SystemClock.elapsedRealtime（）漂移时，该设备处于低功率模式 [英] SystemClock.elapsedRealtime() drift when the device is in low-power mode

问题描述

根据API文档，以及previous <一个href=\"http://stackoverflow.com/questions/4918192/android-timer-that-works-when-device-is-sleeping\">SO线程中， SystemClock.elapsedRealtime（）应该保持即使设备处于睡眠状态精确的时间。这不是我所观察到。

According to the API docs, as well as previous SO threads, SystemClock.elapsedRealtime() is supposed to keep accurate time even when the device is sleeping. This is not what I observe.

我写了一个简单的时钟它坐落在一个，而（真）循环和更新基于 SystemClock的价值在屏幕上的时间。 elapsedRealtime（）。如果我在两个装置，例如同步时钟通过NTP，然后进行切换屏幕打开和关闭的设备之一几次，显示的时间会漂移达±0.7秒。 （当手机没有连接到外接电源，因此睡眠模式是可能的罪魁祸首这里这只是发生）。

I have written a simple clock which sits in a while (true) loop and updates the time on screen based on the value of SystemClock.elapsedRealtime(). If I synchronize the clocks on two devices, e.g. via NTP, and then proceed to toggle the screen on and off a few times on one of the devices, the displayed time will drift by up to +/- 0.7 seconds. (This only happens when the phone isn't connected to external power, so sleep mode is the likely culprit here).

这是正常的吗？这是Android的一个bug？有什么办法通过睡眠/唤醒循环保持约20毫秒的计时精度？

Is this normal? Is this a bug in Android? Is there any way to keep ~20 millisecond timing accuracy through the sleep/wake cycles?

推荐答案

我一直有同样的问题，所以今晚我试图从改变我的计时​​方法SystemClock.elapsedRealtime（）到 System.currentTimeMillis的（）。到现在为止还挺好。当我点击关闭应用程序，回来的时候是不是漂流。结果
我曾与一个服务了Runnable进行了测试。我目前正在与Runnable接口测试它的主要活动和使用共享preFS存储一切，当应用程序失去焦点。
我还没有决定，其中这2种方法是最好的 - 但是在的currentTimeMillis 似乎不是从漂流时间问题遭受 elapsedRealtime 一样。

I have been having the same issue, so tonight I tried changing my timing method from SystemClock.elapsedRealtime() to System.currentTimeMillis(). So far so good. The time is not drifting when I click off the app and back.
I have tested it with the Runnable in a service. I am currently testing it with the Runnable in the main activity and using sharedprefs to store everything when the app loses focus. I haven't decided which of these 2 methods is best yet - but the currentTimeMillis seems to not suffer from the drifting time issue elapsedRealtime does.

我知道，谷歌不推荐使用的currentTimeMillis 定时的目的，但似乎它工作更好地为保持正确的时间，当应用程序失去焦点。

I know google doesn't recommend using currentTimeMillis for timing purposes, but it seems like it works better for keep correct time when the app loses focus.

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