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I am optimizing a transition that seems to be slow on my device. I am pushing one UIViewController from another when a UITableView's row is selected. There is a noticeable pause after row selection and before the new view is pushed.
Some logging indicates that all of my code is reasonably quick, from row selection until the pushed controller's viewWillAppear. But then the time between viewWillAppear and viewDidAppear is logged at around 0.7 seconds.
The transition itself (I believe) should only take 0.3 seconds. What could be accounting for the remainder?
I am testing on an iPhone 4, so I'm not expecting the snappiest performance. But I should be able to match the same performance of other similar apps on the same device, no?
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viewWillAppear(_:)Always called after viewDidLoad (for obvious reasons, if you think about it), and just before the view appears on the screen to the user, viewWillAppear is called.
The difference between viewDidAppear and viewDidLoad is that viewDidAppear is called every time you land on the screen while viewDidLoad is only called once which is when the app loads.
viewDidAppear is called once you see the loaded view on screen. It is called after view appeared.
If both these methods are called, what's the difference between the two? viewDidLoad() is only called once, when the view is loaded from a . storyboard file. viewWillAppear(_:) is called every time the view appears.
I had a similar question a few weeks ago, and I wrote a blog post about what I found:
http://bradbambara.wordpress.com/2014/07/31/object-life-cycle-uiviewcontroller/
The TL;DR version is that iOS will:
...so my guess is the delay could be caused by an especially long transition, or if you're doing any performance-intensive work in your layout code.
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The transition itself (I believe) should only take 0.3 seconds. What could be accounting for the remainder?
Resources are usually consumed in the following methods: drawRect:, layoutSubviews, viewDidLoad, viewWillAppear:. Also, loading from NIB may require quite much time.
After viewWillAppear:, iOS will make a snapshot of the new (and probably current) view to perform smooth animation between two screens. So make sure that drawing and layout code for both controller views is fast enough.
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