Android5.1AlarmManagerService深入分析(Android4.4补充)

由于在我的博客中Android4.4已经比较详细的分析了AlarmManagerService,因此这里主要分析一下差异,在我看来5.1的在AlarmManagerService的改动还是比较大的。


先看AlarmManager新增了一个接口:

    public void setAlarmClock(AlarmClockInfo info, PendingIntent operation) {
        setImpl(RTC_WAKEUP, info.getTriggerTime(), WINDOW_EXACT, 0, operation, null, info);
    }

这个接口主要应用自己设置一个新的对象AlarmClockInfo,这个针对多用户的,每个用户也可以在AlarmManagerService中得到自己的下个AlarmClockInfo,可以得到triggertime,pendingIntent。

    public AlarmClockInfo getNextAlarmClock() {
        return getNextAlarmClock(UserHandle.myUserId());
    }


这是AlarmManager,接下来分析下AlarmManagerService中在5.1的变化。

先从Alarm的设置那块,也就是AlarmManagerService的主线程分析,主要变化最大的是rescheduleKernelAlarmsLocked函数

    void rescheduleKernelAlarmsLocked() {
        // Schedule the next upcoming wakeup alarm.  If there is a deliverable batch
        // prior to that which contains no wakeups, we schedule that as well.
        long nextNonWakeup = 0;
        if (mAlarmBatches.size() > 0) {
            final Batch firstWakeup = findFirstWakeupBatchLocked();
            final Batch firstBatch = mAlarmBatches.get(0);
            // always update the kernel alarms, as a backstop against missed wakeups
            if (firstWakeup != null) {
                mNextWakeup = firstWakeup.start;
                setLocked(ELAPSED_REALTIME_WAKEUP, firstWakeup.start);
            }
            if (firstBatch != firstWakeup) {//和唤醒的时间不相同,才赋值
                nextNonWakeup = firstBatch.start;
            }
        }
        if (mPendingNonWakeupAlarms.size() > 0) {//有没有发送的非唤醒类型的alarm
            if (nextNonWakeup == 0 || mNextNonWakeupDeliveryTime < nextNonWakeup) {
                nextNonWakeup = mNextNonWakeupDeliveryTime;
            }
        }
        // always update the kernel alarm, as a backstop against missed wakeups
        if (nextNonWakeup != 0) {
            mNextNonWakeup = nextNonWakeup;
            setLocked(ELAPSED_REALTIME, nextNonWakeup);
        }
    }

接下来主要分析下AlarmThread的run函数,主要用来发送alarm,直接挑选了主要内容:

                    boolean hasWakeup = triggerAlarmsLocked(triggerList, nowELAPSED, nowRTC);
                    if (!hasWakeup && checkAllowNonWakeupDelayLocked(nowELAPSED)) {//没有wakeup类型的alarm,而且允许延迟(接下来分析)
                        // if there are no wakeup alarms and the screen is off, we can
                        // delay what we have so far until the future.
                        if (mPendingNonWakeupAlarms.size() == 0) {
                            mStartCurrentDelayTime = nowELAPSED;
                            mNextNonWakeupDeliveryTime = nowELAPSED//定义下个alarm的发送时间
                                    + ((currentNonWakeupFuzzLocked(nowELAPSED)*3)/2);
                        }
                        mPendingNonWakeupAlarms.addAll(triggerList);
                        mNumDelayedAlarms += triggerList.size();
                        rescheduleKernelAlarmsLocked();
                        updateNextAlarmClockLocked();
                    } else {//当alarm有唤醒的
                        // now deliver the alarm intents; if there are pending non-wakeup
                        // alarms, we need to merge them in to the list.  note we don't
                        // just deliver them first because we generally want non-wakeup
                        // alarms delivered after wakeup alarms.
                        rescheduleKernelAlarmsLocked();
                        updateNextAlarmClockLocked();
                        if (mPendingNonWakeupAlarms.size() > 0) {//当有没有发送的非唤醒的alarm,加入发送列表一起发送
                            calculateDeliveryPriorities(mPendingNonWakeupAlarms);
                            triggerList.addAll(mPendingNonWakeupAlarms);
                            Collections.sort(triggerList, mAlarmDispatchComparator);
                            final long thisDelayTime = nowELAPSED - mStartCurrentDelayTime;
                            mTotalDelayTime += thisDelayTime;
                            if (mMaxDelayTime < thisDelayTime) {
                                mMaxDelayTime = thisDelayTime;
                            }
                            mPendingNonWakeupAlarms.clear();
                        }
                        deliverAlarmsLocked(triggerList, nowELAPSED);//发送的部分封装了一个函数,大致和以前一样就不分析了
                    }

