java - 'setExact' 和 'setAlarmClock' 之间的区别

Question

在我应该在指定时间触发警报的应用程序中，警报的目的是通过 Notification 通知用户，我对获得不精确的结果感到绝望。闹钟响了，但不是在指定的时间。当警报设置和它应该响起的时间之间的时间很长时，这是系统性的。为此，我使用了 setExact(RTC_WAKEUP,time,intent)。经过多次尝试使其工作后，我终于看到并尝试了 setAlarmClock 函数，一切顺利!!

根据 javadoc，setAlarmClock 与 setExact 相同，只是它隐含了 RTC_WAKEUP。据我所知，至少存在另一个差异。有人知道吗？

Answer 1

setExact()和 setAlarmClock()两者都对 setImpl() 进行了非常相似的调用.如果您对 setExact() 调用使用 RTC_WAKEUP，唯一的区别是 AlarmClockInfo 类型的最终参数。

在服务端，在set()中收到调用.在该方法的末尾，我们可以看到额外参数带来的不同:

@Override
public void set(int type, long triggerAtTime, long windowLength, long interval, int flags,
        PendingIntent operation, WorkSource workSource,
        AlarmManager.AlarmClockInfo alarmClock) {
    final int callingUid = Binder.getCallingUid();
    if (workSource != null) {
        getContext().enforcePermission(
                android.Manifest.permission.UPDATE_DEVICE_STATS,
                Binder.getCallingPid(), callingUid, "AlarmManager.set");
    }

    // No incoming callers can request either WAKE_FROM_IDLE or
    // ALLOW_WHILE_IDLE_UNRESTRICTED -- we will apply those later as appropriate.
    flags &= ~(AlarmManager.FLAG_WAKE_FROM_IDLE
            | AlarmManager.FLAG_ALLOW_WHILE_IDLE_UNRESTRICTED);

    // Only the system can use FLAG_IDLE_UNTIL -- this is used to tell the alarm
    // manager when to come out of idle mode, which is only for DeviceIdleController.
    if (callingUid != Process.SYSTEM_UID) {
        flags &= ~AlarmManager.FLAG_IDLE_UNTIL;
    }

    // If the caller is a core system component, and not calling to do work on behalf
    // of someone else, then always set ALLOW_WHILE_IDLE_UNRESTRICTED.  This means we
    // will allow these alarms to go off as normal even while idle, with no timing
    // restrictions.
    if (callingUid < Process.FIRST_APPLICATION_UID && workSource == null) {
        flags |= AlarmManager.FLAG_ALLOW_WHILE_IDLE_UNRESTRICTED;
    }

    // If this is an exact time alarm, then it can't be batched with other alarms.
    if (windowLength == AlarmManager.WINDOW_EXACT) {
        flags |= AlarmManager.FLAG_STANDALONE;
    }

    // If this alarm is for an alarm clock, then it must be standalone and we will
    // use it to wake early from idle if needed.
    if (alarmClock != null) {
        flags |= AlarmManager.FLAG_WAKE_FROM_IDLE | AlarmManager.FLAG_STANDALONE;
    }

    setImpl(type, triggerAtTime, windowLength, interval, operation,
            flags, workSource, alarmClock, callingUid);
}

如果有一个非空的 alarmClock 参数，请求会在 FLAG_STANDALONE 之上获得 FLAG_WAKE_FROM_IDLE 标志，您将获得在这两种情况下。以及 FLAG_WAKE_FROM_IDLE 的评论说:

Flag for alarms: this alarm would like to wake the device even if it is idle. This is, for example, an alarm for an alarm clock.

如果你愿意，可以dig into the usage of FLAG_WAKE_FROM_IDLE ——但据我所知，这就是区别。您的“正常”确切警报不会将设备从空闲状态唤醒，但使用 setAlarmClock() 设置的警报会。