'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，我终于看到并尝试了 setAlarmClock 功能，一切顺利！！

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

Answer 1

setExact() and setAlarmClock() both make very similar calls to setImpl()。如果您将 RTC_WAKEUP 用于 setExact() 调用，唯一的区别是类型为 AlarmClockInfo.

的最终参数

在服务端，在set()接到电话。在该方法的末尾，我们可以看到额外参数的不同之处：

@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);
}

如果存在非空 alarmClock 参数，请求将在 FLAG_STANDALONE 之上获得 FLAG_WAKE_FROM_IDLE 标志，在这两种情况下您都会获得。 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，你可以 dig into the usage of FLAG_WAKE_FROM_IDLE -- 但据我所知，这就是区别。您的 "normal" 确切的闹钟不会将设备从空闲状态唤醒，但使用 setAlarmClock() 设置的闹钟会。

Answer 2

Doze mode, introduced in Android 6.0 (API level 23), adds further restrictions to those outlined above: (TL;DR: only setAlarmClock triggers in doze mode, and )

Doze restrictions

The following restrictions apply to your apps while in Doze: [...]

The system ignores wake locks.

Standard AlarmManager alarms (including setExact() and setWindow()) are deferred to the next maintenance window.

If you need to set alarms that fire while in Doze, use setAndAllowWhileIdle() or setExactAndAllowWhileIdle().

Alarms set with setAlarmClock() continue to fire normally — the system exits Doze shortly before those alarms fire. [...]

设备进入低功耗休眠状态，并定期唤醒以执行其他警报等

'setExact' 和 'setAlarmClock' 之间的区别

Difference between 'setExact' and 'setAlarmClock'

java

android

alarm

Doze restrictions