Show popupwindow with dim background

DimPopupWIndow.kt

fun PopupWindow.dimBehind(dim: Float = 0.3f) {
      val container: View = contentView.rootView
      val context = contentView.context
      val wm = context.getSystemService(Context.WINDOW_SERVICE) as WindowManager;
      val p = container.layoutParams as WindowManager.LayoutParams;
      p.flags = p.flags or WindowManager.LayoutParams.FLAG_DIM_BEHIND; // add a flag here instead of clear others
      p.dimAmount = dim
      wm.updateViewLayout(container, p);
  }