为什么在设置UIWindow的rootViewController属性时viewDidLoad被调用了两次？ [英] Why is viewDidLoad called twice when the rootViewController property of UIWindow is set?
问题描述
已经有几个类似的问题，但它与我的情况并不完全相同。只需启动一个新的基于视图的项目，使用NSLog语句添加 viewDidLoad 和 awakeFromNib 并在<$ c中执行以下更改$ c> MainWindow.xib ：
There were already a couple of similar questions, but it wasn’t exactly the same as in my case. Just start a new view based project, add viewDidLoad and awakeFromNib with NSLog statements and do the following changes in MainWindow.xib:
- 删除应用程序代理中的视图控制器连接。
- 连接
UIWindow的rootViewController委托给App View Controller实例。
- Remove the view controller connection in the application delegate.
- Connect
UIWindow’srootViewControllerdelegate to the App View Controller instance.
第一次通话时的堆栈跟踪：
The stack trace from the first call:
#0 0x000025c0 in -[foozaViewController viewDidLoad] at /Users/rafael/Downloads/fooza/fooza/foozaViewController.m:38
#1 0x000cd089 in -[UIViewController view] ()
#2 0x00040d42 in -[UIWindow addRootViewControllerViewIfPossible] ()
#3 0x0079d5e5 in -[NSObject(NSKeyValueCoding) setValue:forKey:] ()
#4 0x00050ff6 in -[UIView(CALayerDelegate) setValue:forKey:] ()
#5 0x0021930c in -[UIRuntimeOutletConnection connect] ()
#6 0x00d418cf in -[NSArray makeObjectsPerformSelector:] ()
#7 0x00217d23 in -[UINib instantiateWithOwner:options:] ()
#8 0x00219ab7 in -[NSBundle(UINSBundleAdditions) loadNibNamed:owner:options:] ()
#9 0x0001f17a in -[UIApplication _loadMainNibFile] ()
#10 0x0001fcf4 in -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] ()
#11 0x0002a617 in -[UIApplication handleEvent:withNewEvent:] ()
#12 0x00022abf in -[UIApplication sendEvent:] ()
#13 0x00027f2e in _UIApplicationHandleEvent ()
#14 0x01004992 in PurpleEventCallback ()
#15 0x00dac944 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ ()
#16 0x00d0ccf7 in __CFRunLoopDoSource1 ()
#17 0x00d09f83 in __CFRunLoopRun ()
#18 0x00d09840 in CFRunLoopRunSpecific ()
#19 0x00d09761 in CFRunLoopRunInMode ()
#20 0x0001f7d2 in -[UIApplication _run] ()
#21 0x0002bc93 in UIApplicationMain ()
#22 0x000020d9 in main ()
这是第二次调用的跟踪：
And here’s the trace from the second call:
#0 0x000025c0 in -[foozaViewController viewDidLoad] at /Users/rafael/Downloads/fooza/fooza/foozaViewController.m:38
#1 0x00002555 in -[foozaViewController awakeFromNib] ()
#2 0x00217f26 in -[UINib instantiateWithOwner:options:] ()
#3 0x00219ab7 in -[NSBundle(UINSBundleAdditions) loadNibNamed:owner:options:] ()
#4 0x0001f17a in -[UIApplication _loadMainNibFile] ()
#5 0x0001fcf4 in -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] ()
#6 0x0002a617 in -[UIApplication handleEvent:withNewEvent:] ()
#7 0x00022abf in -[UIApplication sendEvent:] ()
#8 0x00027f2e in _UIApplicationHandleEvent ()
#9 0x01004992 in PurpleEventCallback ()
#10 0x00dac944 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ ()
#11 0x00d0ccf7 in __CFRunLoopDoSource1 ()
#12 0x00d09f83 in __CFRunLoopRun ()
#13 0x00d09840 in CFRunLoopRunSpecific ()
#14 0x00d09761 in CFRunLoopRunInMode ()
#15 0x0001f7d2 in -[UIApplication _run] ()
#16 0x0002bc93 in UIApplicationMain ()
#17 0x000020d9 in main ()
<这是理想的行为还是错误？我们是否仍然应该使用更传统的
方式将插座连接到
应用程序委托中的根视图控制器，以保持理智的 viewDidLoad / viewDidUnload 比率
或者我们应该忽略Apple的规则而不要在 awakeFromNib 中调用super并使用新的 rootViewController 属性 UIWindow ？
Is this desired behavior or a bug? Should we still use the more traditional
way of connecting an outlet to the root view controller in the
application delegate to maintain a sane viewDidLoad/viewDidUnload ratio
or should we ignore Apple’s rules and do not call super in awakeFromNib and use the new rootViewController property of UIWindow?
推荐答案
它看起来像一个bug，因为它只能在Xcode 4中重现。我会提交一个bug。
It looks like a bug, because it’s only reproducible in Xcode 4. I will file a bug.
另见 http://shurl.at/5u （Apple开发者论坛）
See also http://shurl.at/5u (Apple Developer Forums)
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