/
AsyncTask.java
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/
AsyncTask.java
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package nu.placebo.whatsup.android.os;
/*
* 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.
*/
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
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.AtomicInteger;
import android.os.Handler;
import android.os.Message;
import android.os.Process;
/**
*
* Android source code adapted to our needs. Removed varargs to avoid warnings
* when passing generic types into the execute(). Also removed the unneeded step
* (for us) of posting a progress update.
*
* The warnings in this file existed before we adapted it.
*
*/
public abstract class AsyncTask<Params, 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 = 10;
private static final BlockingQueue<Runnable> sWorkQueue = new LinkedBlockingQueue<Runnable>(
10);
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_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 = super.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({})
protected void onPostExecute(Result result) {
}
/**
* 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, 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;
}
private void finish(Result result) {
if (isCancelled())
result = null;
onPostExecute(result);
mStatus = Status.FINISHED;
}
private static class InternalHandler extends Handler {
@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_CANCEL:
result.mTask.onCancelled();
break;
}
}
}
private static abstract class WorkerRunnable<Params, Result> implements
Callable<Result> {
Params mParams;
}
private static class AsyncTaskResult<Data> {
final AsyncTask mTask;
final Data[] mData;
AsyncTaskResult(AsyncTask task, Data... data) {
mTask = task;
mData = data;
}
}
}