我遇到一个问题，即自动布局的屏幕在iOS 8上运行良好 - 但在iOS 7上崩溃了。 所有子视图都在XIB中配置。
错误消息是：
Terminating app due to uncaught exception 'NSGenericException', reason: 'Unable to install constraint on view.
Does the constraint reference something from outside the subtree of the view? That's illegal.
constraint:<NSLayoutConstraint:0x7ef80720 V:[UIImageView:0x7ef7fb40]-(0)-[UILabel:0x7ef802f0]> view:<UIView: 0x7ef7f1e0; frame = (0 0; 768 275); autoresize = RM+BM; layer = <CALayer: 0x7ef7f240>>'
这是堆栈跟踪：
(
0 CoreFoundation 0x0588a1e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x0563d8e5 objc_exception_throw + 44
2 CoreFoundation 0x05889fbb +[NSException raise:format:] + 139
3 Foundation 0x0284d55f -[NSLayoutConstraint _addToEngine:integralizationAdjustment:mutuallyExclusiveConstraints:] + 197
4 Foundation 0x028509ad -[NSLayoutConstraint _addToEngine:] + 56
5 UIKit 0x0460c974 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 515
6 Foundation 0x029c768c -[NSISEngine withBehaviors:performModifications:] + 107
7 Foundation 0x028573c5 -[NSISEngine withAutomaticOptimizationDisabled:] + 48
8 UIKit 0x0460ce40 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 63
9 UIKit 0x0460c754 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 476
10 UIKit 0x0460ce48 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 71
11 UIKit 0x0460c54f -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 223
12 UIKit 0x0460c46b -[UIView(AdditionalLayoutSupport) _parentalLayoutEngineDidChangeTo:] + 55
13 UIKit 0x0460c850 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 223
14 Foundation 0x029c768c -[NSISEngine withBehaviors:performModifications:] + 107
15 Foundation 0x028573c5 -[NSISEngine withAutomaticOptimizationDisabled:] + 48
16 UIKit 0x0460ce40 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 63
17 UIKit 0x0460c754 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 476
18 UIKit 0x0460ce48 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 71
19 UIKit 0x0460c54f -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 223
20 UIKit 0x0460c46b -[UIView(AdditionalLayoutSupport) _parentalLayoutEngineDidChangeTo:] + 55
21 UIKit 0x0460c850 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 223
22 Foundation 0x029c768c -[NSISEngine withBehaviors:performModifications:] + 107
23 Foundation 0x028573c5 -[NSISEngine withAutomaticOptimizationDisabled:] + 48
24 UIKit 0x0460ce40 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 63
25 UIKit 0x0460c754 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 476
26 UIKit 0x0460ce48 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 71
27 UIKit 0x0460c54f -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 223
28 UIKit 0x0460c46b -[UIView(AdditionalLayoutSupport) _parentalLayoutEngineDidChangeTo:] + 55
29 UIKit 0x03fd0948 __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke + 119
30 Foundation 0x029c768c -[NSISEngine withBehaviors:performModifications:] + 107
31 Foundation 0x028573c5 -[NSISEngine withAutomaticOptimizationDisabled:] + 48
32 UIKit 0x03fd0830 -[UIView(Hierarchy) _postMovedFromSuperview:] + 313
33 UIKit 0x03fdbdd4 -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1875
34 UIKit 0x03fcedba -[UIView(Hierarchy) addSubview:] + 56
35 UIKit 0x03f66645 -[_UIParallaxDimmingView didMoveToWindow] + 129
36 UIKit 0x03fd9478 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 1642
37 UIKit 0x03fd9109 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 763
38 UIKit 0x03fd096f __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke + 158
39 Foundation 0x029c768c -[NSISEngine withBehaviors:performModifications:] + 107
40 Foundation 0x028573c5 -[NSISEngine withAutomaticOptimizationDisabled:] + 48
41 UIKit 0x03fd0830 -[UIView(Hierarchy) _postMovedFromSuperview:] + 313
42 UIKit 0x03fdbdd4 -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1875
43 UIKit 0x03fcedba -[UIView(Hierarchy) addSubview:] + 56
44 UIKit 0x03f630f2 __53-[_UINavigationParallaxTransition animateTransition:]_block_invoke + 2001
45 UIKit 0x03fd581f +[UIView(Animation) performWithoutAnimation:] + 82
46 UIKit 0x03f624f6 -[_UINavigationParallaxTransition animateTransition:] + 1155
47 UIKit 0x040a93ae -[UINavigationController _startCustomTransition:] + 3446
48 UIKit 0x040b58f7 -[UINavigationController _startDeferredTransitionIfNeeded:] + 688
49 UIKit 0x040b64e9 -[UINavigationController __viewWillLayoutSubviews] + 57
50 UIKit 0x041f70d1 -[UILayoutContainerView layoutSubviews] + 213
51 UIKit 0x03fde964 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 355
52 libobjc.A.dylib 0x0564f82b -[NSObject performSelector:withObject:] + 70
53 QuartzCore 0x03dac45a -[CALayer layoutSublayers] + 148
54 QuartzCore 0x03da0244 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 380
55 QuartzCore 0x03da00b0 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 26
56 QuartzCore 0x03d067fa _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 294
57 QuartzCore 0x03d07b85 _ZN2CA11Transaction6commitEv + 393
58 QuartzCore 0x03dc55b0 +[CATransaction flush] + 52
59 UIKit 0x03f6d9bb _UIApplicationHandleEventQueue + 13095
60 CoreFoundation 0x0581377f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
61 CoreFoundation 0x0581310b __CFRunLoopDoSources0 + 235
62 CoreFoundation 0x058301ae __CFRunLoopRun + 910
63 CoreFoundation 0x0582f9d3 CFRunLoopRunSpecific + 467
64 CoreFoundation 0x0582f7eb CFRunLoopRunInMode + 123
65 GraphicsServices 0x06b4f5ee GSEventRunModal + 192
66 GraphicsServices 0x06b4f42b GSEventRun + 104
67 UIKit 0x03f6ff9b UIApplicationMain + 1225
68 Pageonce 0x000db639 main + 73
69 libdyld.dylib 0x064fe6d9 start + 1
）
问题是什么？
答案 0 :(得分：0)
原来这两行造成了崩溃：
self.ninjaStarImage.layer.removeFromSuperlayer()
self.view.layer.addSublayer(self.ninjaStarImage.layer)
将它们移至viewDidLayoutSubviews解决了问题