android how to make popupwindow background blur

PopupWindow popup = new PopupWindow(contentView, width, height);

popup.setBackgroundDrawable(background);
popup.showAsDropDown(anchor);

View container = (View) popup.getContentView().getParent();
WindowManager wm = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
WindowManager.LayoutParams p = (WindowManager.LayoutParams) container.getLayoutParams();

// add flag
p.flags |= WindowManager.LayoutParams.FLAG_DIM_BEHIND;
p.dimAmount = 0.3f;

wm.updateViewLayout(container, p);