1/*
2 * Copyright (C) 2007 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
17package android.database;
18
19/**
20 * A specialization of {@link Observable} for {@link DataSetObserver}
21 * that provides methods for sending notifications to a list of
22 * {@link DataSetObserver} objects.
23 */
24public class DataSetObservable extends Observable<DataSetObserver> {
25    /**
26     * Invokes {@link DataSetObserver#onChanged} on each observer.
27     * Called when the contents of the data set have changed.  The recipient
28     * will obtain the new contents the next time it queries the data set.
29     */
30    public void notifyChanged() {
31        synchronized(mObservers) {
32            // since onChanged() is implemented by the app, it could do anything, including
33            // removing itself from {@link mObservers} - and that could cause problems if
34            // an iterator is used on the ArrayList {@link mObservers}.
35            // to avoid such problems, just march thru the list in the reverse order.
36            for (int i = mObservers.size() - 1; i >= 0; i--) {
37                mObservers.get(i).onChanged();
38            }
39        }
40    }
41
42    /**
43     * Invokes {@link DataSetObserver#onInvalidated} on each observer.
44     * Called when the data set is no longer valid and cannot be queried again,
45     * such as when the data set has been closed.
46     */
47    public void notifyInvalidated() {
48        synchronized (mObservers) {
49            for (int i = mObservers.size() - 1; i >= 0; i--) {
50                mObservers.get(i).onInvalidated();
51            }
52        }
53    }
54}
55