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/* * Copyright (C) 2008 The Android Open Source Project *//from www . ja v a 2 s .co m * 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 ginger.connexus.util; import android.annotation.TargetApi; import android.os.Handler; import android.os.Message; import android.os.Process; 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.Executors; 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; /** * ************************************* Copied from JB release framework: * https: * //android.googlesource.com/platform/frameworks/base/+/jb-release/core/java * /android/os/AsyncTask.java * * so that threading behavior on all OS versions is the same and we can tweak * behavior by using executeOnExecutor() if needed. * * There are 3 changes in this copy of AsyncTask: -pre-HC a single thread * executor is used for serial operation (Executors.newSingleThreadExecutor) and * is the default -the default THREAD_POOL_EXECUTOR was changed to use * DiscardOldestPolicy -a new fixed thread pool called DUAL_THREAD_EXECUTOR was * added ************************************* * * <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 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 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, new ThreadPoolExecutor.DiscardOldestPolicy()); /** * 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 = Utils.hasHoneycomb() ? new SerialExecutor() : Executors .newSingleThreadExecutor(sThreadFactory); public static final Executor DUAL_THREAD_EXECUTOR = Executors.newFixedThreadPool(2, sThreadFactory); 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(); @TargetApi(11) 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({}) 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({}) 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({}) 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[]) */ @SuppressWarnings("incomplete-switch") 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", "rawtypes" }) @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("rawtypes") private static class AsyncTaskResult<Data> { final AsyncTask mTask; final Data[] mData; AsyncTaskResult(AsyncTask task, Data... data) { mTask = task; mData = data; } } }