private void dimBackground(final float from, final float to) {
        final Window window = getWindow();
        ValueAnimator valueAnimator = ValueAnimator.ofFloat(from, to);
        valueAnimator.setDuration(500);
        valueAnimator.addUpdateListener(new AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                WindowManager.LayoutParams params = window.getAttributes();
                params.alpha = (Float) animation.getAnimatedValue();
getWindow().addFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
                window.setAttributes(params);
            }
        });

        valueAnimator.start();
    }