FilteredUpdatable.java revision 9c94ab32a69a1ad3642a0f1e38e68bcfd97d3511 
1/*
2 * Copyright (C) 2014 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 com.android.camera.async;
18
19/**
20 * Wraps an {@link com.android.camera.async.Updatable} by filtering out
21 * duplicate updates.
22 */
23public class FilteredUpdatable<T> implements Updatable<T> {
24    private final Updatable<T> mUpdatable;
25    private final Object mLock;
26    private boolean mValueSet;
27    private T mLatestValue;
28
29    public FilteredUpdatable(Updatable<T> updatable) {
30        mUpdatable = updatable;
31        mLock = new Object();
32        mValueSet = false;
33        mLatestValue = null;
34    }
35
36    @Override
37    public void update(T t) {
38        synchronized (mLock) {
39            if (!mValueSet) {
40                setNewValue(t);
41            } else {
42                if (t == null && mLatestValue != null) {
43                    setNewValue(t);
44                } else if (t != null) {
45                    if (!t.equals(mLatestValue)) {
46                        setNewValue(t);
47                    }
48                }
49            }
50        }
51    }
52
53    private void setNewValue(T value) {
54        synchronized (mLock) {
55            mUpdatable.update(value);
56            mLatestValue = value;
57            mValueSet = true;
58        }
59    }
60}
61