How to compare MotionEvent downtime to a clock, what is its time basis?

Question

I am trying to determine the chronological ordering of a MotionEvent vs something that happens periodically in my UI object.

private var rotateFinishTime: Long = -1
....
fun somethingHappensPeriodically() {
    Log.d(tag_, "show new round")
    ...
    this.rotateFinishTime = SystemClock.elapsedRealtime()
}

I have a GestureDetector.OnGestureListener attached:

   override fun onSingleTapConfirmed(gd: GestureDetector, e: MotionEvent): Boolean {
        // for tap: since it comes delayed, have to check event time
        if (e.downTime < this.rotateFinishTime || this.rotating) {
            Log.d(tag_, "e.downTime: $e.downTime rotateFinishTime: $rotateFinishTime downTime - rotateFinishTime: ${e.downTime - rotateFinishTime} rotating: $rotating")
            return true
        }
        ... do stuff
    }

e.downTime: 4763800 rotateFinishTime: 18832541 downTime - rotateFinishTime: -14068741 rotating: false

So the elapsed real-time doesn't seem to be the time basis. Obviously, unix epoch time doesn't fit either. Interesting note: the calculation produces the "expected" results on the qemu emulator, but not on my device with stock Android 6.0 flashed.

androidguy · Accepted Answer · 2017-10-30T02:31:35.260

I think I found it: I should call SystemClock.uptimeMillis() to make a valid comparison. The documentation is buried in InputEvent, they don't recite or repeat it on MotionEvent:

/** * Retrieve the time this event occurred, * in the {@link android.os.SystemClock#uptimeMillis} time base. * * @return Returns the time this event occurred, * in the {@link android.os.SystemClock#uptimeMillis} time base. */

Obviously, the emulator never went into deep sleep!

How to compare MotionEvent downtime to a clock, what is its time basis?

1 Answers1