Ios – When is layoutSubviews called

autolayoutboundscocoa-touchioslayoutsubviews

I have a custom view that's not getting layoutSubview messages during animation.

I have a view that fills the screen. It has a custom subview at the bottom of the screen that correctly resizes in Interface Builder if I change the height of the nav bar. layoutSubviews is called when the view is created, but never again. My subviews are correctly laid out. If I toggle the in-call status bar off, the subview's layoutSubviews is not called at all, even though the main view does animate its resize.

Under what circumstances is layoutSubviews actually called?

I have autoresizesSubviews set to NO for my custom view. And in Interface Builder I have the top and bottom struts and the vertical arrow set.

Another part of the puzzle is that the window must be made key:

[window makeKeyAndVisible];

of else the subviews are not automatically resized.

Best Answer

I had a similar question, but wasn't satisfied with the answer (or any I could find on the net), so I tried it in practice and here is what I got:

init does not cause layoutSubviews to be called (duh)
addSubview: causes layoutSubviews to be called on the view being added, the view it’s being added to (target view), and all the subviews of the target
view setFrame intelligently calls layoutSubviews on the view having its frame set only if the size parameter of the frame is different
scrolling a UIScrollView causes layoutSubviews to be called on the scrollView, and its superview
rotating a device only calls layoutSubview on the parent view (the responding viewControllers primary view)
Resizing a view will call layoutSubviews on its superview (Important: views with an intrinsic content size will re-size if the content that determines their size changes; for example, updating the text on a UILabel will cause the intrinsic content size to be updated and thus call layoutSubviews on its superview)

My results - http://blog.logichigh.com/2011/03/16/when-does-layoutsubviews-get-called/

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Ios – Event handling for iOS – how hitTest:withEvent: and pointInside:withEvent: are related

I think you are confusing subclassing with the view hierarchy. What the doc says is as follows. Say you have this view hierarchy. By hierarchy I'm not talking about class hierarchy, but views within views hierarchy, as follows:

+----------------------------+
|A                           |
|+--------+   +------------+ |
||B       |   |C           | |
||        |   |+----------+| |
|+--------+   ||D         || |
|             |+----------+| |
|             +------------+ |
+----------------------------+

Say you put your finger inside D. Here's what will happen:

hitTest:withEvent: is called on A, the top-most view of the view hierarchy.
pointInside:withEvent: is called recursively on each view.
1. pointInside:withEvent: is called on A, and returns YES
2. pointInside:withEvent: is called on B, and returns NO
3. pointInside:withEvent: is called on C, and returns YES
4. pointInside:withEvent: is called on D, and returns YES
On the views that returned YES, it will look down on the hierarchy to see the subview where the touch took place. In this case, from A, C and D, it will be D.
D will be the hit-test view

Ios – How to bring a subview to the front when you tap it

bringSubviewToFront should work, just make sure you're using it correctly. The usage is.

[parentView bringSubviewToFront:childView];

Best Answer

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Ios – Event handling for iOS – how hitTest:withEvent: and pointInside:withEvent: are related

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