Punch a hole in a rectangle overlay with HW acceleration enabled on View

Instead of allocating a new canvas on each repaint, you should be able to allocate it once and then reuse the canvas on each repaint.

on init and on resize:

Bitmap b = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(b);

on repaint:

b.eraseColor(Color.TRANSPARENT);
    // needed if backColor is not opaque; thanks @JosephEarl
c.drawColor(backColor);
c.drawCircle(cx, cy, radius, eraser);

canvas.drawBitmap(b, 0, 0, null);