UIViewController returns invalid frame?

ios, landscape, uiviewcontroller

Solution

There are a couple of things that you don't understand.

First, the system sends you `viewDidLoad` immediately after loading your nib. It hasn't even added the view to the view hierarchy yet. So it hasn't resized your view based on the device's rotation either.

Second, a view's frame is in its superview's coordinate space. If this is your root view, its superview will be the `UIWindow` (once the system actually adds your view to the view hierarchy). The `UIWindow` handles rotation by setting the transform of its subview. This mean that the view's frame will not necessarily be what you expect.

Here's the view hierarchy in portrait orientation:

(lldb) po [[UIApp keyWindow] recursiveDescription]
(id) $1 = 0x09532dc0 <UIWindow: 0x9632900; frame = (0 0; 768 1024); layer = <UIWindowLayer: 0x96329f0>>
   | <UIView: 0x9634ee0; frame = (0 20; 768 1004); autoresize = W+H; layer = <CALayer: 0x9633b50>>

and here's the view hierarchy in landscape-left orientation:

(lldb) po [[UIApp keyWindow] recursiveDescription]
(id) $2 = 0x09635e70 <UIWindow: 0x9632900; frame = (0 0; 768 1024); layer = <UIWindowLayer: 0x96329f0>>
   | <UIView: 0x9634ee0; frame = (20 0; 748 1024); transform = [0, -1, 1, 0, 0, 0]; autoresize = W+H; layer = <CALayer: 0x9633b50>>

Notice that in landscape orientation, the frame size is 748 x 1024, not 1024 x 748.

What you probably want to look at, if this is your root view, is the view's bounds:

(lldb) p (CGRect)[0x9634ee0 bounds]
(CGRect) $3 = {
  (CGPoint) origin = {
    (CGFloat) x = 0
    (CGFloat) y = 0
  }
  (CGSize) size = {
    (CGFloat) width = 1024
    (CGFloat) height = 748
  }
}

Presumably you want to know when the view's transform, frame, and bounds get updated. If the interface is in a landscape orientation when your view controller loads its view, you will receive messages in this order:

{{0, 0}, {768, 1004}} viewDidLoad
{{0, 0}, {768, 1004}} shouldAutorotateToInterfaceOrientation:
{{0, 0}, {768, 1004}} shouldAutorotateToInterfaceOrientation:
{{0, 0}, {768, 1004}} viewWillAppear:
{{0, 0}, {768, 1004}} shouldAutorotateToInterfaceOrientation:
{{0, 0}, {768, 1004}} shouldAutorotateToInterfaceOrientation:
{{0, 0}, {768, 1004}} willRotateToInterfaceOrientation:duration:
{{0, 0}, {1024, 748}} viewWillLayoutSubviews
{{0, 0}, {1024, 748}} layoutSubviews
{{0, 0}, {1024, 748}} viewDidLayoutSubviews
{{0, 0}, {1024, 748}} willAnimateRotationToInterfaceOrientation:duration:
{{0, 0}, {1024, 748}} shouldAutorotateToInterfaceOrientation:
{{0, 0}, {1024, 748}} viewDidAppear:

You can see that your view's bounds change after you receive `willRotateToInterfaceOrientation:duration:` and before you receive `viewWillLayoutSubviews`.

The `viewWillLayoutSubviews` and `viewDidLayoutSubviews` methods are new to iOS 5.0.

The `layoutSubviews` message is sent to the view, not the view controller, so you will need to create a custom `UIView` subclass if you want to use it.

Problem

Original source