我的 iPhone 应用程序从后台打开并选择 Tab atIndex:0 后崩溃
我实在想不通这个问题。当我单击链接从应用程序中打开 Safari、浏览网页，然后返回到我的应用程序时，我可以在 UITabBar 中打开并浏览两个 tabBarItems。但是，当我尝试选择一个 atIndex: 0 时，我得到一个 EXEC_BAD_ACCESS 和以下内容:(。任何人都可以帮我弄清楚如何避免这种情况发生吗？我目前没有在 will 或 didEnterBackground 或 Foreground None 中执行的任何代码，因此问题一定出在 中。 UIViewController 用于第一个选项卡（哦，我不知道为什么它要添加一个子视图。有什么想法吗？）。
Thread 0 Crashed: Dispatch queue: com.apple.main-thread
0 libobjc.A.dylib 0x0109ba63 objc_msgSend + 23
1 UIKit 0x0031f3df -[UIView(Internal) _didMoveFromWindow:toWindow:] + 966
2 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
3 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
4 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
5 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
6 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
7 UIKit 0x0031dfc4 -[UIView(Hierarchy) _postMovedFromSuperview:] + 166
8 UIKit 0x00316dfc -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1080
9 UIKit 0x0031514f -[UIView(Hierarchy) addSubview:] + 57
10 UIKit 0x003725ac -[UITransitionView transition:fromView:toView:] + 563
11 UIKit 0x00371955 -[UITransitionView transition:toView:] + 129
12 UIKit 0x003a6383 -[UITabBarController transitionFromViewController:toViewController:transition:shouldSetSelected:] + 459
13 UIKit 0x003a4d86 -[UITabBarController transitionFromViewController:toViewController:] + 64
14 UIKit 0x003a6b7e -[UITabBarController _setSelectedViewController:] + 263
15 UIKit 0x003a69ed -[UITabBarController _tabBarItemClicked:] + 352`
I really can't figure this out. When I click a link to open Safari from within my app, browse through the webpage, then return to my app, I can open and browse two tabBarItems in my UITabBar. But, when I try to select the one atIndex: 0, I get an EXEC_BAD_ACCESS and the following :(. Can anyone help me figure out how to make this not happen? I currently don't have any code that executes in will or didEnterBackground or Foreground. None. So the problem must be in the UIViewController for the first tab. (Oh and I don't know why it's adding a subview. Related?). Thoughts?
Thread 0 Crashed: Dispatch queue: com.apple.main-thread
0 libobjc.A.dylib 0x0109ba63 objc_msgSend + 23
1 UIKit 0x0031f3df -[UIView(Internal) _didMoveFromWindow:toWindow:] + 966
2 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
3 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
4 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
5 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
6 UIKit 0x0031f1b0 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 407
7 UIKit 0x0031dfc4 -[UIView(Hierarchy) _postMovedFromSuperview:] + 166
8 UIKit 0x00316dfc -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1080
9 UIKit 0x0031514f -[UIView(Hierarchy) addSubview:] + 57
10 UIKit 0x003725ac -[UITransitionView transition:fromView:toView:] + 563
11 UIKit 0x00371955 -[UITransitionView transition:toView:] + 129
12 UIKit 0x003a6383 -[UITabBarController transitionFromViewController:toViewController:transition:shouldSetSelected:] + 459
13 UIKit 0x003a4d86 -[UITabBarController transitionFromViewController:toViewController:] + 64
14 UIKit 0x003a6b7e -[UITabBarController _setSelectedViewController:] + 263
15 UIKit 0x003a69ed -[UITabBarController _tabBarItemClicked:] + 352`
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BAD_ACCESS 意味着您可能正在访问指向已释放内存的内容。在您描述的情况下，您的视图很可能由于内存不足警告而被卸载 - 特别是那些不可见的视图。如果您没有为此卸载做好准备，那么当视图重新加载时，通常会发生不好的事情。确保您在视图控制器中正确处理 viewDidUnload 方法和倒数 viewDidLoad 。
The BAD_ACCESS means you are likely accessing something that points to memory that has been released. In the situation you describe, it's very possible that your views are unloading due to a low memory warning - particularly ones that aren't visible. If you aren't prepared for this unloading, when the view reloads, bad things usually happen. Make sure you are appropriately handling your viewDidUnload method and the reciprocal viewDidLoad in your view controllers.