UIWindow正在重置我的子视图

Question

I have two view controllers, one of them is a subview of the other. Both views are loaded up via nibs. The sub view controller has it position set in viewDidLoad of the parent view controller. When the parent view controller is set as the root view controller to the UIWindow, it resets the position of the sub view controller's view back to {0.0, 0.0} .

I know it is the window because I decided to observe the frame of the sub view controller's view and added a breakpoint ( the observer is the parent view controller ). The stack trace reports back with:

#0  0x000d34e0 in -[ParentViewController observeValueForKeyPath:ofObject:change:context:]
#1  0x32866eb0 in NSKeyValueNotifyObserver ()
#2  0x32866b0a in NSKeyValueDidChange ()
#3  0x32840eca in -[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:] ()
#4  0x39b87d9e in -[UIViewController viewDidMoveToWindow:shouldAppearOrDisappear:] ()
#5  0x39b4075e in -[UIView(Internal) _didMoveFromWindow:toWindow:] ()
#6  0x39b405be in -[UIView(Internal) _didMoveFromWindow:toWindow:] ()
#7  0x39b3ae4a in -[UIView(Hierarchy) _postMovedFromSuperview:] ()
#8  0x39b227dc in -[UIView(Internal) _addSubview:positioned:relativeTo:] ()
#9  0x39b222c2 in -[UIView(Hierarchy) addSubview:] ()
#10 0x39b7fe42 in -[UIWindow addRootViewControllerViewIfPossible] ()
#11 0x39b7bae4 in -[UIWindow _setHidden:forced:] ()

If I'm not meant to set the position in viewDidLoad where am I meant to set it?

Update: I thought it was just the position being changed, but through the same path, the dimension are being set. In the nib, it is set at landscape dimensions, but the frame is being set to portrait dimension at {0.0, 0.0} .

Answer 1

I would suggest doing it in viewWillAppear or viewDidAppear . When viewDidLoad is called, the view has only been loaded into the memory and has not been drawn to the screen yet which causes such problems.

Answer 2

Trying some different search keywords, I came across a couple of links that did prove very useful:

• View Frames change after being loaded
• UIView has portrait dimensions while in landscape?

The first goes into further detail of what Numan Tariq was saying and the last explains what is my problem.

The issue is that the auto resizing masks were not set. In the Interface Builder, sometimes the view has flexible width and height and locked to all margins, and sometimes it has just the left and top margins locked. For the way I am using it, I need the view to have the first. It now works and shows up the correct size and, thanks to Numan Tarig ;), position.