设定一个变量，实现导航栏的滚动和隐藏（变量的set方法中实现）

• (void)setIsExpand:(BOOL)isExpand
  {
  [UIView animateWithDuration:0.25 delay:0.0 usingSpringWithDamping:0.4 initialSpringVelocity:10.0 options:UIViewAnimationOptionTransitionCurlUp animations:^{
  [self.view layoutIfNeeded];
  } completion:^(BOOL finished) {
  self->_isExpand = isExpand;
  }];
  [self.navigationController setNavigationBarHidden:!isExpand animated:YES];

pragma clang diagnostic push

pragma clang diagnostic ignored"-Wdeprecated-declarations"

[[UIApplication sharedApplication] setStatusBarHidden:!isExpand withAnimation:NO];

pragma clang diagnostic pop

}