一般是两个原因:
1、UIScrollView的偏移
if (@available(iOS 11, *)) { UIScrollView.appearance.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever; }
2、导航栏的毛玻璃效果
controller.navigationBar.translucent = NO; //去除毛玻璃效果