refreshIndicatorExtent property
final
The amount of space the refresh indicator sliver will keep holding while onRefresh's Future is still running.
Must be a positive number, but can be zero, in which case the sliver will start retracting back to zero as soon as the refresh is started. Defaults to 60 pixels when not specified.
Must be smaller than refreshTriggerPullDistance, since the sliver shouldn't grow further after triggering the refresh.
Implementation
final double refreshIndicatorExtent;