protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            Window.AddFlags(WindowManagerFlags.KeepScreenOn);
            SetContentView(Resource.Layout.opencv_camera);

            _openCvCameraView            = FindViewById <CameraBridgeViewBase>(Resource.Id.surfaceView);
            _openCvCameraView.Visibility = ViewStates.Visible;
            _openCvCameraView.SetCvCameraViewListener(this);
            _openCV = new OpenCVServiceDroid();
        }
 protected override void OnDestroy()
 {
     base.OnDestroy();
     if (_openCvCameraView != null)
     {
         _openCvCameraView.DisableView();
         _openCvCameraView = null;
         _openCV           = null;
         rgba = null;
         roi  = null;
     }
 }