java.lang.NullPointerException: Attempt to invoke virtual method 'void com.hhl.library.FlowTagLayout

实际情况是你按照 一般的 findViewbyId(R.id.orientation_layout); 已经得不到 ID了，会报空指针的 

popup = new PopupWindow(this);View popView = LayoutInflater.from(this).inflate(R.layout.listings_search, null);

所以 你在得到ID的时候应该 加上  PopupWindow 布局view的引用

orientationLayout = (FlowTagLayout) popView.findViewById(R.id.orientation_layout);