Retrieve a reference to CountDownTimer after Closed activuty

My activity has a simple menuItem that start a counter... the counter is stored in a field of the activity the problem is with the "back button" after closing the activity (back button), the timer (as in my intention) continues, and restarting the activity behave correctly by reshowing the timer... but I lost the reference to the counter and so I cannot stop it Any ideas?

following there is a part of the code of the function boolean onOptionsItemSelected(MenuI开发者_Go百科tem item)

switch (item.getItemId()) {
    case R.id.STARTSTOP:
        running = !running;
        if (!running) {
            item.setTitle("START");
            if (counter!=null) {
                counter.cancel();
                counter = null;
            }
        }
        else {
            item.setTitle("STOP");
            counter = new CountDownTimer(1000*60*20/*20min*/,1000){
                @Override
                public void onFinish() {
                    TextView tv = (TextView) findViewById(R.id.counter);
                    tv.setText("done!");
                }
                @Override
                public void onTick(long millisUntilFinished) {
                    TextView tv = (TextView) findViewById(R.id.counter);
                    tv.setText(millisUntilFinished);
                    Log.d("XXXDEBUGXXX",millisUntilFinished);
                }
            };
            counter.start();
    }

}

I'd suggest to use AlarmManager instead.
Or you could use SharedPreferences to store intermediate value that's read in onResume(..) to restart the timer and saved in onPause(..).