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diff --git a/core/java/android/os/AsyncTask.java b/core/java/android/os/AsyncTask.java
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+/*
+ * 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.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.Callable;
+import java.util.concurrent.FutureTask;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.CancellationException;
+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>begin</code>, <code>doInBackground</code>,
+ * <code>processProgress<code> and <code>end</code>.</p>
+ *
+ * <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&lt;URL, Integer, Long&gt; {
+ *     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 am 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>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>
+ */
+public abstract class AsyncTask<Params, Progress, Result> {
+    private static final String LOG_TAG = "AsyncTask";
+
+    private static final int CORE_POOL_SIZE = 1;
+    private static final int MAXIMUM_POOL_SIZE = 10;
+    private static final int KEEP_ALIVE = 10;
+
+    private static final BlockingQueue<Runnable> sWorkQueue =
+            new LinkedBlockingQueue<Runnable>(MAXIMUM_POOL_SIZE);
+
+    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 ThreadPoolExecutor sExecutor = new ThreadPoolExecutor(CORE_POOL_SIZE,
+            MAXIMUM_POOL_SIZE, KEEP_ALIVE, TimeUnit.SECONDS, sWorkQueue, sThreadFactory);
+
+    private static final int MESSAGE_POST_RESULT = 0x1;
+    private static final int MESSAGE_POST_PROGRESS = 0x2;
+    private static final int MESSAGE_POST_CANCEL = 0x3;
+
+    private static final InternalHandler sHandler = new InternalHandler();
+
+    private final WorkerRunnable<Params, Result> mWorker;
+    private final FutureTask<Result> mFuture;
+
+    private volatile Status mStatus = Status.PENDING;
+
+    /**
+     * 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,
+    }
+
+    /**
+     * 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 {
+                Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
+                return doInBackground(mParams);
+            }
+        };
+
+        mFuture = new FutureTask<Result>(mWorker) {
+            @Override
+            protected void done() {
+                Message message;
+                Result result = null;
+
+                try {
+                    result = 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) {
+                    message = sHandler.obtainMessage(MESSAGE_POST_CANCEL,
+                            new AsyncTaskResult<Result>(AsyncTask.this, (Result[]) null));
+                    message.sendToTarget();
+                    return;
+                } catch (Throwable t) {
+                    throw new RuntimeException("An error occured while executing "
+                            + "doInBackground()", t);
+                }
+
+                message = sHandler.obtainMessage(MESSAGE_POST_RESULT,
+                        new AsyncTaskResult<Result>(AsyncTask.this, result));
+                message.sendToTarget();
+            }
+        };
+    }
+
+    /**
+     * 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() {
+    }
+
+    /**
+     * Runs on the UI thread after {@link #doInBackground}. The
+     * specified result is the value returned by {@link #doInBackground}
+     * or null if the task was cancelled or an exception occured.
+     *
+     * @param result The result of the operation computed by {@link #doInBackground}.
+     *
+     * @see #onPreExecute
+     * @see #doInBackground
+     */
+    @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) {
+    }
+
+    /**
+     * Runs on the UI thread after {@link #cancel(boolean)} is invoked.
+     *
+     * @see #cancel(boolean)
+     * @see #isCancelled()
+     */
+    protected void onCancelled() {
+    }
+
+    /**
+     * Returns <tt>true</tt> if this task was cancelled before it completed
+     * normally.
+     *
+     * @return <tt>true</tt> if task was cancelled before it completed
+     *
+     * @see #cancel(boolean)
+     */
+    public final boolean isCancelled() {
+        return mFuture.isCancelled();
+    }
+
+    /**
+     * 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.
+     *
+     * @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()
+     */
+    public final boolean cancel(boolean mayInterruptIfRunning) {
+        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.
+     *
+     * 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) {
+        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;
+        sExecutor.execute(mFuture);
+
+        return this;
+    }
+
+    /**
+     * 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.
+     *
+     * @param values The progress values to update the UI with.
+     *
+     * @see #onProgressUpdate
+     * @see #doInBackground
+     */
+    protected final void publishProgress(Progress... values) {
+        sHandler.obtainMessage(MESSAGE_POST_PROGRESS,
+                new AsyncTaskResult<Progress>(this, values)).sendToTarget();
+    }
+
+    private void finish(Result result) {
+        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;
+                case MESSAGE_POST_CANCEL:
+                    result.mTask.onCancelled();
+                    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;
+        }
+    }
+}