use ApplicationExitInfo to retrieve lastAppAliveElapsedTimeMillis

[joshskeen]

Using shared preferences with a 1 second interval causes a lot of reads/writes to disk, retrieve elapsed time millis from ApplicationExitInfo.

val am = context.getSystemService(Context.ACTIVITY_SERVICE) as ActivityManager
val applicationExitInfos: List<ApplicationExitInfo> = am.getHistoricalProcessExitReasons(null, 0, 0)
applicationExitInfos.first().timestamp