我在添加 NewsAndInformationDetailCommentView 自定义 View (来自 xib)作为另一个 View 的 subview 时遇到问题。
在此自定义 View 内，添加了一些组件，每个组件上几乎没有约束。
这里是自定义 View 代码。
import UIKit
class NewsAndInformationDetailCommentView: UIView {
@IBOutlet weak var view: UIView!
// the subviews
@IBOutlet weak var profileImageView: UIImageView!
@IBOutlet weak var createdByLabel: UILabel!
@IBOutlet weak var comment: UITextView!
@IBOutlet weak var createdAtLabel: UILabel!
override init(frame: CGRect) {
super.init(frame: frame)
prepare()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
prepare()
}
private func prepare() {
let view = Bundle.main.loadNibNamed(String(describing: NewsAndInformationDetailCommentView.self), owner: self, options: nil)?[0] as! UIView
self.addSubview(view)
view.backgroundColor = .clear
view.frame = self.frame
view.translatesAutoresizingMaskIntoConstraints = false
view.addConstraints([
NSLayoutConstraint(item: view, attribute: .leading, relatedBy: .equal, toItem: self, attribute: .leading, multiplier: 1.0, constant: 0),
NSLayoutConstraint(item: view, attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailing, multiplier: 1.0, constant: 0),
NSLayoutConstraint(item: view, attribute: .top, relatedBy: .equal, toItem: self, attribute: .top, multiplier: 1.0, constant: 0),
NSLayoutConstraint(item: view, attribute: .bottom, relatedBy: .equal, toItem: self, attribute: .bottom, multiplier: 1.0, constant: 0)
])
}
}
这是 xib 的屏幕截图。
在父 View 上，这是添加 subview 的方式。这非常简单。
let commentView = NewsAndInformationDetailCommentView(frame: CGRect(x: 0, y: previousItem.frame.origin.y + previousItem.frame.size.height, width: contentOfScrollView.frame.size.width, height: defaultHeight))
contentOfScrollView.addSubview(commentView)
当我运行该应用程序时，它崩溃了。并出现下面的堆栈跟踪。
2019-08-03 15:52:23.179570+0700 Satpam Mantab[44304:1673267] [LayoutConstraints] The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x600001628dc0 H:|-(0)-[UIView:0x7fc9444401d0] (inactive, names: '|':Satpam_Mantab.NewsAndInformationDetailCommentView:0x7fc94462a220 )>
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(UIConstraintBasedLayout) _viewHierarchyUnpreparedForConstraint:] to debug.
------- Optional(<Satpam_Mantab.NewsAndInformationDetailCommentView: 0x7fc94462a220; frame = (0 523; 320 200); layer = <CALayer: 0x600003508b80>>)
2019-08-03 15:52:23.190358+0700 Satpam Mantab[44304:1673267] [LayoutConstraints] View hierarchy unprepared for constraint.
Constraint: <NSLayoutConstraint:0x600001628dc0 H:|-(0)-[UIView:0x7fc9444401d0] (active, names: '|':Satpam_Mantab.NewsAndInformationDetailCommentView:0x7fc94462a220 )>
Container hierarchy:
<UIView: 0x7fc9444401d0; frame = (0 523; 320 200); autoresize = RM+BM; layer = <CALayer: 0x600003503400>>
| <UITextView: 0x7fc9460a6000; frame = (60 31; 343 49); text = 'Lorem Lorem Lorem Lorem L...'; clipsToBounds = YES; autoresize = RM+BM; gestureRecognizers = <NSArray: 0x600003b33c90>; layer = <CALayer: 0x600003502c40>; contentOffset: {0, 0}; contentSize: {343, 41}; adjustedContentInset: {0, 0, 0, 0}>
| | <<_UITextContainerView: 0x7fc94443eaf0; frame = (0 0; 343 49); layer = <__UITextTiledLayer: 0x60000117f7e0>> minSize = {0, 0}, maxSize = {1.7976931348623157e+308, 1.7976931348623157e+308}, textContainer = <NSTextContainer: 0x60000076c900 size = (343.000000,inf); widthTracksTextView = YES; heightTracksTextView = YES>; exclusionPaths = 0x600003770050; lineBreakMode = 0>
| <UIView: 0x7fc9444403b0; frame = (15 15; 384 40); autoresize = RM+BM; layer = <CALayer: 0x600003503420>>
| | <UIView: 0x7fc944440590; frame = (0 0; 40 40); autoresize = RM+BM; layer = <CALayer: 0x600003503440>>
| | | <UIImageView: 0x7fc94443ffa0; frame = (0 0; 40 40); clipsToBounds = YES; autoresize = RM+BM; userInteractionEnabled = NO; layer = <CALayer: 0x600003503020>>
| | <UILabel: 0x7fc944521480; frame = (50 0; 39 20); text = 'admin'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x6000016221c0>>
| <UILabel: 0x7fc94443f820; frame = (65 80; 334 20); text = '15 Juli 2019'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x600001622080>>
View not found in container hierarchy: <Satpam_Mantab.NewsAndInformationDetailCommentView: 0x7fc94462a220; frame = (0 523; 320 200); layer = <CALayer: 0x600003508b80>>
That view's superview: <UIView: 0x7fc9446042c0; frame = (0 -400; 320 1000); autoresize = RM+BM; layer = <CALayer: 0x600003523260>>
