iOS 隐藏导航栏后，UITableView向下偏移状态栏高度

    if (@available(iOS 11.0, *)) {
        self.mainTableView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
    } else {
        self.automaticallyAdjustsScrollViewInsets = NO;
    }