docs: public Dialog dimAmount(float amount){
          Window window = getWindow();
          if(amount > 0f){
              window.addFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
              WindowManager.LayoutParams lp = window.getAttributes();
              lp.dimAmount = amount;
              window.setAttributes(lp);
          }
          else
              window.clearFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
          return this;
      }