@property(nonatomic,assign) BOOL automaticallyAdjustsScrollViewInsets

@property(nonatomic) UIScrollViewContentInsetAdjustmentBehavior contentInsetAdjustmentBehavior //这个属性是一个枚举类型的
{
UIScrollViewContentInsetAdjustmentAutomatic,//scrollView会自动计算和适应顶部和底部的内边距并且在scrollView 不可滚动时,也会设置内边距.
UIScrollViewContentInsetAdjustmentScrollableAxes, //自动适应边距
UIScrollViewContentInsetAdjustmentNever， //和 automaticallyAdjustsScrollViewInsets=NO有着同样的效果，不计算内边距
UIScrollViewContentInsetAdjustmentAlways//根据safeAreaInsets （安全区域）计算内边距
 }

 self.tableView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;

if (@available(iOS 11.0, *)) {
 [[UIScrollView appearance] setContentInsetAdjustmentBehavior:UIScrollViewContentInsetAdjustmentNever];
}