Xamarin Countdown Problem

Simple.cs

public class Simple : CountDownTimer
        {
            event TickHandler _onTick;
            event TickHandler _onFinished;

            public event TickHandler OnTicked
            {
                add { _onTick += value; }
                remove { _onTick -= value; }
            }


            public event TickHandler OnFinished
            {
                add { _onFinished += value; }
                remove { _onFinished -= value; }
            }

            public delegate void TickHandler(object sender, TickEventArgs args);


            public Simple(long totalTime, long interval):base(totalTime, interval)
            {
            }


            public override void OnFinish()
            {
                if (_onFinished != null)
                {
                    _onFinished(this, new TickEventArgs() { TimeRemaining = 0 });
                }
            }

            public override void OnTick(long millisUntilFinished) {
                if (_onTick != null)
                {
                    _onTick(this, new TickEventArgs() { TimeRemaining = millisUntilFinished });
                }
            }

        }

TimerActivity.cs

[Activity(Label = "TimerActivity")]
    public class TimerActivity : Activity
    {
        static int _totalTime = 1000 * 10; // 1000 * 60 * 25;
        static int _interval = 1000 * 1;



        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);


            SetContentView(Resource.Layout.Timer);


            var textView1 = FindViewById<TextView>(Resource.Id.textView1);

            var timer = new Simple(_totalTime, _interval);

            textView1.Text = "Started";

            timer.OnTicked += (sender, args) =>
            {
                RunOnUiThread(() =>
                {
                    textView1.Text = args.TimeRemaining.ToString(); //args.TimeRemaining.ToString();
                });
            };

            timer.OnFinished += (sender, args) =>
            {
                RunOnUiThread(() =>
                {
                    textView1.Text = "Finished"; //args.TimeRemaining.ToString();

                });
            };


            timer.Start();

            // Create your application here
        }