1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
/*
* 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.os;
import android.os.ICancellationSignal;
import dalvik.annotation.compat.UnsupportedAppUsage;
/**
* Provides the ability to cancel an operation in progress.
*/
public final class CancellationSignal {
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
private boolean mIsCanceled;
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
private OnCancelListener mOnCancelListener;
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
private ICancellationSignal mRemote;
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
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 ICancellationSignal remote;
synchronized (this) {
if (mIsCanceled) {
return;
}
mIsCanceled = true;
mCancelInProgress = true;
listener = mOnCancelListener;
remote = mRemote;
}
try {
if (listener != null) {
listener.onCancel();
}
if (remote != null) {
try {
remote.cancel();
} catch (RemoteException ex) {
}
}
} 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();
}
/**
* Sets the remote transport.
*
* If {@link CancellationSignal#cancel} has already been called, then the provided
* remote transport is canceled immediately.
*
* This method is guaranteed that the remote transport will not be called after it
* has been removed.
*
* @param remote The remote transport, or null to remove.
*
* @hide
*/
public void setRemote(ICancellationSignal remote) {
synchronized (this) {
waitForCancelFinishedLocked();
if (mRemote == remote) {
return;
}
mRemote = remote;
if (!mIsCanceled || remote == null) {
return;
}
}
try {
remote.cancel();
} catch (RemoteException ex) {
}
}
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
private void waitForCancelFinishedLocked() {
while (mCancelInProgress) {
try {
wait();
} catch (InterruptedException ex) {
}
}
}
/**
* Creates a transport that can be returned back to the caller of
* a Binder function and subsequently used to dispatch a cancellation signal.
*
* @return The new cancellation signal transport.
*
* @hide
*/
public static ICancellationSignal createTransport() {
return new Transport();
}
/**
* Given a locally created transport, returns its associated cancellation signal.
*
* @param transport The locally created transport, or null if none.
* @return The associated cancellation signal, or null if none.
*
* @hide
*/
public static CancellationSignal fromTransport(ICancellationSignal transport) {
if (transport instanceof Transport) {
return ((Transport)transport).mCancellationSignal;
}
return null;
}
/**
* Listens for cancellation.
*/
public interface OnCancelListener {
/**
* Called when {@link CancellationSignal#cancel} is invoked.
*/
void onCancel();
}
private static final class Transport extends ICancellationSignal.Stub {
final CancellationSignal mCancellationSignal = new CancellationSignal();
@Override
public void cancel() throws RemoteException {
mCancellationSignal.cancel();
}
}
}
|
