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.Looper;
21import android.os.Process;
22import android.os.Trace;
23
24/**
25 * Shared singleton thread for showing UI.  This is a foreground thread, and in
26 * additional should not have operations that can take more than a few ms scheduled
27 * on it to avoid UI jank.
28 */
29public final class UiThread extends ServiceThread {
30    private static final long SLOW_DISPATCH_THRESHOLD_MS = 100;
31    private static final long SLOW_DELIVERY_THRESHOLD_MS = 200;
32    private static UiThread sInstance;
33    private static Handler sHandler;
34
35    private UiThread() {
36        super("android.ui", Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
37    }
38
39    @Override
40    public void run() {
41        // Make sure UiThread is in the fg stune boost group
42        Process.setThreadGroup(Process.myTid(), Process.THREAD_GROUP_TOP_APP);
43        super.run();
44    }
45
46    private static void ensureThreadLocked() {
47        if (sInstance == null) {
48            sInstance = new UiThread();
49            sInstance.start();
50            final Looper looper = sInstance.getLooper();
51            looper.setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);
52            looper.setSlowLogThresholdMs(
53                    SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);
54            sHandler = new Handler(sInstance.getLooper());
55        }
56    }
57
58    public static UiThread get() {
59        synchronized (UiThread.class) {
60            ensureThreadLocked();
61            return sInstance;
62        }
63    }
64
65    public static Handler getHandler() {
66        synchronized (UiThread.class) {
67            ensureThreadLocked();
68            return sHandler;
69        }
70    }
71}
72