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Diffstat (limited to 'platform/android/src/com/artifex/mupdfdemo/AsyncTask.java')
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diff --git a/platform/android/src/com/artifex/mupdfdemo/AsyncTask.java b/platform/android/src/com/artifex/mupdfdemo/AsyncTask.java new file mode 100644 index 00000000..b370794c --- /dev/null +++ b/platform/android/src/com/artifex/mupdfdemo/AsyncTask.java @@ -0,0 +1,670 @@ +/* + * 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 com.artifex.mupdfdemo; + +import java.util.concurrent.BlockingQueue; +import java.util.concurrent.Callable; +import java.util.concurrent.CancellationException; +import java.util.concurrent.ExecutionException; +import java.util.concurrent.Executor; +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; + +import android.os.Process; +import android.os.Handler; +import android.os.Message; + +/** + * <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>AsyncTask is designed to be a helper class around {@link Thread} and {@link Handler} + * and does not constitute a generic threading framework. AsyncTasks should ideally be + * used for short operations (a few seconds at the most.) If you need to keep threads + * running for long periods of time, it is highly recommended you use the various APIs + * provided by the <code>java.util.concurrent</code> pacakge such as {@link Executor}, + * {@link ThreadPoolExecutor} and {@link FutureTask}.</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)); + * // Escape early if cancel() is called + * if (isCancelled()) break; + * } + * 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 before 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 AsyncTask class must be loaded on the UI thread. This is done + * automatically as of {@link android.os.Build.VERSION_CODES#JELLY_BEAN}.</li> + * <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> + * + * <h2>Order of execution</h2> + * <p>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. Starting with + * {@link android.os.Build.VERSION_CODES#HONEYCOMB}, tasks are executed on a single + * thread to avoid common application errors caused by parallel execution.</p> + * <p>If you truly want parallel execution, you can invoke + * {@link #executeOnExecutor(java.util.concurrent.Executor, Object[])} with + * {@link #THREAD_POOL_EXECUTOR}.</p> + */ +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); + } + } + }; + } + + 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. Starting + * {@link android.os.Build.VERSION_CODES#HONEYCOMB}, tasks are back to being + * executed on 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}. + * + * @see #executeOnExecutor(java.util.concurrent.Executor, Object[]) + * @see #execute(Runnable) + */ + 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}. + * + * @see #execute(Object[]) + */ + 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. See {@link #execute(Object[])} for more + * information on the order of execution. + * + * @see #execute(Object[]) + * @see #executeOnExecutor(java.util.concurrent.Executor, 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; + } + } +} |