Another part of the puzzle is that the window must be made key: [window makeKeyAndVisible]; of else the subviews are not automatically resized. I try to search for "the CommandManager detects conditions" and reach this exellent article.
The article includes other information, but the above part has been enough for me. I have put an example in this gist. It produces this result: The blue views have fixed heights.
Only authorized users can answer the question. Please sign in first, or register a free account. Not the answer you're looking for? Browse other questions tagged : ios. Related Answers. Top Answers Related To ios,cocoa-touch,autolayout,bounds,layoutsubviews. The system calls this method whenever it needs to recalculate the frames of views, so you should override it when you want to set frames and specify positioning and sizing. However, you should never call this explicitly when your view hierarchy requires a layout refresh.
Instead, there are multiple mechanisms you can use to trigger a layoutSubviews call at different points during the run loop that are much less expensive than calling layoutSubviews itself. When layoutSubviews completes, a call to viewDidLayoutSubviews is triggered in the view controller that owns the view. This is the only way you will avoid using stale layout and positioning variables for other computations. There are multiple events that automatically mark a view as having changed its layout, so that layoutSubviews will be called at the next opportunity without the developer doing this manually.
However, there are ways to trigger layoutSubviews directly as well. The least expensive way to trigger a layoutSubviews call is calling setNeedsLayout on your view.
Instead, the views will update on the next update cycle, when the system calls layoutSubviews on those views and triggers subsequent layoutSubviews calls on all their subviews.
There should be no user impact from the delay because, even though there is an arbitrary time interval between when setNeedsLayout returns and when views are redrawn and laid out, it should never be long enough to cause any lag in the application.
Instead of queueing layoutSubviews to run on the next update cycle, however, the system will call layoutSubviews immediately if the view needs a layout update. If you call layoutIfNeeded after calling setNeedsLayout or after one of the automatic refresh triggers described above, layoutSubviews will be called on the view.
However, if you call layoutIfNeeded and no action has indicated to the system that the view needs to be refreshed, layoutSubviews will not be called. If you call layoutIfNeeded on a view twice during the same run loop without updating its layout in between, the second call will not trigger a layoutSubviews call. Using layoutIfNeeded , laying out and redrawing subviews will happen right away and will have completed before this method returns except in the case where there are in flight animations , unlike setNeedsLayout.
This method is useful if you need to rely on the new layout and cannot wait until views are updated on the next update cycle. However, unless this is the case, you should call setNeedsLayout instead and wait for the next update cycle so that you only update views once per run loop. This method is especially useful when animating changes to constraints. You should call layoutIfNeeded before the start of an animation block to ensure all layout updates are propagated before the start of the animation.
Configure your new constraints, then inside the animation block, call layoutIfNeeded again to animate to the new state. Step to reproduce: 1. Subclass a UITextView 2.
Set some text 3. Set font or textColor in layoutSubviews method 4. Asked by lanvsblue. Copy to clipboard Share this post. Copied to Clipboard. Add a comment. Active Oldest Votes. Derek Lee 2, 3 3 gold badges 25 25 silver badges 32 32 bronze badges. BadPirate BadPirate 25k 10 10 gold badges 86 86 silver badges bronze badges.
Great answer. I have always wondered about layoutSubviews. Does initWithFrame: cause layoutSubviews to be called? Robert - I was using initWithFrame BadPirate: yes. According to my experiments, if you resize view1. This call does not propagate indefinitely to the superviews, calling it on view1. Just moving without changing it's size does not call layoutSubviews on any of them.
View Did load gets called after the UIView is init'd. Based on my experiment, the second rule may be not accurate: when I add view1. That is, not all the subviews of the target view are called layoutSubviews method. Show 10 more comments. I found that layoutSubviews: will be called on a view if and only if: Its own bounds not frame changed. The bounds of one of its direct subviews changed. A subview is added to the view or removed from the view.
Some relevant details: The bounds are considered changed only if the new value is different, including a different origin. Note specifically that is why layoutSubviews: is called whenever a UIScrollView scrolls, as it performs the scrolling by changing its bounds' origin. Changing the frame will only change the bounds if the size has changed, as this is the only thing propagated to the bounds property. A change in bounds of a view that is not yet in a view hierarchy will result in a call to layoutSubviews: when the view is eventually added to a view hierarchy.
Each iteration of the run loop, for all views in the view hierarchy , this flag is checked. For each view where the flag is found raised, layoutSubviews: is called on it and the flag is reset.
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