Android Studio Timer Show Textview

Timer.java

    private TextView timenow;
    private TextView datenow;
    private Handler handler = new Handler();
    private String formatString="";
    
    public View onCreate(){
      handler.removeCallbacks(updateTimeTask);
      handler.postDelayed(updateTimeTask, 1000);
    }
    
    private Runnable updateTimeTask = new Runnable() {
        public void run() {
            updateTime();
            handler.postDelayed(this, 1000);
        }
    };

    private void updateTime() {
        final Date currentTime = new Date(System.currentTimeMillis());
        if (formatString.equals("HH:mm")){
            formatString = "HH mm";
        }else{
            formatString = "HH:mm";
        }
        final SimpleDateFormat formatterTime = new SimpleDateFormat( formatString );
        timenow.setText( formatterTime.format(currentTime) );
        final SimpleDateFormat formatterDate = new SimpleDateFormat( "EEE, dd MMM yyyy" );
        datenow.setText( formatterDate.format(currentTime) );
    }

    @Override
    public void onStop() {
        super.onStop();
        handler.removeCallbacks(updateTimeTask);
    }

    @Override
    public void onResume() {
        super.onResume();
        handler.removeCallbacks(updateTimeTask);
        handler.postDelayed(updateTimeTask, 1000);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        if ( handler != null )
            handler.removeCallbacks(updateTimeTask);
        handler = null;
    }