link #doInBackground} to |
| * publish updates on the UI thread while the background computation is |
| * still running. Each call to this method will trigger the execution of |
| * {@link #onProgressUpdate} on the UI thread. |
| * |
| * {@link #onProgressUpdate} will note be called if the task has been |
| * canceled. |
| * |
| * @param values The progress values to update the UI with. |
| * |
| * @see #onProgressUpdate |
| * @see #doInBackground |
| */ |
| protected final void publishProgress(Progress... values) { |
| if (!isCancelled()) { |
| sHandler.obtainMessage(MESSAGE_POST_PROGRESS, |
| new AsyncTaskResult<Progress>(this, values)).sendToTarget(); |
| } |
| } |
| |
| private void finish(Result result) { |
| if (isCancelled()) { |
| onCancelled(result); |
| } else { |
| onPostExecute(result); |
| } |
| mStatus = Status.FINISHED; |
| } |
| |
| private static class InternalHandler extends Handler { |
| @SuppressWarnings({"unchecked", "RawUseOfParameterizedType"}) |
| @Override |
| public void handleMessage(Message msg) { |
| AsyncTaskResult result = (AsyncTaskResult) msg.obj; |
| switch (msg.what) { |
| case MESSAGE_POST_RESULT: |
| // There is only one result |
| result.mTask.finish(result.mData[0]); |
| break; |
| case MESSAGE_POST_PROGRESS: |
| result.mTask.onProgressUpdate(result.mData); |
| break; |
| } |
| } |
| } |
| |
| private static abstract class WorkerRunnable<Params, Result> implements Callable<Result> { |
| Params[] mParams; |
| } |
| |
| @SuppressWarnings({"RawUseOfParameterizedType"}) |
| private static class AsyncTaskResult<Data> { |
| final AsyncTask mTask; |
| final Data[] mData; |
| |
| AsyncTaskResult(AsyncTask task, Data... data) { |
| mTask = task; |
| mData = data; |
| } |
| } |
| } |