ios - 为什么 iOS 在尝试以相反的顺序显示排序结果时会崩溃？
问题描述
我有一个按部分显示信息的 SwiftUI 应用程序。当按下按钮时，我想对节标题以及每个节的内容进行升序或降序排序（即，按钮反转当前的排序顺序。
按下按钮时，应用程序立即崩溃并出现以下错误。我已经简化了代码以轻松重现问题。在真实的应用程序中，除非您滚动数据然后排序，否则应用程序不会崩溃。
我怎样才能在没有崩溃的情况下达到预期的结果？任何帮助或指示将不胜感激。
Catalina 10.15.2
Xcode 11.3
iOS 13.3
2020-01-29 22:31:07.837639-0800 sections[33051:9858192] *** Assertion failure in -[_UITableViewUpdateSupport _setupAnimationsForNewlyInsertedCells], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKitCore_Sim/UIKit-3901.4.2/UITableViewSupport.m:1311
2020-01-29 22:31:07.847803-0800 sections[33051:9858192] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Attempt to create two animations for cell'
*** First throw call stack:
(
0 CoreFoundation 0x00007fff23c7127e __exceptionPreprocess + 350
1 libobjc.A.dylib 0x00007fff513fbb20 objc_exception_throw + 48
2 CoreFoundation 0x00007fff23c70ff8 +[NSException raise:format:arguments:] + 88
3 Foundation 0x00007fff256e9b51 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 191
4 UIKitCore 0x00007fff482c3979 -[_UITableViewUpdateSupport(Private) _setupAnimationsForNewlyInsertedCells] + 1575
5 UIKitCore 0x00007fff482ce773 -[_UITableViewUpdateSupport _setupAnimations] + 118
6 UIKitCore 0x00007fff48265026 -[UITableView _updateWithItems:updateSupport:] + 2892
7 UIKitCore 0x00007fff4825cfd4 -[UITableView _endCellAnimationsWithContext:] + 17188
8 UIKitCore 0x00007fff48276e0b -[UITableView endUpdatesWithContext:] + 112
9 UIKitCore 0x00007fff48276fb7 -[UITableView _performBatchUpdates:withContext:completion:] + 253
10 UIKitCore 0x00007fff482770cf -[UITableView performBatchUpdates:completion:] + 98
11 SwiftUI 0x00007fff2c24ea26 $s7SwiftUI25UpdateCoalescingTableView33_BFB370BA5F1BADDC9D83021565761A49LLC19performBatchUpdates_10completionyyycSg_ySbcSgtF + 470
12 SwiftUI 0x00007fff2c24ebaf $s7SwiftUI25UpdateCoalescingTableView33_BFB370BA5F1BADDC9D83021565761A49LLC19performBatchUpdates_10completionyyycSg_ySbcSgtFTo + 175
13 SwiftUI 0x00007fff2c2510cc $s7SwiftUI19ListCoreCoordinator33_BFB370BA5F1BADDC9D83021565761A49LLC17updateUITableView_4from2toySo0mN0C_xxtF + 1692
14 SwiftUI 0x00007fff2c24f9ed $s7SwiftUI9_ListCore33_BFB370BA5F1BADDC9D83021565761A49LLV12updateUIView_7contextyAA12TableWrapperACLLC_AA0L20RepresentableContextVyADyxq_GGtF + 973
15 SwiftUI 0x00007fff2c6149c1 $s7SwiftUI32PlatformViewRepresentableAdaptor33_19642D833A8FE469B137699ED1426762LLV06updateD8Provider_7contexty10UIViewTypeQz_AA0cdE7ContextVyADyxGGtF + 289
16 SwiftUI 0x00007fff2c2c6afb $s7SwiftUI17PlatformViewChild33_A513612C07DFA438E70B9FA90719B40DLLV6update7contexty14AttributeGraph0O7ContextVyADyxGGz_tFyyXEfU_ + 2315
17 SwiftUI 0x00007fff2c2c07f6 $s7SwiftUI17PlatformViewChild33_A513612C07DFA438E70B9FA90719B40DLLV6update7contexty14AttributeGraph0O7ContextVyADyxGGz_tF + 310
