尝试添加文本字段时 iOS 8.3 UIAlertController 崩溃

Question

我有一个 iPad 应用程序。我正在创建一个 UIAlertController 并添加一个文本字段。它崩溃了。它仅在我添加文本字段时崩溃。

let alert = UIAlertController(title: "Enter Name", message:nil, preferredStyle: UIAlertControllerStyle.Alert);         
alert.addTextFieldWithConfigurationHandler { (textfield:UITextField!) -> Void in
                textfield.placeholder = "Sexy time";

            }
 alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: {(action:UIAlertAction!) -> Void in
      //Some action here   
 }));

 self.presentViewController(alert, animated: true, completion: nil);

我遇到了一个有趣的崩溃，告诉我约束被搞砸了。此代码在 < 8.3 中运行良好，没有警告。即使在一个除了这段代码什么都没有的干净项目上，它也会崩溃——该项目需要是 iPad 上的 splitview 项目。

这是完整的堆栈跟踪和奇怪的约束警告，它仅在尝试将文本字段添加到 alertController 后出现。

2015-04-10 15:25:07.155 Observation[18235:281813] The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x7fb66cf9dfc0 UITableView:0x7fb66b855000.left == UIView:0x7fb66fae68e0.left>
    When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
2015-04-10 15:25:07.155 Observation[18235:281813] The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x7fb66cf9e010 UITableView:0x7fb66b855000.right == UIView:0x7fb66fae68e0.right>
    When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
2015-04-10 15:25:07.155 Observation[18235:281813] The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x7fb66fb37f90 UITableView:0x7fb66b855000.top == UIView:0x7fb66fae68e0.top>
    When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
2015-04-10 15:25:07.156 Observation[18235:281813] The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x7fb66fb80580 UITableView:0x7fb66b855000.bottom == UIView:0x7fb66fae68e0.bottom>
    When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
2015-04-10 15:25:13.589 Observation[18235:281813] View hierarchy unprepared for constraint.
    Constraint: <NSLayoutConstraint:0x7fb66cf9dfc0 UITableView:0x7fb66b855000.left == UIView:0x7fb66fae68e0.left>
    Container hierarchy: 
<UIView: 0x7fb66fa86e00; frame = (0 0; 0 0); layer = <CALayer: 0x7fb66fadf8e0>>
   | <UIView: 0x7fb66af3e080; frame = (0 0; 0 0); clipsToBounds = YES; layer = <CALayer: 0x7fb66fae32c0>>
   |    | <_UIAlertControllerShadowedScrollView: 0x7fb66fa68c80; frame = (0 0; 0 0); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x7fb66fa38a80>; layer = <CALayer: 0x7fb66fa97560>; contentOffset: {0, 0}; contentSize: {0, 0}>
   |    |    | <UIView: 0x7fb66fa87350; frame = (0 0; 0 0); layer = <CALayer: 0x7fb66fadf810>>
   |    |    |    | <UILabel: 0x7fb66fa88740; frame = (0 0; 0 0); text = 'Enter Name'; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fb66fa94ed0>>
   |    |    |    | <UILabel: 0x7fb66fa73710; frame = (0 0; 0 0); userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fb66cc0ee10>>
   |    |    |    | <UIView: 0x7fb66fae68e0; frame = (0 0; 0 0); clipsToBounds = YES; layer = <CALayer: 0x7fb66fa90160>>
   |    | <UILabel: 0x7fb66fa3ad40; frame = (0 0; 0 0); userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fb66fa73680>>
   |    | <UICollectionView: 0x7fb66c130200; frame = (0 0; 0 0); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x7fb66faebab0>; layer = <CALayer: 0x7fb66fa3acf0>; contentOffset: {0, 0}; contentSize: {0, 0}> collection view layout: <_UIAlertControllerCollectionViewFlowLayout: 0x7fb66fae0b30>
    View not found in container hierarchy: <UITableView: 0x7fb66b855000; frame = (0 20; 768 1004); clipsToBounds = YES; autoresize = W+H; gestureRecognizers = <NSArray: 0x7fb66cf79f30>; layer = <CALayer: 0x7fb66cf600a0>; contentOffset: {0, 0}; contentSize: {768, 25}>
    That view's superview: NO SUPERVIEW
2015-04-10 15:25:13.594 Observation[18235:281813] *** 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:0x7fb66cf9dfc0 UITableView:0x7fb66b855000.left == UIView:0x7fb66fae68e0.left> view:<UIView: 0x7fb66fa86e00; frame = (0 0; 0 0); layer = <CALayer: 0x7fb66fadf8e0>>'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000102940c65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010221dbb7 objc_exception_throw + 45
    2   CoreFoundation                      0x0000000102940b9d +[NSException raise:format:] + 205
    3   Foundation                          0x0000000101daf479 -[NSLayoutConstraint _addToEngine:integralizationAdjustment:mutuallyExclusiveConstraints:] + 187
    4   UIKit                               0x00000001039bca34 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 474
    5   Foundation                          0x0000000101dbd1be -[NSISEngine withBehaviors:performModifications:] + 155
    6   UIKit                               0x00000001039bc83a __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 452
    7   UIKit                               0x00000001039bc64d -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 197
    8   UIKit                               0x00000001039bc933 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 217
    9   Foundation                          0x0000000101dbd1be -[NSISEngine withBehaviors:performModifications:] + 155
    10  UIKit                               0x00000001039bc83a __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 452
    11  UIKit                               0x00000001039bc64d -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 197
    12  UIKit                               0x00000001039bc933 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 217
    13  Foundation                          0x0000000101dbd1be -[NSISEngine withBehaviors:performModifications:] + 155
    14  UIKit                               0x00000001039bc83a __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 452
    15  UIKit                               0x00000001039bc64d -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 197
    16  UIKit                               0x00000001033b5717 __40-[UIView(Hierarchy) layoutBelowIfNeeded]_block_invoke + 39
    17  Foundation                          0x0000000101dbd1be -[NSISEngine withBehaviors:performModifications:] + 155
    18  UIKit                               0x00000001033b5556 -[UIView(Hierarchy) layoutBelowIfNeeded] + 320
    19  UIKit                               0x000000010374a394 -[_UIAlertControllerAnimatedTransitioning animateTransition:] + 470
    20  UIKit                               0x000000010344fa4e __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 1867
    21  UIKit                               0x000000010336562c _applyBlockToCFArrayCopiedToStack + 314
    22  UIKit                               0x00000001033654a6 _afterCACommitHandler + 533
    23  CoreFoundation                      0x0000000102873ca7 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
    24  CoreFoundation                      0x0000000102873c00 __CFRunLoopDoObservers + 368
    25  CoreFoundation                      0x0000000102869a33 __CFRunLoopRun + 1123
    26  CoreFoundation                      0x0000000102869366 CFRunLoopRunSpecific + 470
    27  GraphicsServices                    0x0000000106dd6a3e GSEventRunModal + 161
    28  UIKit                               0x0000000103341900 UIApplicationMain + 1282
    29  Observation                         0x0000000101612927 main + 135
    30  libdyld.dylib                       0x0000000104f60145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

