Android: Using Canvas to draw on top of a bitmap

So I have a bitmap (called imgBitmap) that is displayed in a custom imageview. When the user double clicks, I want a circle to appear on top of the image where they are clicking. With the following code, the original bitmap gets deleted and there is just a circle on the screen. How do I make it so the circle is drawn but the original bitmap is still there?

  @Override
    public boolean onDoubleTap(MotionEvent event) {


        Bitmap bmOverlay = Bitmap.createBitmap(getWidth(),
               getHeight(),
                imgBitmap.getConfig());
        Canvas canvas = new Canvas(bmOverlay);
        Paint p = new Paint();
        p.setAntiAlias(true);
        p.setColor(Color.RED);
        p.setStrokeWidth(2);
        p.setStyle(Paint.Style.STROKE);
        canvas.drawBitmap(bmOverlay, matrix, background);
        canvas.drawCircle((int)event.getX(),(int)event.getY(),
                15, p);
        setImageBitmap(bmOverlay);
        return true;
    }


    @Override
    public boolean onDown(MotionEvent e) {
        return false;
    }
}