CupertinoSliverRefreshControl constructor Null safety

const CupertinoSliverRefreshControl(
  1. {Key? key,
  2. double refreshTriggerPullDistance = _defaultRefreshTriggerPullDistance,
  3. double refreshIndicatorExtent = _defaultRefreshIndicatorExtent,
  4. RefreshControlIndicatorBuilder? builder = buildRefreshIndicator,
  5. RefreshCallback? onRefresh}

Create a new refresh control for inserting into a list of slivers.

The refreshTriggerPullDistance and refreshIndicatorExtent arguments must not be null and must be >= 0.

The builder argument may be null, in which case no indicator UI will be shown but the onRefresh will still be invoked. By default, builder shows a CupertinoActivityIndicator.

The onRefresh argument will be called when pulled far enough to trigger a refresh.


const CupertinoSliverRefreshControl({
  this.refreshTriggerPullDistance = _defaultRefreshTriggerPullDistance,
  this.refreshIndicatorExtent = _defaultRefreshIndicatorExtent,
  this.builder = buildRefreshIndicator,
}) : assert(refreshTriggerPullDistance != null),
     assert(refreshTriggerPullDistance > 0.0),
     assert(refreshIndicatorExtent != null),
     assert(refreshIndicatorExtent >= 0.0),
       refreshTriggerPullDistance >= refreshIndicatorExtent,
       'The refresh indicator cannot take more space in its final state '
       'than the amount initially created by overscrolling.',