2019-08-03 15:52:23.217853+0700 Satpam Mantab[44304:1673267] *** 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:0x600001628dc0 H:|-(0)-[UIView:0x7fc9444401d0] (active, names: '|':Satpam_Mantab.NewsAndInformationDetailCommentView:0x7fc94462a220 )> view:<UIView: 0x7fc9444401d0; frame = (0 523; 320 200); autoresize = RM+BM; layer = <CALayer: 0x600003503400>>'
*** First throw call stack:
(
0 CoreFoundation 0x00000001105ec8db __exceptionPreprocess + 331
1 libobjc.A.dylib 0x000000010fb8fac5 objc_exception_throw + 48
2 CoreFoundation 0x00000001105ec735 +[NSException raise:format:] + 197
3 Foundation 0x000000010f7e7943 -[NSLayoutConstraint _addToEngine:mutuallyExclusiveConstraints:] + 205
4 UIKitCore 0x000000011959bce6 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 456
5 Foundation 0x000000010f7d0f46 -[NSISEngine withBehaviors:performModifications:] + 110
6 UIKitCore 0x000000011959baf7 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 571
7 UIKitCore 0x000000011959b884 -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 217
8 UIKitCore 0x000000011959bbf3 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 213
9 Foundation 0x000000010f7d0f46 -[NSISEngine withBehaviors:performModifications:] + 110
10 UIKitCore 0x000000011959baf7 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 571
11 UIKitCore 0x000000011959b884 -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 217
12 UIKitCore 0x000000011964d96f __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke + 112
13 UIKitCore 0x000000011964d875 -[UIView(Hierarchy) _postMovedFromSuperview:] + 795
14 UIKitCore 0x000000011965dae5 -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1948
15 Satpam Mantab 0x000000010d8096e4 $s13Satpam_Mantab38NewsAndInformationDetailViewControllerC21viewDidLayoutSubviewsyyFyAA0cdE12CommentModelCXEfU_ + 1060
16 Satpam Mantab 0x000000010d80a387 $s13Satpam_Mantab38NewsAndInformationDetailViewControllerC21viewDidLayoutSubviewsyyFyAA0cdE12CommentModelCXEfU_TA + 23
17 Satpam Mantab 0x000000010d80a3a9 $s13Satpam_Mantab30NewsAndInformationCommentModelCs5Error_pIggzo_ACsAD_pIegnzo_TR + 25
18 Satpam Mantab 0x000000010d80a43b $s13Satpam_Mantab30NewsAndInformationCommentModelCs5Error_pIggzo_ACsAD_pIegnzo_TRTA + 27
19 libswiftCore.dylib 0x00000001116cc9e4 $sSTsE7forEachyyy7ElementQzKXEKF + 452
20 Satpam Mantab 0x000000010d809226 $s13Satpam_Mantab38NewsAndInformationDetailViewControllerC21viewDidLayoutSubviewsyyF + 5014
21 Satpam Mantab 0x000000010d80a584 $s13Satpam_Mantab38NewsAndInformationDetailViewControllerC21viewDidLayoutSubviewsyyFTo + 36
22 UIKitCore 0x0000000119663fe8 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1800
23 QuartzCore 0x000000010f2cad22 -[CALayer layoutSublayers] + 173
24 QuartzCore 0x000000010f2cf9fc _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 396
25 QuartzCore 0x000000010f2dbd58 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 72
26 QuartzCore 0x000000010f24b24a _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 328
27 QuartzCore 0x000000010f282606 _ZN2CA11Transaction6commitEv + 610
28 UIKitCore 0x00000001191ac99c _afterCACommitHandler + 245
29 CoreFoundation 0x00000001105532c7 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
30 CoreFoundation 0x000000011054d78e __CFRunLoopDoObservers + 430
31 CoreFoundation 0x000000011054de01 __CFRunLoopRun + 1505
32 CoreFoundation 0x000000011054d4d2 CFRunLoopRunSpecific + 626
33 GraphicsServices 0x000000011676d2fe GSEventRunModal + 65
34 UIKitCore 0x0000000119184fc2 UIApplicationMain + 140
35 Satpam Mantab 0x000000010d82938b main + 75
36 libdyld.dylib 0x0000000112b7f541 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
我尝试调试代码多次，发现下面这行代码是触发错误的代码。
view.addConstraints([
NSLayoutConstraint(item: view, attribute: .leading, relatedBy: .equal, toItem: self, attribute: .leading, multiplier: 1.0, constant: 0),
...
])
如果我删除上述约束代码，则应用程序可以顺利运行。它本身的约束基本上是将 View 设置为相对于父 View (所有者)。如果没有约束， View 的框架将会困惑。所以我需要它。
我应该怎么做才能消除错误？ (保持约束而不会出现任何错误)
最佳答案
尝试让self添加约束:
addConstraints([
NSLayoutConstraint(item: view, attribute: .leading, relatedBy: .equal, toItem: self, attribute: .leading, multiplier: 1.0, constant: 0),
NSLayoutConstraint(item: view, attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailing, multiplier: 1.0, constant: 0),
NSLayoutConstraint(item: view, attribute: .top, relatedBy: .equal, toItem: self, attribute: .top, multiplier: 1.0, constant: 0),
NSLayoutConstraint(item: view, attribute: .bottom, relatedBy: .equal, toItem: self, attribute: .bottom, multiplier: 1.0, constant: 0)
])
关于ios - 带有导致崩溃的约束的自定义 View (xib)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/57336991/