ios setNeedsLayout 和 setNeedsDisplay
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setNeedsLayout and setNeedsDisplay
提问by DuckDucking
What is the real difference between UIViewmethods setNeedsLayoutand setNeedsDisplay?
UIView方法setNeedsLayout和之间的真正区别是什么setNeedsDisplay？
As usual documentation is foggy about this.
像往常一样，文档对此很模糊。
回答by Joris Kluivers
Actually the documentation is pretty clear about this:
实际上，文档对此非常清楚：
setNeedsLayoutwill layout subviews
Call this method on your application's main thread when you want to adjust the layout of a view's subviews.
setNeedsDisplaywill call for a redraw of your view (
drawRect:, etc).You can use this method or the setNeedsDisplayInRect: to notify the system that your view's contents need to be redrawn.
setNeedsLayout将布局子视图
当您想要调整视图子视图的布局时，请在应用程序的主线程上调用此方法。
setNeedsDisplay将要求重绘您的视图（
drawRect:等）。您可以使用此方法或 setNeedsDisplayInRect: 通知系统您的视图内容需要重绘。
