TwoLevelList({Key key, Key scrollableKey, List<Widget> children: const [], MaterialListType type: MaterialListType.twoLine, EdgeInsets padding })

Creates a scrollable list of items that can expand and collapse.

The type argument must not be null.

Source 

TwoLevelList({
  Key key,
  this.scrollableKey,
  this.children: const <Widget>[],
  this.type: MaterialListType.twoLine,
  this.padding
}) : super(key: key) {
  assert(type != null);
}