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Why viewdidlayoutsubviews call multiple times?

Posted by: admin November 30, 2017 Leave a comment

Questions:

I’m developing iOS Universal App on Swift,using auto layout and support only portrait.

I found UIViewController#viewdidlayoutsubviews called multiple times. Instead, viewDidLoad ONLY call once on starting up MyApp’s UIViewController.

Why viewdidlayoutsubviews call multiple times? Constraints on each UIView(UIButtons,UITextFields etc..) will perform in order?

Any Information will be appreciated.

Answers:

LoadView is only called one: 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.

See this link for more information. It uses Objective-C, but the information still holds.

Questions:
Answers:

The best thing to do and this has served me well – is to get in to the habit of adding a log or print statement to methods of which you are unsure

I use this ->
print(“Hello From (NSStringFromSelector(#function))”)

or this if inside a View Subclass
Swift.print(“Hello From (NSStringFromSelector(#function))”)

It will print the method when it is being called.

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