当我从一个标签切换到另一个标签时，有时会发生奇怪的崩溃：
0 libobjc.A.dylib 0x3857e636 objc_msgSend + 22
1 UIKit 0x3024ca89 -[UIResponder(Internal) _canBecomeFirstResponder] + 21
2 UIKit 0x3024c7a3 -[UIResponder becomeFirstResponder] + 207
3 UIKit 0x3024caff -[UIView(Hierarchy) becomeFirstResponder] + 107
4 UIKit 0x302c946b -[UITextField becomeFirstResponder] + 47
5 UIKit 0x302ca345 -[UIView(Hierarchy) deferredBecomeFirstResponder] + 57
6 UIKit 0x301cd441 __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke + 165
7 Foundation 0x2e304d33 -[NSISEngine withBehaviors:performModifications:] + 211
8 UIKit 0x301cd291 -[UIView(Hierarchy) _postMovedFromSuperview:] + 297
9 UIKit 0x301da01d -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1413
10 UIKit 0x301d9a93 -[UIView(Hierarchy) addSubview:] + 31
11 UIKit 0x302bb563 -[UITransitionView transition:fromView:toView:removeFromView:] + 979
12 UIKit 0x302fb783 -[UITransitionView transition:fromView:toView:] + 31
13 UIKit 0x302fb759 -[UITransitionView transition:toView:] + 105
14 UIKit 0x302fa87b -[UITabBarController transitionFromViewController:toViewController:transition:shouldSetSelected:] + 1107
15 UIKit 0x302fa41f -[UITabBarController transitionFromViewController:toViewController:] + 39
16 UIKit 0x302fa2f7 -[UITabBarController _setSelectedViewController:] + 259
17 UIKit 0x303c45c9 -[UITabBarController _tabBarItemClicked:] + 273
18 UIKit 0x302036c7 -[UIApplication sendAction:to:from:forEvent:] + 91
19 UIKit 0x30203663 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 39
20 UIKit 0x303c447f -[UITabBar _sendAction:withEvent:] + 371
21 UIKit 0x302036c7 -[UIApplication sendAction:to:from:forEvent:] + 91
22 UIKit 0x30203663 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 39
23 UIKit 0x30203633 -[UIControl sendAction:to:forEvent:] + 47
24 UIKit 0x301eed7b -[UIControl _sendActionsForEvents:withEvent:] + 375
25 UIKit 0x303c41a7 -[UITabBar(Static) _buttonUp:] + 119
26 UIKit 0x302036c7 -[UIApplication sendAction:to:from:forEvent:] + 91
27 UIKit 0x30203663 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 39
28 UIKit 0x30203633 -[UIControl sendAction:to:forEvent:] + 47
29 UIKit 0x301eed7b -[UIControl _sendActionsForEvents:withEvent:] + 375
30 UIKit 0x3020307b -[UIControl touchesEnded:withEvent:] + 595
31 UIKit 0x30202d4d -[UIWindow _sendTouchesForEvent:] + 529
32 UIKit 0x301fdca7 -[UIWindow sendEvent:] + 759
33 UIKit 0x301d2e75 -[UIApplication sendEvent:] + 197
34 UIKit 0x301d1541 _UIApplicationHandleEventQueue + 7121
也许对于那些看起来很熟悉的人来说，他可以帮助理解问题的根源。