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I'm developing iOS Universal App with Swift, using auto layout and support only portrait.
I found UIViewController.viewDidLayoutSubviews called multiple times. Instead, viewDidLoad is only called once on starting up MyApp's UIViewController.
Why is viewDidLayoutSubviews called multiple times? Will constraints on each UIView (UIButtons,UITextFields, etc..) be performed in order?
Any information will be appreciated.
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Ans : ViewDidLoad called once only when all views are loaded. viewDidLayoutSubviews : Apple gave a very good explanation on this by saying that it is called to notify the view controller that its view has just laid out its subviews.
viewDidLoad() is one of the initialization methods that is called on the initial view controller. viewDidLoad() is called before anything is shown to the user - and it is called only once.
Called to notify the view controller that its view has just laid out its subviews.
layoutIfNeeded()Lays out the subviews immediately, if layout updates are pending.
LoadView is only called once: when the view needs to be loaded.
LayoutSubviews, however, is called once per run loop on any view that has had setNeedsLayout or setNeedsDisplayInRect called on it - this includes whenever a subview has been added to the view, scrolling, resizing, etc.
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