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Merge "Tighten up AsyncTask's semantics and behavior. Bug #3109366 Bug #3109382" into honeycomb

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This commit is contained in:
Romain Guy
2011-01-09 14:01:42 -08:00
committed by Android (Google) Code Review
parent ccf9d10bd4 e95003e4a1
commit fcd3e8e6fa
2 changed files with 48 additions and 38 deletions
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83
core/java/android/os/AsyncTask.java
View File

@@ -111,6 +111,15 @@ import java.util.concurrent.atomic.AtomicInteger;
* 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()}, 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
@@ -157,7 +166,6 @@ public abstract class AsyncTask<Params, Progress, Result> {
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();
@@ -197,47 +205,33 @@ public abstract class AsyncTask<Params, Progress, Result> {
mWorker = new WorkerRunnable<Params, Result>() {
public Result call() throws Exception {
Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
return doInBackground(mParams);
Result result = doInBackground(mParams);
Message message = sHandler.obtainMessage(MESSAGE_POST_RESULT,
new AsyncTaskResult<Result>(AsyncTask.this, result));
message.sendToTarget();
return result;
}
};
mFuture = new FutureTask<Result>(mWorker) {
@Override
protected void set(Result v) {
super.set(v);
if (isCancelled()) {
Message message = sHandler.obtainMessage(MESSAGE_POST_CANCEL,
new AsyncTaskResult<Result>(AsyncTask.this, (Result[]) null));
message.sendToTarget();
}
}
@Override
protected void done() {
Message message;
Result result = null;
try {
result = get();
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;
// Taken care of in the WorkerRunnable
} 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();
}
};
}
@@ -279,14 +273,16 @@ public abstract class AsyncTask<Params, Progress, Result> {
}
/**
* 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 occurred.
* <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()
*/
@SuppressWarnings({"UnusedDeclaration"})
protected void onPostExecute(Result result) {
@@ -306,7 +302,8 @@ public abstract class AsyncTask<Params, Progress, Result> {
}
/**
* Runs on the UI thread after {@link #cancel(boolean)} is invoked.
* Runs on the UI thread after {@link #cancel(boolean)} is invoked and
* {@link #doInBackground(Object[])} has finished.
*
* @see #cancel(boolean)
* @see #isCancelled()
@@ -316,7 +313,9 @@ public abstract class AsyncTask<Params, Progress, Result> {
/**
* Returns <tt>true</tt> if this task was cancelled before it completed
* normally.
* 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
*
@@ -327,14 +326,22 @@ public abstract class AsyncTask<Params, Progress, Result> {
}
/**
* Attempts to cancel execution of this task. This attempt will
* <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,
* 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.
* an attempt to stop the task.</p>
*
* <p>Calling this method will result in {@link #onCancelled()} 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
@@ -444,8 +451,11 @@ public abstract class AsyncTask<Params, Progress, Result> {
}
private void finish(Result result) {
if (isCancelled()) result = null;
onPostExecute(result);
if (isCancelled()) {
onCancelled();
} else {
onPostExecute(result);
}
mStatus = Status.FINISHED;
}
@@ -462,9 +472,6 @@ public abstract class AsyncTask<Params, Progress, Result> {
case MESSAGE_POST_PROGRESS:
result.mTask.onProgressUpdate(result.mData);
break;
case MESSAGE_POST_CANCEL:
result.mTask.onCancelled();
break;
}
}
}

3
core/java/android/view/ViewGroup.java
View File

@@ -130,12 +130,15 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
private MotionEvent.PointerCoords[] mTmpPointerCoords;
// For debugging only. You can see these in hierarchyviewer.
@SuppressWarnings({"FieldCanBeLocal", "UnusedDeclaration"})
@ViewDebug.ExportedProperty(category = "events")
private long mLastTouchDownTime;
@ViewDebug.ExportedProperty(category = "events")
private int mLastTouchDownIndex = -1;
@SuppressWarnings({"FieldCanBeLocal", "UnusedDeclaration"})
@ViewDebug.ExportedProperty(category = "events")
private float mLastTouchDownX;
@SuppressWarnings({"FieldCanBeLocal", "UnusedDeclaration"})
@ViewDebug.ExportedProperty(category = "events")
private float mLastTouchDownY;