ios开发UIView自适应问题

http://blog.csdn.net/ouyangtianhan/article/details/17282209

我的UIViewController的Xib里面的View是 3.5寸的即（320*480）的。

在设置自适应自动伸长以后，经常会在ViewDidLoad方法里面初始化一些界面，这时候使用主self.view.frame时，发现frame和xib里面的尺寸是一样的，并没有自适应伸长，结果很多subview错位了，上网查了下，在stackoverflow上发现一段说明：

　

The frame is not guaranteed to be the same in viewDidLoad as it will be when the view is eventually displayed. UIKit adjusts the frame of your view controller's view prior to
displaying it, based on the context in which will appear. The size is determined based on interface orientation and the dimensions of any visible navigation bar, tab bar, toolbar, or status bar (which itself has a height that can change, e.g. when you're
on a phone call).

It helps to understand what happens when a view controller's view is loaded and displayed:

Something accesses your view controller's 

view

 property
for the first time. This may occur in your own code, or in UIKit in response to a user action like selecting a tab.

UIKit lazy-loads your view controller's view by calling 

loadView

 if
it's defined, or by loading the view from the NIB that was specified in 

initWithNibName:bundle:

.
If neither exists, UIKit just loads an empty view.

UIKit calls 

viewDidLoad

 once
the view and its subviews have been fully loaded. At this point the view's frame will be whatever it was
set to in the NIB, or in 

loadView

.

Something calls for UIKit to display your view controller's view. Again, this may be a user action like tapping on a tab, or an explicit method call in your code like 

pushViewController:animated:

 or

presentModalViewController:animated:

.

UIKit resizes the view based on the context in which it will be presented, as described above.

UIKit calls 

viewWillAppear:

. The
frame should now be the size that will be displayed.

UIKit displays the view, with or without animations.

UIKit calls 

viewDidAppear:

.

As you can see, if you need to know the size of your view's frame before it gets presented,

viewWillAppear:

 is
your one and only opportunity. Just remember that this size may change after the view appears for various reasons, including rotation events or changes in status bar height. For this reason, it's important to give every subview an appropriate autoresizingMask,
to ensure that the layout can adjust itself properly for any change in bounds.

If you wish to build your view hierarchy manually, the recommended place to do so is in loadView. Since you construct the view yourself in this method, you can initialize its frame to whatever you'd like. The size you choose doesn't matter much, since UIKit
is likely to change it on you anyway. Just make sure you set your autoresizingMasks appropriately.
其实代码是没错的，不管是在xib里面设置自适应，还是在ViewDidLoad方法里卖弄设置，得到的self.view.frame始终是和xib里面的尺寸是一样的，这时你就郁闷了，因为很多subView的尺寸要根据self.view的尺寸来设置。

所以对subView的一些适应性设置，不能在Viewdidload里面，而是需要在viewWillAppear和viewDidAppear里面完成，在这两个方法里面self.view.frame是自适应之后的值。

自己认为最好的方式，还是对subview设置好合适autoresizingMasks。