})
    : this._cardBuilder = cardBuilder,
      this._totalNum = totalNum,
      assert(stackNum &gt; 1),
      this._stackNum = stackNum,
      assert(maxWidth &gt; minWidth &amp;&amp; maxHeight &gt; minHeight)
&#47;&#47;        this._maxWidth = maxWidth,
&#47;&#47;        this._minWidth = minWidth,
&#47;&#47;        this._maxHeight = maxHeight,
&#47;&#47;        this._minHeight = minHeight
{
  double widthGap = maxWidth - minWidth;
  double heightGap = maxHeight - minHeight;

  _cardAligns = new List();
 