askPermission method Null safety

Future<void> askPermission(
  1. Future<bool?> onRationaleNotAvailable(
      )
    )

    Implementation

    Future<void> askPermission(
  Future<bool?> Function() onRationaleNotAvailable,
) async {
  final bool showRationale = await permission.shouldShowRequestRationale;

  if (showRationale) {
    _onNewPermissionStatus(await permission.request());
  } else {
    final bool? shouldOpenSettings = await onRationaleNotAvailable.call();

    if (shouldOpenSettings == true) {
      await openAppSettings();
      return checkPermission();
    }
  }
}