requestTwoLevel method
make the header enter refreshing state,and callback onRefresh
Implementation
Future<void> requestTwoLevel({Duration duration = const Duration(milliseconds: 300), Curve curve = Curves.linear}) {
assert(position != null, 'Try not to call requestRefresh() before build,please call after the ui was rendered');
headerMode!.value = RefreshStatus.twoLevelOpening;
return Future.delayed(const Duration(milliseconds: 50)).then((_) async {
await position?.animateTo(position!.minScrollExtent, duration: duration, curve: curve);
});
}