[mono-android] SurfaceView keeps disappearing when I try to get the colour that is on it (creating a colorpicker)

[Paul Johnson]

Hi,

I'm creating a colorpicker for an art app but have hit a problem. I've
created a view that is consists of a linearview (horizontal) with a
pile of surfaceviews. Each surfaceview has an gradient fill set as the
background. Under that is an imageview that displays the colour I've
clicked on.

The problem is this. If I click on the first SurfaceView, the colour
appears in the imageview. If I click on any other SurfaceView it will
either switch places with the first SurfaceView *or* vanish
completely. The ImageView turns black.

The code I have looks like this

8-->
    public class colorPicker : Activity, ISurfaceHolderCallback,
View.IOnTouchListener
    {
        ImageView imageView;

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            SetContentView(Resource.Layout.colorPicker);

            SurfaceView surfaceCP1 =
FindViewById<SurfaceView>(Resource.Id.colorPick1);
            var holderCP1 = surfaceCP1.Holder;
            holderCP1.AddCallback(this);
            surfaceCP1.SetOnTouchListener(this);

            SurfaceView surfaceCP2 =
FindViewById<SurfaceView>(Resource.Id.colorPick2);
            var holderCP2 = surfaceCP2.Holder;
            holderCP2.AddCallback(this);
            surfaceCP2.SetOnTouchListener(this);

            SurfaceView surfaceCP3 =
FindViewById<SurfaceView>(Resource.Id.colorPick3);
            var holderCP3 = surfaceCP3.Holder;
            holderCP3.AddCallback(this);
            surfaceCP3.SetOnTouchListener(this);

            SurfaceView surfaceCP4 =
FindViewById<SurfaceView>(Resource.Id.colorPick4);
            var holderCP4 = surfaceCP4.Holder;
            holderCP4.AddCallback(this);
            surfaceCP4.SetOnTouchListener(this);

            SurfaceView surfaceCP5 =
FindViewById<SurfaceView>(Resource.Id.colorPick5);
            var holderCP5 = surfaceCP5.Holder;
            holderCP5.AddCallback(this);
            surfaceCP5.SetOnTouchListener(this);

            SurfaceView surfaceCP6 =
FindViewById<SurfaceView>(Resource.Id.colorPick6);
            var holderCP6 = surfaceCP6.Holder;
            holderCP6.AddCallback(this);
            surfaceCP6.SetOnTouchListener(this);

            SurfaceView surfaceCP7 =
FindViewById<SurfaceView>(Resource.Id.colorPick7);
            var holderCP7 = surfaceCP7.Holder;
            holderCP7.AddCallback(this);
            surfaceCP7.SetOnTouchListener(this);

            SurfaceView surfaceCP8 =
FindViewById<SurfaceView>(Resource.Id.colorPick8);
            var holderCP8 = surfaceCP8.Holder;
            holderCP8.AddCallback(this);
            surfaceCP8.SetOnTouchListener(this);

            SurfaceView surfaceCP9 =
FindViewById<SurfaceView>(Resource.Id.colorPick9);
            var holderCP9 = surfaceCP9.Holder;
            holderCP9.AddCallback(this);
            surfaceCP9.SetOnTouchListener(this);

            SurfaceView surfaceCP10 =
FindViewById<SurfaceView>(Resource.Id.colorPick10);
            var holderCP10 = surfaceCP10.Holder;
            holderCP10.AddCallback(this);
            surfaceCP10.SetOnTouchListener(this);

            SurfaceView surfaceCP11 =
FindViewById<SurfaceView>(Resource.Id.colorPick11);
            var holderCP11 = surfaceCP11.Holder;
            holderCP11.AddCallback(this);
            surfaceCP11.SetOnTouchListener(this);

            SurfaceView surfaceCP12 =
FindViewById<SurfaceView>(Resource.Id.colorPick12);
            var holderCP12 = surfaceCP12.Holder;
            holderCP12.AddCallback(this);
            surfaceCP12.SetOnTouchListener(this);

            imageView = FindViewById<ImageView>(Resource.Id.colorDisplay);
            imageView.SetBackgroundColor(Android.Graphics.Color.Red);
        }

        public bool OnTouch(View v, MotionEvent e)
        {
            int sv = v.Id;
            int x = (int) e.GetX();
            int y = (int) e.GetY();
            double xbuf = 0;
            double SizeX = (WindowManager.DefaultDisplay.Width / 12);
            switch (sv)
            {
                case Resource.Id.colorPick1: xbuf = 0;
                    break;
                case Resource.Id.colorPick2: xbuf = SizeX;
                    break;
                case Resource.Id.colorPick3: xbuf = SizeX * 2;
                    break;
                case Resource.Id.colorPick4: xbuf = SizeX * 3;
                    break;
                case Resource.Id.colorPick5: xbuf = SizeX * 4;
                    break;
                case Resource.Id.colorPick6: xbuf = SizeX * 5;
                    break;
                case Resource.Id.colorPick7: xbuf = SizeX * 6;
                    break;
                case Resource.Id.colorPick8: xbuf = SizeX * 7;
                    break;
                case Resource.Id.colorPick9: xbuf = SizeX * 8;
                    break;
                case Resource.Id.colorPick10: xbuf = SizeX * 9;
                    break;
                case Resource.Id.colorPick11: xbuf = SizeX * 10;
                    break;
                case Resource.Id.colorPick12: xbuf = SizeX * 11;
                    break;
            }
#if DEBUG
            Console.WriteLine("X = {0}, Y = {1}, sv = {2}, xbuf =
{3}", x, y, sv, xbuf);
#endif
            Bitmap b = Bitmap.CreateBitmap(v.Width, v.Height,
Bitmap.Config.Argb8888);
            Canvas c = new Canvas(b);
            v.Layout(0, 0, v.Width, v.Height);
            v.Draw(c);
            int color = b.GetPixel(x, y);
#if DEBUG
            Console.WriteLine("color = {0}", color);
#endif
            imageView.SetBackgroundColor(Color.Argb(255,
Color.GetRedComponent(color), Color.GetGreenComponent(color),
Color.GetBlueComponent(color)));
            return false;
        }
<--8

The switch is in the second method as an attempt to position the
canvas correctly ie  v.Layout((int)xbuf, 0, v.Width, v.Height).

Additional to this, is there a way to display the colour under the
pointer as the pointer moves?

Thanks

Paul