When is layoutSubviews called

Knowing once the layoutSubviews methodology will get referred to as is important for iOS builders. This technique performs a critical function successful the lifecycle of a UIView and dictates however your person interface parts are positioned and sized. Mastering its nuances tin beryllium the quality betwixt a creaseless, responsive UI and 1 plagued by show points oregon surprising format glitches. This article volition delve into the intricacies of layoutSubviews, offering applicable examples and champion practices to aid you harness its powerfulness efficaciously.

Triggers for layoutSubviews

layoutSubviews isn’t referred to as arbitrarily. Circumstantial occasions set off this technique, and knowing these triggers is indispensable for optimizing your UI updates. Any communal triggers see:

• Including a subview to a position.
• Altering the bounds of a position.
• Resizing a position, together with rotating the instrumentality.
• Calling setNeedsLayout connected a position.
• Calling layoutIfNeeded connected a position.

It’s crucial to line that merely altering a position’s framework doesn’t straight call layoutSubviews. Alternatively, it marks the position arsenic needing a structure replace, which volition set off layoutSubviews throughout the adjacent replace rhythm. This optimization helps forestall pointless format calculations.

layoutSubviews vs. drawRect

Frequently, layoutSubviews is confused with drawRect. Piece some woody with the ocular points of a position, they person chiseled roles. layoutSubviews offers solely with the positioning and sizing of subviews. drawRect, connected the another manus, is liable for drafting the contented of a position. Understanding the quality is important for businesslike UI improvement.

Deliberation of it this manner: layoutSubviews units the phase, figuring out wherever all histrion (subview) ought to base. drawRect past paints the surroundings and the actors themselves. They activity successful tandem, however their tasks are intelligibly separated.

Optimizing layoutSubviews for Show

Since layoutSubviews tin beryllium known as often, particularly throughout analyzable animations oregon interactions, optimizing its show is captious. Debar performing dense computations oregon creating fresh objects inside this methodology. If you demand to execute analyzable calculations, see caching the outcomes oregon performing them asynchronously.

Moreover, lone call setNeedsLayout oregon layoutIfNeeded once perfectly essential. Overusing these strategies tin pb to pointless format passes and contact show. Usage Devices to chart your app and place immoderate bottlenecks associated to layoutSubviews.

1. Chart your app utilizing Devices.
2. Place bottlenecks successful layoutSubviews.
3. Optimize calculations and entity instauration.
4. Usage setNeedsLayout and layoutIfNeeded judiciously.

Applicable Examples and Usage Circumstances

Fto’s see a existent-planet script: gathering a customized array position compartment. Inside the layoutSubviews methodology of your customized compartment, you would cipher and fit the frames of the compartment’s subviews (labels, pictures, and many others.) primarily based connected the compartment’s contented and width. This ensures that the components are appropriately positioned and sized once the compartment is displayed.

Different illustration is creating a customized position that dynamically adjusts its structure based mostly connected its contented. Wrong layoutSubviews, you would cipher the dimension and assumption of the subviews based mostly connected the contented’s dimensions, making certain a responsive and adaptive structure.

“Format is 1 of the about crucial points of iOS improvement. Mastering layoutSubviews is cardinal to gathering advanced-show and visually interesting apps.” - Adept iOS Developer.

For much elaborate accusation connected car format and constraints, mention to Pome’s Car Format Usher.

Often Requested Questions

Q: Once ought to I call setNeedsLayout?

A: Call setNeedsLayout once you privation to set off a format replace however don’t demand it to hap instantly. This methodology marks the position arsenic needing a format replace, which volition happen throughout the adjacent replace rhythm.

Q: What is the quality betwixt setNeedsLayout and layoutIfNeeded?

A: setNeedsLayout schedules a format replace for the adjacent replace rhythm. layoutIfNeeded, connected the another manus, forces an contiguous format replace if the position has been marked arsenic needing 1.

Leveraging a heavy knowing of layoutSubviews empowers builders to trade polished, advanced-show person interfaces. By knowing the triggers, optimizing for show, and using champion practices, you tin guarantee your iOS apps present a seamless and responsive person education. For additional aid connected optimizing your app’s UI, see our blanket usher. This usher delves into precocious strategies for UI optimization, together with asynchronous structure and customized format transitions. Research associated matters specified arsenic Car Structure, UI show champion practices, and position drafting cycles to additional heighten your iOS improvement expertise. Don’t hesitate to research sources similar Ray Wenderlich and objc.io for equal much successful-extent accusation and tutorials.

Question & Answer :
I person a customized position that’s not getting layoutSubview messages throughout animation.

I person a position that fills the surface. It has a customized subview astatine the bottommost of the surface that appropriately resizes successful Interface Builder if I alteration the tallness of the nav barroom. layoutSubviews is known as once the position is created, however ne\’er once more. My subviews are appropriately laid retired. If I toggle the successful-call position barroom disconnected, the subview’s layoutSubviews is not referred to as astatine each, equal although the chief position does animate its resize.

Nether what circumstances is layoutSubviews really known as?

I person autoresizesSubviews fit to Nary for my customized position. And successful Interface Builder I person the apical and bottommost struts and the vertical arrow fit.

Different portion of the puzzle is that the framework essential beryllium made cardinal:

[framework makeKeyAndVisible]; 

of other the subviews are not routinely resized.

I had a akin motion, however wasn’t happy with the reply (oregon immoderate I may discovery connected the nett), truthful I tried it successful pattern and present is what I bought:

• init does not origin layoutSubviews to beryllium referred to as (duh)
• addSubview: causes layoutSubviews to beryllium referred to as connected the position being added, the position it’s being added to (mark position), and each the subviews of the mark
• position setFrame intelligently calls layoutSubviews connected the position having its framework fit lone if the measurement parameter of the framework is antithetic
• scrolling a UIScrollView causes layoutSubviews to beryllium known as connected the scrollView, and its superview
• rotating a instrumentality lone calls layoutSubview connected the genitor position (the responding viewControllers capital position)
• Resizing a position volition call layoutSubviews connected its superview (Crucial: views with an intrinsic contented measurement volition re-dimension if the contented that determines their dimension adjustments; for illustration, updating the matter connected a UILabel volition origin the intrinsic contented measurement to beryllium up to date and frankincense call layoutSubviews connected its superview)

My outcomes - http://weblog.logichigh.com/2011/03/sixteen/once-does-layoutsubviews-acquire-known as/