Android timer that works when device is sleeping
I've got a partial solution to my original post above. It doesn't yet address the clock drift associated with the time spent in calculations during the postDelayed() processing, but it is a step forward. In addition, it's deceptively simple, always a good sign.
It turns out I was using SystemClock.uptimeMillis() when I should have been using SystemClock.elapsedRealtime(). The difference between the 2 is subtle, but important.
As you might expect, my solution keeps track of elapsed time by accumulating durations between calls to postDelayed() - i.e., elapsed time = elapsedTime + lastClockInterval. As stated above, the original implementation used uptimeMillis(). Careful reading of the javadoc reveals that uptimeMillis() doesn't include time spent in "deep sleep", e.g., when the user presses the power button. But the elapsedRealtime() method does include time spent in "deep sleep" mode. All that was required to track time across deep sleep cycles was to replace the use of uptimeMillis() with elapsedRealtime(). Success! No need to use AlarmManager, PartialWakeLock, or anything else substantially more complicated. Granted, these methods still have uses, but they are overkill when implementing a simple elapsed-time clock or timer.
The next problem to tackle is with the clock-drift caused by the non-zero execution time associated with postDelayed() processing. I'm hoping that spawning a thread to do the processing will address this issue, allowing postDelayed() to more or less mimic an asynchronous call. Another approach would be to adjust the postDelayed() delay time to take into account the time spent in postDelayed(). I'll post my results.
On an unrelated note, during my investigation I treated myself to a CommonsWare Warescription. While I didn't directly use any ideas from this source for this problem, I do think that it is going to be my Android go-to information source for the foreseeable future. I've got an O'Reilly subscription through my day job, but I've found the CommonsWare books to be as least as good, if not better, source of information about Android development as the O'Reilly resources. And I have found the O'Reilly Safari resources to be pretty good. Interesting...
Cheers, Rich