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 UiThread sInstance;
32    private static Handler sHandler;
33
34    private UiThread() {
35        super("android.ui", Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
36    }
37
38    @Override
39    public void run() {
40        // Make sure UiThread is in the fg stune boost group
41        Process.setThreadGroup(Process.myTid(), Process.THREAD_GROUP_TOP_APP);
42        super.run();
43    }
44
45    private static void ensureThreadLocked() {
46        if (sInstance == null) {
47            sInstance = new UiThread();
48            sInstance.start();
49            final Looper looper = sInstance.getLooper();
50            looper.setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER);
51            looper.setSlowDispatchThresholdMs(SLOW_DISPATCH_THRESHOLD_MS);
52            sHandler = new Handler(sInstance.getLooper());
53        }
54    }
55
56    public static UiThread get() {
57        synchronized (UiThread.class) {
58            ensureThreadLocked();
59            return sInstance;
60        }
61    }
62
63    public static Handler getHandler() {
64        synchronized (UiThread.class) {
65            ensureThreadLocked();
66            return sHandler;
67        }
68    }
69}
70