/**
* Load an image specified by the data parameter into an ImageView (override {@link
* ImageWorker#processBitmap(Object)} to define the processing logic). A memory and disk cache
* will be used if an {@link ImageCache} has been set using {@link ImageWorker#addImageCache}. If
* the image is found in the memory cache, it is set immediately, otherwise an {@link AsyncTask}
* will be created to asynchronously load the bitmap.
*
* @param data The URL of the image to download.
* @param imageView The ImageView to bind the downloaded image to.
*/
public void loadImage(Object data, ImageView imageView, Bitmap loadingBitmap) {
if (data == null) {
return;
}
Bitmap bitmap = null;
if (mImageCache != null) {
bitmap = mImageCache.getBitmapFromMemCache(String.valueOf(data));
}
if (bitmap != null) {
// Bitmap found in memory cache
imageView.setImageBitmap(bitmap);
} else if (cancelPotentialWork(data, imageView)) {
final BitmapWorkerTask task = new BitmapWorkerTask(imageView);
final AsyncDrawable asyncDrawable = new AsyncDrawable(mResources, loadingBitmap, task);
imageView.setImageDrawable(asyncDrawable);
if (UIUtils.hasHoneycomb()) {
// On HC+ we execute on a dual thread executor. There really isn't much extra
// benefit to having a really large pool of threads. Having more than one will
// likely benefit network bottlenecks though.
task.executeOnExecutor(DUAL_THREAD_EXECUTOR, data);
} else {
// Otherwise pre-HC the default is a thread pool executor (not ideal, serial
// execution or a smaller number of threads would be better).
task.execute(data);
}
}
}
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public static Set<String> getStringSet(
final SharedPreferences pref, final String key, final Set<String> defaultValue) {
if (UIUtils.hasHoneycomb()) {
return pref.getStringSet(key, defaultValue);
} else {
final Set<String> set = new HashSet<String>();
int i = 0;
Set<String> keySet = pref.getAll().keySet();
while (keySet.contains(key + i)) {
set.add(pref.getString(key + i, ""));
i++;
}
if (set.isEmpty()) {
return defaultValue;
} else {
return set;
}
}
}
/**
* ************************************* Copied from JB release framework:
* https://android.googlesource.com/platform/frameworks/base/+/jb-release/core/java/android/os/AsyncTask.java
*
* <p>so that threading behavior on all OS versions is the same and we can tweak behavior by using
* executeOnExecutor() if needed.
*
* <p>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>
*
* <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
* android.os.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 java.util.concurrent.Executor},
* {@link java.util.concurrent.ThreadPoolExecutor} and {@link java.util.concurrent.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. </div>
*
* <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:
*
* <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; }
* <p/>
* protected void onProgressUpdate(Integer... progress) { setProgressPercent(progress[0]); }
* <p/>
* protected void onPostExecute(Long result) { showDialog("Downloaded " + result + " bytes"); } }
* </pre>
*
* <p>
*
* <p>Once created, a task is executed very simply:
*
* <pre class="prettyprint"> new
* DownloadFilesTask().execute(url1, url2, url3); </pre>
*
* <p>
*
* <h2>AsyncTask's generic types</h2>
*
* <p>The three types used by an asynchronous task are the following:
*
* <ol>
* <li><code>Params</code>, the type of the parameters sent to the task upon execution.
* <li><code>Progress</code>, the type of the progress units published during the background
* computation.
* <li><code>Result</code>, the type of the result of the background computation.
* </ol>
*
* <p>Not all types are always used by an asynchronous task. To mark a type as unused, simply use
* the type {@link Void}:
*
* <pre> private class MyTask extends
* AsyncTask<Void, Void, Void> { ... } </pre>
*
* <p>
*
* <h2>The 4 steps</h2>
*
* <p>When an asynchronous task is executed, the task goes through 4 steps:
*
* <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>{@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>{@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>{@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.
* </ol>
*
* <p>
*
* <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:
*
* <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>The task instance must be created on the UI thread.
* <li>{@link #execute} must be invoked on the UI thread.
* <li>Do not call {@link #onPreExecute()}, {@link #onPostExecute}, {@link #doInBackground},
* {@link #onProgressUpdate} manually.
* <li>The task can be executed only once (an exception will be thrown if a second execution is
* attempted.)
* </ul>
*
* <p>
*
* <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.
*
* <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>
*
* <p>
*
* <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>If you truly want parallel execution, you can invoke {@link
* #executeOnExecutor(java.util.concurrent.Executor, Object[])} with {@link #THREAD_POOL_EXECUTOR}.
*/
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 java.util.concurrent.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 java.util.concurrent.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 =
UIUtils.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 uk.org.ngo.squeezer.util.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.
*
* <p>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
*/
@SuppressWarnings("EmptyMethod")
protected void onPreExecute() {}
/**
* 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.
*
* @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) {}
/**
* 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>.
*
* @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();
}
/**
* 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.
*
* @see #onCancelled(Object)
* @see #cancel(boolean)
* @see #isCancelled()
*/
@SuppressWarnings("EmptyMethod")
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();
}
/**
* 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.
*
* @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 java.util.concurrent.CancellationException If the computation was cancelled.
* @throws java.util.concurrent.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 java.util.concurrent.CancellationException If the computation was cancelled.
* @throws java.util.concurrent.ExecutionException If the computation threw an exception.
* @throws InterruptedException If the current thread was interrupted while waiting.
* @throws java.util.concurrent.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>
*
* <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>
*
* <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
* uk.org.ngo.squeezer.util.AsyncTask.Status#RUNNING} or {@link
* uk.org.ngo.squeezer.util.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>
*
* <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 java.util.concurrent.Executor} for custom behavior.
*
* <p>
*
* <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>
*
* <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
* uk.org.ngo.squeezer.util.AsyncTask.Status#RUNNING} or {@link
* uk.org.ngo.squeezer.util.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.
*
* <p>{@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 abstract static 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;
}
}
}
