在UIScrollView中更改Alpha [英] Changing the alpha inside UIScrollView

问题描述

我试图实现使文本淡入淡出的效果，以显示这篇文章的UIScrollView中有更多数据： UIScrollView，通过滚动文本显示更多数据

I was trying to achieve the effect of having my text fade in and out to show there is more data in the UIScrollView in this post: UIScrollView, showing that there is more data by fading out text

我的背景不是简单的黑白背景，我无法使CAGradientLayer看起来正确，并且我无法使其匹配并使其看起来像文本正在褪色。因此，我想尝试在UIScrollView中设置alpha属性，或在UIScrollView中设置UILabel的alpha属性。但是，它会更改所有文本的字母。有没有办法只对一部分文本或一部分滚动视图做到这一点？谢谢！

I could not get the CAGradientLayer to look right since my background isn't a simple black and white background and I couldn't get it to match and make it look like the text is fading. So I thought I'd try setting the alpha property inside the UIScrollView, or the UILabel's alpha inside the UIScrollView. However, it changes all the text's alpha. Is there a way to do it for only a portion of the text, or a portion of the scrollView? Thanks!

推荐答案

有几种方法，其中至少有两种是相当容易的：

There are several ways, at least two of which are reasonably easy:

1. 创建带有羽化边缘的背景副本。


2. 在适当的视图上设置 view.layer.maskLayer （一个UIView包含滚动视图应该可以正常工作）（例如适当设置了content / contentsScale / contentsCenter的CALayer）。更麻烦的是，由于CALayer不会自动调整自身大小（因此，包装视图必须在-setFrame：/-setBounds：/-layoutSubviews中执行必要的操作）。您需要 #include< QuartzCore / CALayer.h> 。

1. Create a copy of your background with "feathered" edges. Stick this in a view on top of the scroll view.
2. Set view.layer.maskLayer on an appropriate view (a UIView containing the scroll view should work) to something suitable (e.g. a CALayer with contents/contentsScale/contentsCenter set appropriately). More of a pain, since CALayer does not autosize itself (so your wrapper view will have to do the necessary things in -setFrame:/-setBounds:/-layoutSubviews). You'll need to #include <QuartzCore/CALayer.h>.

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