WakeupMessage.java revision e7636e47504034c048872f251a0a7cb240017b31 
1/*
2 * Copyright (C) 2015 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.internal.util;
18
19import android.app.AlarmManager;
20import android.content.Context;
21import android.os.Handler;
22import android.os.Message;
23
24import com.android.internal.annotations.VisibleForTesting;
25
26 /**
27 * An AlarmListener that sends the specified message to a Handler and keeps the system awake until
28 * the message is processed.
29 *
30 * This is useful when using the AlarmManager direct callback interface to wake up the system and
31 * request that an object whose API consists of messages (such as a StateMachine) perform some
32 * action.
33 *
34 * In this situation, using AlarmManager.onAlarmListener by itself will wake up the system to send
35 * the message, but does not guarantee that the system will be awake until the target object has
36 * processed it. This is because as soon as the onAlarmListener sends the message and returns, the
37 * AlarmManager releases its wakelock and the system is free to go to sleep again.
38 */
39public class WakeupMessage implements AlarmManager.OnAlarmListener {
40    private final AlarmManager mAlarmManager;
41
42    @VisibleForTesting
43    protected final Handler mHandler;
44    @VisibleForTesting
45    protected final String mCmdName;
46    @VisibleForTesting
47    protected final int mCmd, mArg1, mArg2;
48    private boolean mScheduled;
49
50    public WakeupMessage(Context context, Handler handler,
51            String cmdName, int cmd, int arg1, int arg2) {
52        mAlarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
53        mHandler = handler;
54        mCmdName = cmdName;
55        mCmd = cmd;
56        mArg1 = arg1;
57        mArg2 = arg2;
58    }
59
60    public WakeupMessage(Context context, Handler handler, String cmdName, int cmd, int arg1) {
61        this(context, handler, cmdName, cmd, arg1, 0);
62    }
63
64    public WakeupMessage(Context context, Handler handler, String cmdName, int cmd) {
65        this(context, handler, cmdName, cmd, 0, 0);
66    }
67
68    /**
69     * Schedule the message to be delivered at the time in milliseconds of the
70     * {@link android.os.SystemClock#elapsedRealtime SystemClock.elapsedRealtime()} clock and wakeup
71     * the device when it goes off. If schedule is called multiple times without the message being
72     * dispatched then the alarm is rescheduled to the new time.
73     */
74    public synchronized void schedule(long when) {
75        mAlarmManager.setExact(
76                AlarmManager.ELAPSED_REALTIME_WAKEUP, when, mCmdName, this, mHandler);
77        mScheduled = true;
78    }
79
80    /**
81     * Cancel all pending messages. This includes alarms that may have been fired, but have not been
82     * run on the handler yet.
83     */
84    public synchronized void cancel() {
85        if (mScheduled) {
86            mAlarmManager.cancel(this);
87            mScheduled = false;
88        }
89    }
90
91    @Override
92    public void onAlarm() {
93        // Once this method is called the alarm has already been fired and removed from
94        // AlarmManager (it is still partially tracked, but only for statistics). The alarm can now
95        // be marked as unscheduled so that it can be rescheduled in the message handler.
96        final boolean stillScheduled;
97        synchronized (this) {
98            stillScheduled = mScheduled;
99            mScheduled = false;
100        }
101        if (stillScheduled) {
102            Message msg = mHandler.obtainMessage(mCmd, mArg1, mArg2);
103            mHandler.handleMessage(msg);
104            msg.recycle();
105        }
106    }
107}
108