MainThread.java revision 386c5b885b99f67f9c0a7380f4be153f28333089 
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 android.os.Handler;
20import android.os.Looper;
21
22import com.google.common.annotations.VisibleForTesting;
23
24import javax.annotation.Nonnull;
25
26import static com.google.common.base.Preconditions.checkState;
27
28public class MainThread extends HandlerExecutor {
29    private MainThread(Handler handler) {
30        super(handler);
31    }
32
33    public static MainThread create() {
34        return new MainThread(new Handler(Looper.getMainLooper()));
35    }
36
37    /**
38     * Caches whether or not the current thread is the main thread.
39     */
40    private static final ThreadLocal<Boolean> sIsMainThread = new ThreadLocal<Boolean>() {
41        @Override
42        protected Boolean initialValue() {
43            return Looper.getMainLooper().getThread() == Thread.currentThread();
44        }
45    };
46
47    /**
48     * Asserts that the current thread is the main thread.
49     */
50    public static void checkMainThread() {
51        checkState(sIsMainThread.get(), "Not main thread.");
52    }
53
54    /**
55     * Returns a fake MainThreadExecutor which executes immediately.
56     */
57    @VisibleForTesting
58    public static MainThread createFakeForTesting() {
59        return new MainThread(null) {
60            @Override
61            public void execute(@Nonnull Runnable runnable) {
62                //
63                sIsMainThread.set(true);
64                try {
65                    runnable.run();
66                } finally {
67                    sIsMainThread.set(false);
68                }
69            }
70        };
71    }
72}
73