onLoad property
Load callback.
Triggered on load.
When null, disable load.
The Footer current state is IndicatorMode.processing.
More see IndicatorNotifier._onTask.
The return value can be IndicatorResult,
the default processing result is IndicatorResult.success,
and IndicatorResult.fail when an exception occurs.
When EasyRefreshController.controlFinishLoad is true,
the return value is invalid.
Implementation
final FutureOr Function()? onLoad;