Why does animating a subview cause its parent view's layoutSubviews method to be called?

Question

I'm doing UIView animation on individual subviews that have a number of sibling views that I don't want affected by the single-view animation. However layoutSubviews is being called on the containing superview when I do the animation, causing the other siblings to be rearranged as well.

(I should explain that I'm doing initial subview layout in the parent view's layoutSubviews method; I only want it to be called the first time I'm setting up the subviews, not when I'm animating them individually later on.)

Why is the parent view's layoutSubviews method being called when animating its subviews?

Answer 1

I can imagine "sorting a grid of icons", you'll just have to animate one icon and the rest works automatically.

On the other side: What autoresizing masks do you have set for the view you're animating? Perhaps it has to do with that. What type of UIView are you animating? Perhaps it changes shape and thus calls [self.superview setNeedsLayout] to tell the superview that it changed shape.

Other idea: Has your superview "autoresizedSubviews" set?

Answer 2

I've found that even setting transformations on the layers of a view can trigger the view's setLayoutSubviews. It took me by surprise too, but maybe just because I don't need the behavior right now. It might sometimes become handy, I guess…