所以我最近遇到了一个我们团队无法解决的Sigabrt崩溃。它涉及到segue崩溃。当我按下信息视图控制器中的学校规则按钮时，它会将（执行segue）推送到学校规则视图控制器。但是，当我按下后退按钮（在顶部的导航栏上）时，它会返回到信息视图控制器，但随后会崩溃。以下是我的崩溃日志和视图控制器：
注意：我已检查所有正常的Sigabrt崩溃，包括链接插座，Segue标识符等。
Application did finish launching
2018-04-29 11:13:47.156002+0800 DBS[6288:361798] Simulator user has requested new graphics quality: 100
DidDisappear ()
true
(8.0, 8.0, 375.0, 812.0)
(8.0, 145.111111111111, 359.0, 521.777777777778)
2018-04-29 11:14:19.188187+0800 DBS[6288:361798] [general] Caught exception during autorelease pool drain NSGenericException: Unable to activate constraint with anchors <NSLayoutYAxisAnchor:0x600000669700 "DBS.dropDownView:0x7fcda1537890.top"> and <NSLayoutYAxisAnchor:0x60000066a300 "DBS.dropDownBtn:0x7fcda1538510'▼ Introduction'.bottom"> because they have no common ancestor. Does the constraint or its anchors reference items in different view hierarchies? That's illegal. userInfo: (null)
2018-04-29 11:14:19.203034+0800 DBS[6288:361798] *** Terminating app due to uncaught exception 'NSGenericException', reason: 'Unable to activate constraint with anchors <NSLayoutYAxisAnchor:0x600000669700 "DBS.dropDownView:0x7fcda1537890.top"> and <NSLayoutYAxisAnchor:0x60000066a300 "DBS.dropDownBtn:0x7fcda1538510'▼ Introduction'.bottom"> because they have no common ancestor. Does the constraint or its anchors reference items in different view hierarchies? That's illegal.'
*** First throw call stack:
(
0 CoreFoundation 0x000000010adbe1e6 __exceptionPreprocess + 294
1 libobjc.A.dylib 0x000000010a00c031 objc_exception_throw + 48
2 CoreFoundation 0x000000010ae33975 +[NSException raise:format:] + 197
3 DBS 0x0000000107f64206 _T03DBS11dropDownBtnC18didMoveToSuperviewyyF + 566
4 DBS 0x0000000107f644b4 _T03DBS11dropDownBtnC18didMoveToSuperviewyyFTo + 36
5 UIKit 0x000000010c5f7400 __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke + 899
6 UIKit 0x000000010c5f6fea -[UIView(Hierarchy) _postMovedFromSuperview:] + 808
7 UIKit 0x000000010c5f4e9e __UIViewWasRemovedFromSuperview + 169
8 UIKit 0x000000010c5f4990 -[UIView(Hierarchy) removeFromSuperview] + 479
9 UIKit 0x000000010c5ddc67 -[UIView dealloc] + 508
10 libobjc.A.dylib 0x000000010a0211b2 _ZN12_GLOBAL__N_119AutoreleasePoolPage3popEPv + 860
11 CoreFoundation 0x000000010ad08136 _CFAutoreleasePoolPop + 22
12 CoreFoundation 0x000000010ad44eae __CFRunLoopRun + 2350
13 CoreFoundation 0x000000010ad4430b CFRunLoopRunSpecific + 635
14 GraphicsServices 0x000000011396ca73 GSEventRunModal + 62
15 UIKit 0x000000010c53f0b7 UIApplicationMain + 159
16 DBS 0x0000000107f68507 main + 55
17 libdyld.dylib 0x000000010f37d955 start + 1
18 ??? 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
下面是我的DropDownButton视图控制器：
import UIKit
protocol dropDownProtocol {
func dropDownPressed(string : String)
}
class dropDownBtn: UIButton, dropDownProtocol {
func dropDownPressed(string: String) {
self.setTitle("▼ \(string)", for: .normal)
self.titleLabel?.adjustsFontSizeToFitWidth = true
self.dismissDropDown()
}
var dropView = dropDownView()
var height = NSLayoutConstraint()
override init(frame: CGRect) {
super.init(frame: frame)
self.backgroundColor = UIColor.lightGray
dropView = dropDownView.init(frame: CGRect.init(x: 8, y: 100, width: 0, height: 0))
dropView.delegate = self
dropView.translatesAutoresizingMaskIntoConstraints = false
}
override func didMoveToSuperview() {
self.superview?.addSubview(dropView)
self.superview?.bringSubview(toFront: dropView)
dropView.topAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
dropView.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
dropView.widthAnchor.constraint(equalTo: self.widthAnchor).isActive = true
height = dropView.heightAnchor.constraint(equalToConstant: 0)
}
var isOpen = false
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if isOpen == false {
isOpen = true
NSLayoutConstraint.deactivate([self.height])
// if self.dropView.tableView.contentSize.height > 400 {
// self.height.constant = 400
// } else {
// self.height.constant = self.dropView.tableView.contentSize.height
// }
self.height.constant = self.dropView.tableView.contentSize.height+8
NSLayoutConstraint.activate([self.height])
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.5, initialSpringVelocity: 0.5, options: .curveEaseInOut, animations: {
self.dropView.layoutIfNeeded()
self.dropView.center.y += self.dropView.frame.height / 2
}, completion: nil)
} else {
isOpen = false
NSLayoutConstraint.deactivate([self.height])
self.height.constant = 0
NSLayoutConstraint.activate([self.height])
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.5, initialSpringVelocity: 0.5, options: .curveEaseInOut, animations: {
self.dropView.center.y -= self.dropView.frame.height / 2
self.dropView.layoutIfNeeded()
}, completion: nil)
}
}
func dismissDropDown() {
isOpen = false
NSLayoutConstraint.deactivate([self.height])
self.height.constant = 0
NSLayoutConstraint.activate([self.height])
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.5, initialSpringVelocity: 0.5, options: .curveEaseInOut, animations: {
self.dropView.center.y -= self.dropView.frame.height / 2
self.dropView.layoutIfNeeded()
}, completion: nil)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
答案 0 :(得分：1)
您的didMoveToSuperview函数假定仅在将视图添加到其超级视图时才会调用它。但是当它从超级视图中删除时也会调用它。如果查看堆栈跟踪，可以看到在删除视图时发生崩溃。您需要更新didMoveToSuperview，以便它只在添加时运行代码，而不是在删除时运行。
override func didMoveToSuperview() {
if let superview = self.superview {
superview.addSubview(dropView)
superview.bringSubview(toFront: dropView)
dropView.topAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
dropView.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
dropView.widthAnchor.constraint(equalTo: self.widthAnchor).isActive = true
height = dropView.heightAnchor.constraint(equalToConstant: 0)
}
}