| /* |
| * Copyright (C) 2012 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.support.v4.os; |
| |
| import android.os.Build; |
| |
| /** |
| * Static library support version of the framework's {@link android.os.CancellationSignal}. |
| * Used to write apps that run on platforms prior to Android 4.1. See the framework SDK |
| * documentation for a class overview. |
| */ |
| public final class CancellationSignal { |
| private boolean mIsCanceled; |
| private OnCancelListener mOnCancelListener; |
| private Object mCancellationSignalObj; |
| private boolean mCancelInProgress; |
| |
| /** |
| * Creates a cancellation signal, initially not canceled. |
| */ |
| public CancellationSignal() { |
| } |
| |
| /** |
| * Returns true if the operation has been canceled. |
| * |
| * @return True if the operation has been canceled. |
| */ |
| public boolean isCanceled() { |
| synchronized (this) { |
| return mIsCanceled; |
| } |
| } |
| |
| /** |
| * Throws {@link OperationCanceledException} if the operation has been canceled. |
| * |
| * @throws OperationCanceledException if the operation has been canceled. |
| */ |
| public void throwIfCanceled() { |
| if (isCanceled()) { |
| throw new OperationCanceledException(); |
| } |
| } |
| |
| /** |
| * Cancels the operation and signals the cancellation listener. |
| * If the operation has not yet started, then it will be canceled as soon as it does. |
| */ |
| public void cancel() { |
| final OnCancelListener listener; |
| final Object obj; |
| synchronized (this) { |
| if (mIsCanceled) { |
| return; |
| } |
| mIsCanceled = true; |
| mCancelInProgress = true; |
| listener = mOnCancelListener; |
| obj = mCancellationSignalObj; |
| } |
| |
| try { |
| if (listener != null) { |
| listener.onCancel(); |
| } |
| if (obj != null) { |
| CancellationSignalCompatJellybean.cancel(obj); |
| } |
| } finally { |
| synchronized (this) { |
| mCancelInProgress = false; |
| notifyAll(); |
| } |
| } |
| } |
| |
| /** |
| * Sets the cancellation listener to be called when canceled. |
| * |
| * This method is intended to be used by the recipient of a cancellation signal |
| * such as a database or a content provider to handle cancellation requests |
| * while performing a long-running operation. This method is not intended to be |
| * used by applications themselves. |
| * |
| * If {@link CancellationSignal#cancel} has already been called, then the provided |
| * listener is invoked immediately. |
| * |
| * This method is guaranteed that the listener will not be called after it |
| * has been removed. |
| * |
| * @param listener The cancellation listener, or null to remove the current listener. |
| */ |
| public void setOnCancelListener(OnCancelListener listener) { |
| synchronized (this) { |
| waitForCancelFinishedLocked(); |
| |
| if (mOnCancelListener == listener) { |
| return; |
| } |
| mOnCancelListener = listener; |
| if (!mIsCanceled || listener == null) { |
| return; |
| } |
| } |
| listener.onCancel(); |
| } |
| |
| /** |
| * Gets the framework {@link android.os.CancellationSignal} associated with this object. |
| * <p> |
| * Framework support for cancellation signals was added in |
| * {@link android.os.Build.VERSION_CODES#JELLY_BEAN} so this method will always |
| * return null on older versions of the platform. |
| * </p> |
| * |
| * @return A framework cancellation signal object, or null on platform versions |
| * prior to Jellybean. |
| */ |
| public Object getCancellationSignalObject() { |
| if (Build.VERSION.SDK_INT < 16) { |
| return null; |
| } |
| synchronized (this) { |
| if (mCancellationSignalObj == null) { |
| mCancellationSignalObj = CancellationSignalCompatJellybean.create(); |
| if (mIsCanceled) { |
| CancellationSignalCompatJellybean.cancel(mCancellationSignalObj); |
| } |
| } |
| return mCancellationSignalObj; |
| } |
| } |
| |
| private void waitForCancelFinishedLocked() { |
| while (mCancelInProgress) { |
| try { |
| wait(); |
| } catch (InterruptedException ex) { |
| } |
| } |
| } |
| |
| /** |
| * Listens for cancellation. |
| */ |
| public interface OnCancelListener { |
| /** |
| * Called when {@link CancellationSignal#cancel} is invoked. |
| */ |
| void onCancel(); |
| } |
| } |