Stopwatch class Null safety

A stopwatch which measures time while it's running.

A stopwatch is either running or stopped. It measures the elapsed time that passes while the stopwatch is running.

When a stopwatch is initially created, it is stopped and has measured no elapsed time.

The elapsed time can be accessed in various formats using elapsed, elapsedMilliseconds, elapsedMicroseconds or elapsedTicks.

The stopwatch is started by calling start.

Example:

final stopwatch = Stopwatch();
print(stopwatch.elapsedMilliseconds); // 0
print(stopwatch.isRunning); // false
stopwatch.start();
print(stopwatch.isRunning); // true

To stop or pause the stopwatch, use stop. Use start to continue again when only pausing temporarily.

stopwatch.stop();
print(stopwatch.isRunning); // false
Duration elapsed = stopwatch.elapsed;
await Future.delayed(const Duration(seconds: 1));
assert(stopwatch.elapsed == elapsed); // No measured time elapsed.
stopwatch.start(); // Continue measuring.

The reset method sets the elapsed time back to zero. It can be called whether the stopwatch is running or not, and doesn't change whether it's running.

// Do some work.
stopwatch.stop();
print(stopwatch.elapsedMilliseconds); // Likely > 0.
stopwatch.reset();
print(stopwatch.elapsedMilliseconds); // 0