View height problems (continued) - ios

Question

This is in continuation to the problem I had here(which is still unresolved): link
But this may help understand what is the problem.
I created just a simple test project ('Empty Application') and added a view controller with a XIB file (check box: 'With XIB file for user interface' selected). Code looks like this:
- (void)viewDidLoad
{
[super viewDidLoad];
NSLog(#"didLoad: %#",NSStringFromCGRect(self.view.bounds));
// Do any additional setup after loading the view from its nib.
}
-(void) viewDidAppear:(BOOL)animated
{
NSLog(#"didAppear: %#",NSStringFromCGRect(self.view.bounds));
}
This is the output:
2013-07-26 17:05:28.502 testtest[5926:c07] didLoad: {{0, 0}, {320, 548}}
2013-07-26 17:05:28.506 testtest[5926:c07] didAppear: {{0, 0}, {320, 460}}
How come they are different?
(ps. I am testing on 6.1 simulator)

Answer 1

When the viewDidLoad method is called, your view controller has only just been loaded from your storyboard or XIB, and so the view dimensions are equal to those that you have in the XIB (those looks like iPhone 5 height dimensions).
Later, when viewDidAppear: is called, the view has already appeared on the screen, so it has been resized appropriately to actually fit on the screen, so its dimensions may be different to those in your storyboard, and consequently different to those that are set when the view is loaded.
In your case, it looks like your storyboard or XIB file is set to iPhone 5 screen size (548 = 1136/2 - status bar), and you are testing in a pre-iPhone 5 simulator or device with a 480x320 point screen, so the view gets resized down to 460 points high to fit on the screen.

Answer 2

This could have perfect sense.
ViewDidLoad is called lazily when first access of controller.view, so by that time the frame is not set yet. This means that you can not rely on the frame/bounds sizes at this point because it will only contain a default value (although in many cases it will be correct).
In ViewDidAppear, the frame is usually set, although if your parent controller is setting any animation you could also have a temporal frame state instead of the final one, but it is not usual as by convention this method is called when the view is already displayed.
For example, if you are loading the view from an IB file, the frame you will get in the viewDidLoad is the one you have in the IB file, but maybe the final size for your view is smaller/bigger, and then you will get another one in your viewDidAppear.
Instead of that, you should create all your elements resizable (use Spring&Struts, AutoLayout or any other similar alternative) so they will be properly displayed when the frame is set.

Answer 3

When a ViewController presents its view, it normally shrinks that
view so that its frame does not overlap the device’s status bar.
So when you NSLog in viewDidLoad, the View i not yet loaded so ViewController has not shrinked the frame yet but in viewDidAppear , it has done the resizing.
There is a property in UIViewController
wantsFullScreenLayout
Setting this property to YES causes the view controller to size its
view so that it fills the entire screen, including the area under the
status bar. (Of course, for this to happen, the window hosting the
view controller must itself be sized to fill the entire screen,
including the area underneath the status bar.) You would typically set
this property to YES in cases where you have a translucent status bar
and want your view’s content to be visible behind that view.

Answer 4

As far as i know, ViewDidLoad will set the bounds for your application as defined, in the RootViewController/XIB-file for root view, or maybe the AppDelegate.
If you define the applications bounds there (not sure in which one of these), ViewDidLoad functions in the entire app, will initially, set the height according to that.
Once the View is loaded, and ready to 'appear', actual bounds may be requested.
Hence it is advised to request bounds/sizes in the ViewWillAppear/ViewDidAppear methods.

Answer 5

-viewDidLoad is called the first time viewController.view is called. It is called before the view is returned. This has a very important implication. In order for the view to be shown or sized, it needs to be added to the window or some other view.
How does this happen? It looks something like [window addSubview:viewController.view].
So, the fully loaded view is needed before it can be placed into the view hierarchy. This places limitations on self.view when used within -viewDidLoad.
self.view.superview and self.view.window will always be nil.
self.view is not yet sized to fit into self.view.superview.
With this understanding, you can see how self.view cannot know it's final size when -viewDidLoad is called.
UPDATE
If you need to apply a custom layout to a view's subviews, you may want to consider subclassing UIView and using -[UIView layoutSubviews].
Barring that, are you having trouble with -viewWillAppear: instead of -viewDidAppear:? -viewWillAppear: is called before the view is displayed, so you won't have odd visual effects when you resize the view.