如果未启用自动时钟，如何知道本地时间与 android 设备之间的时差？ 我以编程方式需要它

Question

I have a blockchain api with correct time, but when some android devices where the users themselves set their time (auto-clock is not enabled), I am having problem with working with this api because of the difference between these two times. Could you help me to identity this difference? System.currrentMillisSecond() method is returning the time set by the user.

Answer 1

You don't have other way than syncing with 3rd-party, getting current time from eg own server-side or some web service and counting time basing on it. You may calculate diff between "real-time" and "on-device-time", but still user can minimalize your app and during it's work ( Service in background?) can change again locally set time

Note that there is also SystemClock.elapsedRealtime() which returns elapsed time since last boot. This can't be changed by user during runtime (only by restarting device), so may be helpful for counting difference

val synced = getTimestampFromWeb() // instead of unreliable System.currrentMillisSecond()
val elapsedWhenSynced = SystemClock.elapsedRealtime()
// store these in some 
...
// use below line anytime later 
val currentTime = synced + (SystemClock.elapsedRealtime() - elapsedWhenSynced)