| /* |
| * Copyright (C) 2010 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.content; |
| |
| import android.compat.annotation.UnsupportedAppUsage; |
| import android.os.AsyncTask; |
| import android.os.Handler; |
| import android.os.OperationCanceledException; |
| import android.os.SystemClock; |
| import android.util.Log; |
| import android.util.TimeUtils; |
| |
| import java.io.FileDescriptor; |
| import java.io.PrintWriter; |
| import java.util.concurrent.CountDownLatch; |
| import java.util.concurrent.Executor; |
| |
| /** |
| * Abstract Loader that provides an {@link AsyncTask} to do the work. See |
| * {@link Loader} and {@link android.app.LoaderManager} for more details. |
| * |
| * <p>Here is an example implementation of an AsyncTaskLoader subclass that |
| * loads the currently installed applications from the package manager. This |
| * implementation takes care of retrieving the application labels and sorting |
| * its result set from them, monitoring for changes to the installed |
| * applications, and rebuilding the list when a change in configuration requires |
| * this (such as a locale change). |
| * |
| * {@sample development/samples/ApiDemos/src/com/example/android/apis/app/LoaderCustom.java |
| * loader} |
| * |
| * <p>An example implementation of a fragment that uses the above loader to show |
| * the currently installed applications in a list is below. |
| * |
| * {@sample development/samples/ApiDemos/src/com/example/android/apis/app/LoaderCustom.java |
| * fragment} |
| * |
| * @param <D> the data type to be loaded. |
| * |
| * @deprecated Use the <a href="{@docRoot}tools/extras/support-library.html">Support Library</a> |
| * {@link androidx.loader.content.AsyncTaskLoader} |
| */ |
| @Deprecated |
| public abstract class AsyncTaskLoader<D> extends Loader<D> { |
| static final String TAG = "AsyncTaskLoader"; |
| static final boolean DEBUG = false; |
| |
| final class LoadTask extends AsyncTask<Void, Void, D> implements Runnable { |
| private final CountDownLatch mDone = new CountDownLatch(1); |
| |
| // Set to true to indicate that the task has been posted to a handler for |
| // execution at a later time. Used to throttle updates. |
| boolean waiting; |
| |
| /* Runs on a worker thread */ |
| @Override |
| protected D doInBackground(Void... params) { |
| if (DEBUG) Log.v(TAG, this + " >>> doInBackground"); |
| try { |
| D data = AsyncTaskLoader.this.onLoadInBackground(); |
| if (DEBUG) Log.v(TAG, this + " <<< doInBackground"); |
| return data; |
| } catch (OperationCanceledException ex) { |
| if (!isCancelled()) { |
| // onLoadInBackground threw a canceled exception spuriously. |
| // This is problematic because it means that the LoaderManager did not |
| // cancel the Loader itself and still expects to receive a result. |
| // Additionally, the Loader's own state will not have been updated to |
| // reflect the fact that the task was being canceled. |
| // So we treat this case as an unhandled exception. |
| throw ex; |
| } |
| if (DEBUG) Log.v(TAG, this + " <<< doInBackground (was canceled)", ex); |
| return null; |
| } |
| } |
| |
| /* Runs on the UI thread */ |
| @Override |
| protected void onPostExecute(D data) { |
| if (DEBUG) Log.v(TAG, this + " onPostExecute"); |
| try { |
| AsyncTaskLoader.this.dispatchOnLoadComplete(this, data); |
| } finally { |
| mDone.countDown(); |
| } |
| } |
| |
| /* Runs on the UI thread */ |
| @Override |
| protected void onCancelled(D data) { |
| if (DEBUG) Log.v(TAG, this + " onCancelled"); |
| try { |
| AsyncTaskLoader.this.dispatchOnCancelled(this, data); |
| } finally { |
| mDone.countDown(); |
| } |
| } |
| |
| /* Runs on the UI thread, when the waiting task is posted to a handler. |
| * This method is only executed when task execution was deferred (waiting was true). */ |
| @Override |
| public void run() { |
| waiting = false; |
| AsyncTaskLoader.this.executePendingTask(); |
| } |
| |
| /* Used for testing purposes to wait for the task to complete. */ |
| public void waitForLoader() { |
| try { |
| mDone.await(); |
| } catch (InterruptedException e) { |
| // Ignore |
| } |