下面我们详细分析下checkAllowNonWakeupDelayLocked这个函数:

    long currentNonWakeupFuzzLocked(long nowELAPSED) {
        long timeSinceOn = nowELAPSED - mNonInteractiveStartTime;
        if (timeSinceOn < 5*60*1000) {
            // If the screen has been off for 5 minutes, only delay by at most two minutes.
            return 2*60*1000;
        } else if (timeSinceOn < 30*60*1000) {
            // If the screen has been off for 30 minutes, only delay by at most 15 minutes.
            return 15*60*1000;
        } else {
            // Otherwise, we will delay by at most an hour.
            return 60*60*1000;
        }
    }

    boolean checkAllowNonWakeupDelayLocked(long nowELAPSED) {
        if (mInteractive) {//屏幕亮着
            return false;
        }
        if (mLastAlarmDeliveryTime <= 0) {
            return false;
        }
        if (mPendingNonWakeupAlarms.size() > 0 && mNextNonWakeupDeliveryTime > nowELAPSED) {//有非唤醒类型的alarm未发送,且发送没过期
            // This is just a little paranoia, if somehow we have pending non-wakeup alarms
            // and the next delivery time is in the past, then just deliver them all.  This
            // avoids bugs where we get stuck in a loop trying to poll for alarms.
            return false;
        }
        long timeSinceLast = nowELAPSED - mLastAlarmDeliveryTime;//现在距离上次发送的时间差
        return timeSinceLast <= currentNonWakeupFuzzLocked(nowELAPSED);//时间差小于灭屏到现在的一个时间差。
    }
接下来分析下,系统更新clockInfo那块。

    * Recomputes the next alarm clock for all users.
     */
    private void updateNextAlarmClockLocked() {
        if (!mNextAlarmClockMayChange) {
            return;
        }
        mNextAlarmClockMayChange = false;

        SparseArray nextForUser = mTmpSparseAlarmClockArray;
        nextForUser.clear();

        final int N = mAlarmBatches.size();
        for (int i = 0; i < N; i++) {
            ArrayList alarms = mAlarmBatches.get(i).alarms;
            final int M = alarms.size();

            for (int j = 0; j < M; j++) {
                Alarm a = alarms.get(j);
                if (a.alarmClock != null) {
                    final int userId = a.userId;

                    // Alarms and batches are sorted by time, no need to compare times here.
                    if (nextForUser.get(userId) == null) {
                        nextForUser.put(userId, a.alarmClock);//uid、alarmClock对应的关系
                    }
                }
            }
        }

        // Update mNextAlarmForUser with new values.
        final int NN = nextForUser.size();
        for (int i = 0; i < NN; i++) {
            AlarmManager.AlarmClockInfo newAlarm = nextForUser.valueAt(i);
            int userId = nextForUser.keyAt(i);
            AlarmManager.AlarmClockInfo currentAlarm = mNextAlarmClockForUser.get(userId);
            if (!newAlarm.equals(currentAlarm)) {//现在mNextAlarmClockForUser中uid对应的alarmclockinfo不是最新的,需要更新
                updateNextAlarmInfoForUserLocked(userId, newAlarm);
            }
        }

