Chronometer Class that implements a simple timer
You can give it a start time in the elapsedRealtime() timebase, and it counts up from that, or if you don’t give it a base time, it will use the time at which you call start().
The timer can also count downward towards the base time by setting setCountDown(boolean) to true.
By default it will display the current timer value in the form “MM:SS” or “H:MM:SS”, or you can use setFormat(String) to format the timer value into an arbitrary string.
Usage of Chronometer