| } |
| } |
| |
| @UnsupportedAppUsage |
| private final Executor mExecutor; |
| |
| volatile LoadTask mTask; |
| volatile LoadTask mCancellingTask; |
| |
| long mUpdateThrottle; |
| long mLastLoadCompleteTime = -10000; |
| Handler mHandler; |
| |
| public AsyncTaskLoader(Context context) { |
| this(context, AsyncTask.THREAD_POOL_EXECUTOR); |
| } |
| |
| /** {@hide} */ |
| public AsyncTaskLoader(Context context, Executor executor) { |
| super(context); |
| mExecutor = executor; |
| } |
| |
| /** |
| * Set amount to throttle updates by. This is the minimum time from |
| * when the last {@link #loadInBackground()} call has completed until |
| * a new load is scheduled. |
| * |
| * @param delayMS Amount of delay, in milliseconds. |
| */ |
| public void setUpdateThrottle(long delayMS) { |
| mUpdateThrottle = delayMS; |
| if (delayMS != 0) { |
| mHandler = new Handler(); |
| } |
| } |
| |
| @Override |
| protected void onForceLoad() { |
| super.onForceLoad(); |
| cancelLoad(); |
| mTask = new LoadTask(); |
| if (DEBUG) Log.v(TAG, "Preparing load: mTask=" + mTask); |
| executePendingTask(); |
| } |
| |
| @Override |
| protected boolean onCancelLoad() { |
| if (DEBUG) Log.v(TAG, "onCancelLoad: mTask=" + mTask); |
| if (mTask != null) { |
| if (!mStarted) { |
| mContentChanged = true; |
| } |
| if (mCancellingTask != null) { |
| // There was a pending task already waiting for a previous |
| // one being canceled; just drop it. |
| if (DEBUG) Log.v(TAG, |
| "cancelLoad: still waiting for cancelled task; dropping next"); |
| if (mTask.waiting) { |
| mTask.waiting = false; |
| mHandler.removeCallbacks(mTask); |
| } |
| mTask = null; |
| return false; |
| } else if (mTask.waiting) { |
| // There is a task, but it is waiting for the time it should |
| // execute. We can just toss it. |
| if (DEBUG) Log.v(TAG, "cancelLoad: task is waiting, dropping it"); |
| mTask.waiting = false; |
| mHandler.removeCallbacks(mTask); |
| mTask = null; |
| return false; |
| } else { |
| boolean cancelled = mTask.cancel(false); |
| if (DEBUG) Log.v(TAG, "cancelLoad: cancelled=" + cancelled); |
| if (cancelled) { |
| mCancellingTask = mTask; |
| cancelLoadInBackground(); |
| } |
| mTask = null; |
| return cancelled; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Called if the task was canceled before it was completed. Gives the class a chance |
| * to clean up post-cancellation and to properly dispose of the result. |
| * |
| * @param data The value that was returned by {@link #loadInBackground}, or null |
| * if the task threw {@link OperationCanceledException}. |
| */ |
| public void onCanceled(D data) { |
| } |
| |
| void executePendingTask() { |
| if (mCancellingTask == null && mTask != null) { |
| if (mTask.waiting) { |
| mTask.waiting = false; |
| mHandler.removeCallbacks(mTask); |
| } |
| if (mUpdateThrottle > 0) { |
| long now = SystemClock.uptimeMillis(); |
| if (now < (mLastLoadCompleteTime+mUpdateThrottle)) { |
| // Not yet time to do another load. |
| if (DEBUG) Log.v(TAG, "Waiting until " |
| + (mLastLoadCompleteTime+mUpdateThrottle) |
| + " to execute: " + mTask); |
| mTask.waiting = true; |
| mHandler.postAtTime(mTask, mLastLoadCompleteTime+mUpdateThrottle); |
| return; |
| } |
| } |
| if (DEBUG) Log.v(TAG, "Executing: " + mTask); |
| mTask.executeOnExecutor(mExecutor, (Void[]) null); |
| } |
| } |
| |
| void dispatchOnCancelled(LoadTask task, D data) { |
| onCanceled(data); |
| if (mCancellingTask == task) { |
| if (DEBUG) Log.v(TAG, "Cancelled task is now canceled!"); |
| rollbackContentChanged(); |
| mLastLoadCompleteTime = SystemClock.uptimeMillis(); |
| mCancellingTask = null; |
| if (DEBUG) Log.v(TAG, "Delivering cancellation"); |
| deliverCancellation(); |
| executePendingTask(); |
| } |
| } |
| |
| void dispatchOnLoadComplete(LoadTask task, D data) { |
| if (mTask != task) { |
| if (DEBUG) Log.v(TAG, "Load complete of old task, trying to cancel"); |
| dispatchOnCancelled(task, data); |
| } else { |
| if (isAbandoned()) { |
| // This cursor has been abandoned; just cancel the new data. |
| onCanceled(data); |
| } else { |
| commitContentChanged(); |
