viewWillAppear 用于子视图

问题描述

我有带有多个 UIVIew 子视图的 UIScrollView.当每个 UIView 出现在 UIScrollView 的可见部分时，我想更新它们显示的数据.

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?我尝试了 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

你必须自己做计算.在滚动视图委托中实现 scrollViewDidScroll: 并手动计算哪些视图可见(例如，通过检查 CGRectIntersectsRect(scrollView.bounds, subview.frame) 是否返回 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.