public override void DismissProgressDialog()
 {
     _controller.BeginInvokeOnMainThread (() => {
         if (_progressDialog != null) {
             _progressDialog.Dispose();
             _progressDialog = null;
         }
     });
 }
        public override void ShowProgressDialog(string message)
        {
            _controller.BeginInvokeOnMainThread(() => {
                if(_progressDialog != null) {
                    _progressDialog.Dispose();
                    _progressDialog = null;
                }

                _progressDialog = new CustomActivityIndicator(message);
                _progressDialog.Show();
            });
        }