| mLastLoadCompleteTime = SystemClock.uptimeMillis(); |
| mTask = null; |
| if (DEBUG) Log.v(TAG, "Delivering result"); |
| deliverResult(data); |
| } |
| } |
| } |
| |
| /** |
| * Called on a worker thread to perform the actual load and to return |
| * the result of the load operation. |
| * |
| * Implementations should not deliver the result directly, but should return them |
| * from this method, which will eventually end up calling {@link #deliverResult} on |
| * the UI thread. If implementations need to process the results on the UI thread |
| * they may override {@link #deliverResult} and do so there. |
| * |
| * To support cancellation, this method should periodically check the value of |
| * {@link #isLoadInBackgroundCanceled} and terminate when it returns true. |
| * Subclasses may also override {@link #cancelLoadInBackground} to interrupt the load |
| * directly instead of polling {@link #isLoadInBackgroundCanceled}. |
| * |
| * When the load is canceled, this method may either return normally or throw |
| * {@link OperationCanceledException}. In either case, the {@link Loader} will |
| * call {@link #onCanceled} to perform post-cancellation cleanup and to dispose of the |
| * result object, if any. |
| * |
| * @return The result of the load operation. |
| * |
| * @throws OperationCanceledException if the load is canceled during execution. |
| * |
| * @see #isLoadInBackgroundCanceled |
| * @see #cancelLoadInBackground |
| * @see #onCanceled |
| */ |
| public abstract D loadInBackground(); |
| |
| /** |
| * Calls {@link #loadInBackground()}. |
| * |
| * This method is reserved for use by the loader framework. |
| * Subclasses should override {@link #loadInBackground} instead of this method. |
| * |
| * @return The result of the load operation. |
| * |
| * @throws OperationCanceledException if the load is canceled during execution. |
| * |
| * @see #loadInBackground |
| */ |
| protected D onLoadInBackground() { |
| return loadInBackground(); |
| } |
| |
| /** |
| * Called on the main thread to abort a load in progress. |
| * |
| * Override this method to abort the current invocation of {@link #loadInBackground} |
| * that is running in the background on a worker thread. |
| * |
| * This method should do nothing if {@link #loadInBackground} has not started |
| * running or if it has already finished. |
| * |
| * @see #loadInBackground |
| */ |
| public void cancelLoadInBackground() { |
| } |
| |
| /** |
| * Returns true if the current invocation of {@link #loadInBackground} is being canceled. |
| * |
| * @return True if the current invocation of {@link #loadInBackground} is being canceled. |
| * |
| * @see #loadInBackground |
| */ |
| public boolean isLoadInBackgroundCanceled() { |
| return mCancellingTask != null; |
| } |
| |
| /** |
| * Locks the current thread until the loader completes the current load |
| * operation. Returns immediately if there is no load operation running. |
| * Should not be called from the UI thread: calling it from the UI |
| * thread would cause a deadlock. |
| * <p> |
| * Use for testing only. <b>Never</b> call this from a UI thread. |
| * |
| * @hide |
| */ |
| @UnsupportedAppUsage |
| public void waitForLoader() { |
| LoadTask task = mTask; |
| if (task != null) { |
| task.waitForLoader(); |
| } |
| } |
| |
| @Override |
| public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) { |
| super.dump(prefix, fd, writer, args); |
| if (mTask != null) { |
| writer.print(prefix); writer.print("mTask="); writer.print(mTask); |
| writer.print(" waiting="); writer.println(mTask.waiting); |
| } |
| if (mCancellingTask != null) { |
| writer.print(prefix); writer.print("mCancellingTask="); writer.print(mCancellingTask); |
| writer.print(" waiting="); writer.println(mCancellingTask.waiting); |
| } |
| if (mUpdateThrottle != 0) { |
| writer.print(prefix); writer.print("mUpdateThrottle="); |
| TimeUtils.formatDuration(mUpdateThrottle, writer); |
| writer.print(" mLastLoadCompleteTime="); |
| TimeUtils.formatDuration(mLastLoadCompleteTime, |
| SystemClock.uptimeMillis(), writer); |
| writer.println(); |
| } |
| } |
| } |
