Brad Fitzpatrick | 333b8cb | 2010-08-26 12:04:57 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2010 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package android.app; |
| 18 | |
| 19 | import java.util.concurrent.ConcurrentLinkedQueue; |
| 20 | import java.util.concurrent.ExecutorService; |
| 21 | import java.util.concurrent.Executors; |
| 22 | |
| 23 | /** |
| 24 | * Internal utility class to keep track of process-global work that's |
| 25 | * outstanding and hasn't been finished yet. |
| 26 | * |
| 27 | * This was created for writing SharedPreference edits out |
| 28 | * asynchronously so we'd have a mechanism to wait for the writes in |
| 29 | * Activity.onPause and similar places, but we may use this mechanism |
| 30 | * for other things in the future. |
| 31 | * |
| 32 | * @hide |
| 33 | */ |
| 34 | public class QueuedWork { |
| 35 | |
| 36 | // The set of Runnables that will finish or wait on any async |
| 37 | // activities started by the application. |
| 38 | private static final ConcurrentLinkedQueue<Runnable> sPendingWorkFinishers = |
| 39 | new ConcurrentLinkedQueue<Runnable>(); |
| 40 | |
| 41 | private static ExecutorService sSingleThreadExecutor = null; // lazy, guarded by class |
| 42 | |
| 43 | /** |
| 44 | * Returns a single-thread Executor shared by the entire process, |
| 45 | * creating it if necessary. |
| 46 | */ |
| 47 | public static ExecutorService singleThreadExecutor() { |
| 48 | synchronized (QueuedWork.class) { |
| 49 | if (sSingleThreadExecutor == null) { |
| 50 | // TODO: can we give this single thread a thread name? |
| 51 | sSingleThreadExecutor = Executors.newSingleThreadExecutor(); |
| 52 | } |
| 53 | return sSingleThreadExecutor; |
| 54 | } |
| 55 | } |
| 56 | |
| 57 | /** |
| 58 | * Add a runnable to finish (or wait for) a deferred operation |
| 59 | * started in this context earlier. Typically finished by e.g. |
| 60 | * an Activity#onPause. Used by SharedPreferences$Editor#startCommit(). |
| 61 | * |
| 62 | * Note that this doesn't actually start it running. This is just |
| 63 | * a scratch set for callers doing async work to keep updated with |
| 64 | * what's in-flight. In the common case, caller code |
| 65 | * (e.g. SharedPreferences) will pretty quickly call remove() |
| 66 | * after an add(). The only time these Runnables are run is from |
| 67 | * waitToFinish(), below. |
| 68 | */ |
| 69 | public static void add(Runnable finisher) { |
| 70 | sPendingWorkFinishers.add(finisher); |
| 71 | } |
| 72 | |
| 73 | public static void remove(Runnable finisher) { |
| 74 | sPendingWorkFinishers.remove(finisher); |
| 75 | } |
| 76 | |
| 77 | /** |
| 78 | * Finishes or waits for async operations to complete. |
| 79 | * (e.g. SharedPreferences$Editor#startCommit writes) |
| 80 | * |
| 81 | * Is called from the Activity base class's onPause(), after |
| 82 | * BroadcastReceiver's onReceive, after Service command handling, |
| 83 | * etc. (so async work is never lost) |
| 84 | */ |
| 85 | public static void waitToFinish() { |
| 86 | Runnable toFinish; |
| 87 | while ((toFinish = sPendingWorkFinishers.poll()) != null) { |
| 88 | toFinish.run(); |
| 89 | } |
| 90 | } |
| 91 | } |