        // Remove users without any alarm clocks scheduled.
        final int NNN = mNextAlarmClockForUser.size();
        for (int i = NNN - 1; i >= 0; i--) {
            int userId = mNextAlarmClockForUser.keyAt(i);
            if (nextForUser.get(userId) == null) {//如果现在userId,对应的AlarmClockInfo没有,也要更新
                updateNextAlarmInfoForUserLocked(userId, null);
            }
        }
    }

    private void updateNextAlarmInfoForUserLocked(int userId,
            AlarmManager.AlarmClockInfo alarmClock) {
        if (alarmClock != null) {
            mNextAlarmClockForUser.put(userId, alarmClock);
        } else {          
            mNextAlarmClockForUser.remove(userId);
        }

        mPendingSendNextAlarmClockChangedForUser.put(userId, true);//将需要更新AlarmClockInfo的userId保存起来
        mHandler.removeMessages(AlarmHandler.SEND_NEXT_ALARM_CLOCK_CHANGED);
        mHandler.sendEmptyMessage(AlarmHandler.SEND_NEXT_ALARM_CLOCK_CHANGED);
    }

发送AlarmHandler.SEND_NEXT_ALARM_CLOCK_CHANGED消息,会调用如下函数:

    private void sendNextAlarmClockChanged() {
        SparseArray pendingUsers = mHandlerSparseAlarmClockArray;
        pendingUsers.clear();

        synchronized (mLock) {
            final int N  = mPendingSendNextAlarmClockChangedForUser.size();
            for (int i = 0; i < N; i++) {
                int userId = mPendingSendNextAlarmClockChangedForUser.keyAt(i);
                pendingUsers.append(userId, mNextAlarmClockForUser.get(userId));
            }
            mPendingSendNextAlarmClockChangedForUser.clear();
        }

        final int N = pendingUsers.size();
        for (int i = 0; i < N; i++) {
            int userId = pendingUsers.keyAt(i);
            AlarmManager.AlarmClockInfo alarmClock = pendingUsers.valueAt(i);
            Settings.System.putStringForUser(getContext().getContentResolver(),
                    Settings.System.NEXT_ALARM_FORMATTED,
                    formatNextAlarm(getContext(), alarmClock, userId),
                    userId);

            getContext().sendBroadcastAsUser(NEXT_ALARM_CLOCK_CHANGED_INTENT,
                    new UserHandle(userId));//发送广播通知各个用户下,其AlarmClockInfo已经改变
        }
    }

增加了一个监控屏幕亮灭屏的广播receiver:

    class InteractiveStateReceiver extends BroadcastReceiver {
        public InteractiveStateReceiver() {
            IntentFilter filter = new IntentFilter();
            filter.addAction(Intent.ACTION_SCREEN_OFF);
            filter.addAction(Intent.ACTION_SCREEN_ON);
            filter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);
            getContext().registerReceiver(this, filter);
        }

        @Override
        public void onReceive(Context context, Intent intent) {
            synchronized (mLock) {
                interactiveStateChangedLocked(Intent.ACTION_SCREEN_ON.equals(intent.getAction()));
            }
        }
    }

收到屏幕变化后会调用interactiveStateChangedLocked函数:

    void interactiveStateChangedLocked(boolean interactive) {
        if (mInteractive != interactive) {
            mInteractive = interactive;
            final long nowELAPSED = SystemClock.elapsedRealtime();
            if (interactive) {//亮屏,发送非唤醒类型的alarm
                if (mPendingNonWakeupAlarms.size() > 0) {
                    final long thisDelayTime = nowELAPSED - mStartCurrentDelayTime;
                    mTotalDelayTime += thisDelayTime;
                    if (mMaxDelayTime < thisDelayTime) {
                        mMaxDelayTime = thisDelayTime;
                    }
                    deliverAlarmsLocked(mPendingNonWakeupAlarms, nowELAPSED);
                    mPendingNonWakeupAlarms.clear();
                }
                if (mNonInteractiveStartTime > 0) {
                    long dur = nowELAPSED - mNonInteractiveStartTime;
                    if (dur > mNonInteractiveTime) {
                        mNonInteractiveTime = dur;
                    }
                }
            } else {//灭屏,更新mNonInteractiveStartTime 
                mNonInteractiveStartTime = nowELAPSED;
            }
        }
    }








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