iphone – 向单元格添加阴影会导致延迟滚动

概述所以我有一个有阴影的UIView： [containerFrame.layer setShadowOffset:CGSizeMake(0, 1)];[containerFrame.layer setShadowRadius:4.0];[containerFrame.layer setShadowColor:[UIColor colorWithRed:34/255.f green:25/255. 所以我有一个有阴影的UIVIEw：

[containerFrame.layer setShadowOffset:CGSizeMake(0,1)];[containerFrame.layer setShadowRadius:4.0];[containerFrame.layer setShadowcolor:[UIcolor colorWithRed:34/255.f green:25/255.f blue:25/255.f Alpha:1.0].CGcolor];[containerFrame.layer setShadowOpacity:0.4];

有了这个,我的滚动FPS下降到20-30.移除阴影然后繁荣,我的FPS回到60并且滚动像黄油一样光滑.现在的问题是我需要在这个盒子/容器视图周围有一个阴影效果.如何在不降低滚动速度的情况下实现这一目标？

解决方法 尝试设置阴影路径：

[containerFrame.layer setShadowOffset:CGSizeMake(0,1)];[containerFrame.layer setShadowRadius:4.0];[containerFrame.layer setShadowcolor:[UIcolor colorWithRed:34/255.f green:25/255.f blue:25/255.f Alpha:1.0].CGcolor];[containerFrame.layer setShadowOpacity:0.4];// New line[containerFrame.layer setShadowPath:[UIBezIErPath bezIErPathWithRect:containerFrame.bounds].CGPath];

If you have to animate this vIEw (and especially if it’s part of a
UItableVIEwCell) you will probably notice stutters in the animation.
This is because calculating the drop shadow for your vIEw requires
Core Animation to do an offscreen rendering pass to determine the
exact shape of your vIEw in order to figure out how to render its drop
shadow. (Remember,your vIEw Could be any complex shape,possibly
even with holes in it.)

从On the importance of setting shadowPath起.

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