FilteredUpdatable.java revision 4961ad31d9a877e3a68566fb5d4b33b7f79ce44e 
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
19import javax.annotation.Nonnull;
20
21/**
22 * Wraps an {@link com.android.camera.async.Updatable} by filtering out
23 * duplicate updates.
24 */
25public class FilteredUpdatable<T> implements Updatable<T> {
26    private final Updatable<T> mUpdatable;
27    private final Object mLock;
28    private boolean mValueSet;
29    private T mLatestValue;
30
31    public FilteredUpdatable(Updatable<T> updatable) {
32        mUpdatable = updatable;
33        mLock = new Object();
34        mValueSet = false;
35        mLatestValue = null;
36    }
37
38    @Override
39    public void update(@Nonnull T t) {
40        synchronized (mLock) {
41            if (!mValueSet) {
42                setNewValue(t);
43            } else {
44                if (t == null && mLatestValue != null) {
45                    setNewValue(t);
46                } else if (t != null) {
47                    if (!t.equals(mLatestValue)) {
48                        setNewValue(t);
49                    }
50                }
51            }
52        }
53    }
54
55    private void setNewValue(T value) {
56        synchronized (mLock) {
57            mUpdatable.update(value);
58            mLatestValue = value;
59            mValueSet = true;
60        }
61    }
62}
63