编辑:此修复会根据您是使用 Xcode 6 还是 Xcode 7 进行构建而发生变化，因此我添加了两个版本的 Xcode 的相关信息。

---

我今天遇到了这个问题，它的意思是它无法将文本字段添加到 View Controller 的 View 中，或者它无法将自动布局约束添加到其父 View 中。这似乎是因为它还没有创建要将其添加到的 super View ，所以它会出现 panic 和崩溃。

我发现的简单修复是在告诉警报 Controller 显示后添加文本字段。这对我来说是固定的，但我不确定它是否会影响任何东西，比如在出现警报时弹出的文本字段。

使用 Xcode 6 构建

let alertController = UIAlertController(title: "Enter Name", message:nil, preferredStyle: .Alert)

let okAction = UIAlertAction(title: "Ok", style: .Default) { (_) -> Void in
    // Some action here
}
alertController.addAction(okAction)

presentViewController(alertController, animated: true, completion: nil)

// Add any text fields after presenting the alert controller to fix crash in iOS 8.3
alertController.addTextFieldWithConfigurationHandler { (textfield) -> Void in
    textfield.placeholder = "Name"
}

附言作为代码示例的旁注，请记住使用 Swift，您不需要在每一行的末尾使用 ; ，尽管这样做并不重要。 😉

---

使用 Xcode 7 构建

当您使用 Xcode 7 构建应用程序时，Apple 似乎已经解决了这个问题。使用上面显示的方法将不再在 iOS 9 中显示文本字段(即使它在 iOS 8 中仍能正确显示)。

下面是一段代码，它本来应该是这样的，当在 Xcode 7 中构建时，它可以在 iOS 8 和 iOS 9 中正确运行。

let alertController = UIAlertController(title: "Enter Name", message:nil, preferredStyle: .Alert)

alertController.addTextFieldWithConfigurationHandler { (textfield) -> Void in
    textfield.placeholder = "Name"
}

let okAction = UIAlertAction(title: "Ok", style: .Default) { (_) -> Void in
    // Some action here
}
alertController.addAction(okAction)

presentViewController(alertController, animated: true, completion: nil)

使用 Xcode 7 GM (7A218) 在 Swift 2.0 和 Obj-C 中测试