在 UICollectionViewFlowLayout 使其布局无效后重绘单元格 [英] Redraw cells after UICollectionViewFlowLayout invalidates its layout

问题描述

当您使 UICollectionViewFlowLayout 上的布局无效时，它会为您的每个单元格创建一堆新的布局属性；但是，它不会告诉您的单元格重新绘制，这会导致任何图层绘图中的扭曲.

When you invalidate layout on a UICollectionViewFlowLayout it creates a bunch of new layout attributes for each of your cells; it doesn't tell your cells to redraw however, which causes distortions in any Layer drawings.

我不想告诉我的集合重新加载它的数据，因为这会删除你在流属性之间的任何好的过渡:例如，我有一个网格布局过渡到一个覆盖流.

I don't want to tell my collection to reload its data because this removes any nice transitions you have between flow attributes : I have a grid layout transitioning into a coverflow for example.

我需要一种方法让 UICollectionViewController 类告诉单元格在获得布局属性后调用它们的 [setNeedsDisplay] 方法.

I need a way for the UICollectionViewController class to tell the cells to call their [setNeedsDisplay] method after being given the layout attributes.

推荐答案

当您的单元格改变大小时，由他们来处理(拉伸与重绘).这是由 UIView contentMode 属性控制的；尝试将其设置为 UIViewContentModeRedraw 以导致调整大小使您的视图内容无效，例如 setNeedsDisplay: 会.

When your cells change size, it's up to them how to handle that (stretching vs redrawing). This is controlled by the UIView contentMode property; try setting it to UIViewContentModeRedraw to cause resizing to invalidate your views contents like setNeedsDisplay: would.

如果您直接使用 CALayer 作为单元格的子层，您可以将它们的 needsDisplayOnBoundsChange 设置为 YES 以获得相同的效果.

If you're using CALayers directly as sub-layers of your cell, you can set their needsDisplayOnBoundsChange to YES in order to get the same effect.

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