Chronometer timer does not stop

Question

I have a chronometer timer on a fragment and I want it to reset to 00:00 and stops when I press a button.

Here is the code of the fragment:

public class FirstFragment extends Fragment {

    Chronometer chronometer;

    @Overried
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        final View view = inflater.inflate(R.layout.fragment_memo, container, false);
        Button testButton = view.findViewById(R.id.btn_test);
        chronometer = view.findViewById(R.id.stop_watch);
        chronometer.setFormat("%s");

        testButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                stopStopWatch();

                ((BottomNavigationView) getActivity().findViewById(R.id.bottom_navigation))
                    .setSelectedItemId(R.id.nav_second_fragment);

            }
        });

    }
}

And I made a class called StopWatchHelper (Thanks to @Mushahid)

public class StopWatchHelper {

    @Nullable
    private static Long startTime;

    @Nullable
    public Long getStartTime() {

        return startTime;

    }

    public void setStartTime(final long startTime) {

        this.startTime = startTime;

    }

}

And here are my start and stop methods for the chronometer:

private void startStopWatch() {

    StopWatchHelper stopWatchHelper = new StopWatchHelper();

    if (stopWatchHelper.getStartTime() == null) {

        long startTime = SystemClock.elapsedRealtime();

        stopWatchHelper.setStartTime(startTime);
        chronometer.setBase(startTime);

    } else {

        chronometer.setBase(stopWatchHelper.getStartTime());

    }

    chronometer.start();

}

private void stopStopWatch() {

    StopWatchHelper stopWatchHelper = new StopWatchHelper();
    long startTime = SystemClock.elapsedRealtime();
    stopWatchHelper.setStartTime(startTime);
    chronometer.setBase(startTime);
    chronometer.stop();

}

So the problem is that the timer never stops even if I call the stopStopWatch() method.

It definitely has chronometer.stop(); inside of it, but why does it happen?

The timer resets to 00:00 properly but it keeps counting after the stop method is called.

Is it because it is inside a fragment?

Can anyone help me with this? Thank you.