iOS：setFrame不再使用viewDidLoad或viewWillAppear

Question

I prefer to disable autoresizesSubviews and to use setFrame to place all of my subviews. As of iOS 6, things seem to have changed a lot. When I call setFrame on a view in viewDidLoad , there is no effect. I tried it from viewWillAppear ; same thing.

A setFrame call will work in willAnimateRotationToInterfaceOrientation , but that is not called initially like it was in iOS 5.

Can someone clarify please where I am expected to layout my views from?

Answer 1

I guess you want to layout your views from UIViewController. Have you tried performing your layout tasks in viewDidLayoutSubviews :

- (void)viewDidLayoutSubviews

According to Apple's documentation:

Your view controller can override this method to make changes after the view lays out its subviews.

Since your view itself does not do layout its subviews (you do not use autosize, autolayout or layoutSubViews:) you can do the layout tasks in this method.

Nevertheless, the elegant way would be to use a custom parent UIView and perform all the layout there, overriding UIView's layoutSubViews: (unless you add/removes views dinamically). Quote from Apple's documentation on "How View Controllers Participate in the View Layout Process" :

Ideally, the views themselves perform all of the necessary work to reposition themselves, without requiring the view controller to participate in the process at all. However, if the view controller adds and removes views dynamically, a static layout in Interface Builder may not be possible. In this case, the view controller is a good place to control the process, because often the views themselves only have a limited picture of the other views in the scene.

Answer 2

You can use setFrame in viewDidLoad if you uncheck the Autolayout option in Interface Builder. If you need to use auto layout, You need to perform your layout tasks in viewDidLayoutSubviews: .

Answer 3

Regarding "Asking the views to lay themselves out doesn't make sense to me. Views don't have authority to say where they should go. That's the role of the controller, isn't it?". I think the answer is often negative. It's the parent view (not view controller) which usually plays the role of laying out it's own subviews. It does so by utilizing autoresizingMask or autolayout (iOS 6 only). Or You can make layout programmatically by overriding -layoutSubviews method of the parent view.

Sure, like Imre mentioned, controller can participate in the layout process as well by overriding - (void)viewDidLayoutSubviews . I often use this approach when I don't want to subclass the top level view of the view controller for keep things simple.

Finally, I found this post super useful. Even with some minor errors, the post provides a big picture of view layout process.