CupertinoNavigationBarBackButton constructor

const CupertinoNavigationBarBackButton({@required Color color, String previousPageTitle })

Construct a CupertinoNavigationBarBackButton that can be used to pop the current route.

The color parameter must not be null.

Implementation 

const CupertinoNavigationBarBackButton({
  @required this.color,
  this.previousPageTitle,
}) : _backChevron = null,
     _backLabel = null,
     assert(color != null);