code: public DialogPlusBuilder setMargin(int left, int top, int right, int bottom) {
      this.margin[0] = left;
      this.margin[1] = top;
      this.margin[2] = right;
      this.margin[3] = bottom;
      return this;
    }
docs: Add margins to your dialog. They are set to 0 except when gravity is center. In that case basic margins
  are applied