1 /*
2  * Copyright (C) 2019 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.view.accessibility;
18 
19 import android.util.SparseArray;
20 
21 import java.lang.ref.Reference;
22 import java.lang.ref.ReferenceQueue;
23 import java.lang.ref.WeakReference;
24 
25 
26 final class WeakSparseArray<E> {
27 
28     private final ReferenceQueue<E> mRefQueue = new ReferenceQueue<>();
29     private final SparseArray<WeakReferenceWithId<E>> mSparseArray = new SparseArray<>();
30 
append(int key, E value)31     public void append(int key, E value) {
32         removeUnreachableValues();
33         mSparseArray.append(key, new WeakReferenceWithId(value, mRefQueue, key));
34     }
35 
remove(int key)36     public void remove(int key) {
37         removeUnreachableValues();
38         mSparseArray.remove(key);
39     }
40 
get(int key)41     public E get(int key) {
42         removeUnreachableValues();
43         WeakReferenceWithId<E> ref = mSparseArray.get(key);
44         return ref != null ? ref.get() : null;
45     }
46 
removeUnreachableValues()47     private void removeUnreachableValues() {
48         for (Reference ref = mRefQueue.poll(); ref != null; ref = mRefQueue.poll()) {
49             mSparseArray.remove(((WeakReferenceWithId) ref).mId);
50         }
51     }
52 
53     private static class WeakReferenceWithId<E> extends WeakReference<E> {
54 
55         final int mId;
56 
WeakReferenceWithId(E referent, ReferenceQueue<? super E> q, int id)57         WeakReferenceWithId(E referent, ReferenceQueue<? super E> q, int id) {
58             super(referent, q);
59             mId = id;
60         }
61     }
62 }
63 
64