ImageView: onDraw method draws "behind" the background of the image, not at the top

Here is the code for a simple ImageView extension that allows the user to draw with their finger.

public class MyImageView extends ImageView {

    List<Point> points = new ArrayList<Point>();
    Paint paint = new Paint();

    public MyImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public void onDraw(Canvas canvas) {
        for (Point point : points) {
            canvas.drawCircle(point.x, point.y, 5, paint);
            // Log.d(TAG, "Painting: "+point);
        }
        super.onDraw(canvas);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        super.onTouchEvent(event);
        Point point = new Point();
        point.x = event.getX();
        point.y = event.getY();
        points.add(point);
        invalidate();
        Log.d("", "point: " + point);
        return true;
    }

    class Point {
        float x, y;
        @Override
        public String toString() {
            return x + ", " + y;
        }
    }
}

This work is very good.

Now I want to use this code to paint at the top of the bitmap.

I used:

MyImageView ivPic = (MyImageView) dialog.findViewById(R.id.ivPic);
ivPic.setImageBitmap(picture);

But the picture is drawn “behind” the bitmap:

Do you have any ideas on how I can draw the "top" of a bitmap?