viewWillAppear用于子视图 [英] viewWillAppear for subviews

问题描述

我有多个UIVIew子视图的UIScrollView。我想更新每个UIView出现在UIScrollView可见部分时显示的数据。

I have UIScrollView with multiple UIVIew subviews. I would like to update the data that is displayed by each UIView when they appear in the visible portion of the UIScrollView.

触发的回调是什么？我试过了viewWillAppear，但它似乎没有被调用。

What is the callback that gets triggered? I tried viewWillAppear, but it does not seem to get called.

谢谢。 ：）

推荐答案

您必须自己进行计算。在滚动视图委托中实现 scrollViewDidScroll：并手动计算哪些视图是可见的（例如，通过检查 CGRectIntersectsRect（scrollView.bounds，subview.frame）返回true。

You have to do the calculation yourself. Implement scrollViewDidScroll: in your scroll view delegate and calculate manually which views are visible (e.g. by checking if CGRectIntersectsRect(scrollView.bounds, subview.frame) returns true.

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