builder property

Widget Function(BuildContext context, double fraction, Widget? child) builder
final

A builder that is called whenever the scroll offset changes.

fraction is a double between 0.0 and 1.0 that represents how much of the scrolling towards the threshold has been done. For example, if threshold is given as 100.0 and the current scroll offset is 25.0, fraction will be 0.25.

Implementation

final Widget Function(
  BuildContext context,
  double fraction,
  Widget? child,
) builder;