WakeupMessage.java revision 4171cdf303c24704c2412653fd0eccb21a487e8e 
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    @VisibleForTesting
49    protected final Object mObj;
50    private boolean mScheduled;
51
52    public WakeupMessage(Context context, Handler handler,
53            String cmdName, int cmd, int arg1, int arg2, Object obj) {
54        mAlarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
55        mHandler = handler;
56        mCmdName = cmdName;
57        mCmd = cmd;
58        mArg1 = arg1;
59        mArg2 = arg2;
60        mObj = obj;
61    }
62
63    public WakeupMessage(Context context, Handler handler, String cmdName, int cmd, int arg1) {
64        this(context, handler, cmdName, cmd, arg1, 0, null);
65    }
66
67    public WakeupMessage(Context context, Handler handler,
68            String cmdName, int cmd, int arg1, int arg2) {
69        this(context, handler, cmdName, cmd, arg1, arg2, null);
70    }
71
72    public WakeupMessage(Context context, Handler handler, String cmdName, int cmd) {
73        this(context, handler, cmdName, cmd, 0, 0, null);
74    }
75
76    /**
77     * Schedule the message to be delivered at the time in milliseconds of the
78     * {@link android.os.SystemClock#elapsedRealtime SystemClock.elapsedRealtime()} clock and wakeup
79     * the device when it goes off. If schedule is called multiple times without the message being
80     * dispatched then the alarm is rescheduled to the new time.
81     */
82    public synchronized void schedule(long when) {
83        mAlarmManager.setExact(
84                AlarmManager.ELAPSED_REALTIME_WAKEUP, when, mCmdName, this, mHandler);
85        mScheduled = true;
86    }
87
88    /**
89     * Cancel all pending messages. This includes alarms that may have been fired, but have not been
90     * run on the handler yet.
91     */
92    public synchronized void cancel() {
93        if (mScheduled) {
94            mAlarmManager.cancel(this);
95            mScheduled = false;
96        }
97    }
98
99    @Override
100    public void onAlarm() {
101        // Once this method is called the alarm has already been fired and removed from
102        // AlarmManager (it is still partially tracked, but only for statistics). The alarm can now
103        // be marked as unscheduled so that it can be rescheduled in the message handler.
104        final boolean stillScheduled;
105        synchronized (this) {
106            stillScheduled = mScheduled;
107            mScheduled = false;
108        }
109        if (stillScheduled) {
110            Message msg = mHandler.obtainMessage(mCmd, mArg1, mArg2, mObj);
111            mHandler.handleMessage(msg);
112            msg.recycle();
113        }
114    }
115}
116