1/*
2 * Copyright (C) 2013 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.server;
18
19import android.os.Handler;
20import android.os.Trace;
21
22/**
23 * Shared singleton thread for showing UI.  This is a foreground thread, and in
24 * additional should not have operations that can take more than a few ms scheduled
25 * on it to avoid UI jank.
26 */
27public final class UiThread extends ServiceThread {
28    private static UiThread sInstance;
29    private static Handler sHandler;
30
31    private UiThread() {
32        super("android.ui", android.os.Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
33    }
34
35    private static void ensureThreadLocked() {
36        if (sInstance == null) {
37            sInstance = new UiThread();
38            sInstance.start();
39            sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER);
40            sHandler = new Handler(sInstance.getLooper());
41        }
42    }
43
44    public static UiThread get() {
45        synchronized (UiThread.class) {
46            ensureThreadLocked();
47            return sInstance;
48        }
49    }
50
51    public static Handler getHandler() {
52        synchronized (UiThread.class) {
53            ensureThreadLocked();
54            return sHandler;
55        }
56    }
57}
58