builder property
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;