18 SwiftUI 0x00007fff2c2c7e60 $s7SwiftUI17PlatformViewChild33_A513612C07DFA438E70B9FA90719B40DLLVyxG14AttributeGraph07UntypedM0AafGP7_update_5graph9attributeySv_So10AGGraphRefaSo11AGAttributeatFZTW + 32
19 AttributeGraph 0x00007fff2f8c0c69 $sTA + 25
20 AttributeGraph 0x00007fff2f8a8ac5 _ZN2AG5Graph11UpdateStack6updateEv + 1111
21 AttributeGraph 0x00007fff2f8a8d83 _ZN2AG5Graph16update_attributeEjb + 377
22 AttributeGraph 0x00007fff2f8ad9a1 _ZN2AG8Subgraph6updateEj + 929
23 SwiftUI 0x00007fff2c180405 $s7SwiftUI9ViewGraphC13updateWrapperyyyyXEcvgyyyXEcfU_yACXEfU_ + 53
24 SwiftUI 0x00007fff2c185c11 $s7SwiftUI9ViewGraphCIgg_ACytIeggr_TRTA + 17
25 SwiftUI 0x00007fff2c4cbdd7 $s7SwiftUI16ViewRendererHostPAAE06updateC5Graph4bodyqd__qd__AA0cG0CXE_tlF + 71
26 SwiftUI 0x00007fff2c4cbd83 $s7SwiftUI14_UIHostingViewCyqd__GAA0D13GraphDelegateA2aEP06updatedE04bodyqd__qd__AA0dE0CXE_tlFTW + 19
27 SwiftUI 0x00007fff2c1803a5 $s7SwiftUI9ViewGraphC13updateWrapperyyyyXEcvgyyyXEcfU_ + 181
28 AttributeGraph 0x00007fff2f8ad890 _ZN2AG8Subgraph6updateEj + 656
29 SwiftUI 0x00007fff2c1826c0 $s7SwiftUI9ViewGraphC14runTransaction33_D63C4EB7F2B205694B6515509E76E98BLL2inySo10AGGraphRefa_tF + 224
30 SwiftUI 0x00007fff2c182490 $s7SwiftUI9ViewGraphC17flushTransactionsyyFySo10AGGraphRefaXEfU_ + 256
31 SwiftUI 0x00007fff2c18212f $s7SwiftUI9ViewGraphC17flushTransactionsyyF + 223
32 SwiftUI 0x00007fff2c1822af $s7SwiftUI9ViewGraphC16asyncTransaction_8mutation5styleyAA0F0V_xAA01_D14Mutation_StyleOtAA0dI0RzlFyycfU_yACXEfU_ + 15
33 SwiftUI 0x00007fff2c180439 $s7SwiftUI9ViewGraphCIgg_ACytIeggr_TR03$s7a3UI9cD92C16asyncTransaction_8mutation5styleyAA0F0V_xAA01_D14Mutation_StyleOtAA0dI0RzlFyycfU_yACXEfU_Tf3nnpf_n + 9
34 SwiftUI 0x00007fff2c4cbdd7 $s7SwiftUI16ViewRendererHostPAAE06updateC5Graph4bodyqd__qd__AA0cG0CXE_tlF + 71
35 SwiftUI 0x00007fff2c4cbd83 $s7SwiftUI14_UIHostingViewCyqd__GAA0D13GraphDelegateA2aEP06updatedE04bodyqd__qd__AA0dE0CXE_tlFTW + 19
36 SwiftUI 0x00007fff2c18228a $s7SwiftUI9ViewGraphC16asyncTransaction_8mutation5styleyAA0F0V_xAA01_D14Mutation_StyleOtAA0dI0RzlFyycfU_ + 122
37 SwiftUI 0x00007fff2c1a078c $sIeg_ytIegr_TR + 12
38 SwiftUI 0x00007fff2bfe3261 $sIeg_ytIegr_TRTA + 17
39 SwiftUI 0x00007fff2bfe3187 $sSo9NSRunLoopC7SwiftUIE14flushObserversyyFZ + 119
40 SwiftUI 0x00007fff2bfe3109 $sSo9NSRunLoopC7SwiftUIE11addObserveryyyycFZySo05CFRunbF3RefaSg_So0gB8ActivityVSvSgtcfU_ + 9
41 SwiftUI 0x00007fff2bfe31fb $sSo9NSRunLoopC7SwiftUIE11addObserveryyyycFZySo05CFRunbF3RefaSg_So0gB8ActivityVSvSgtcfU_To + 43
42 CoreFoundation 0x00007fff23bd3867 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
43 CoreFoundation 0x00007fff23bce2fe __CFRunLoopDoObservers + 430
44 CoreFoundation 0x00007fff23bce97a __CFRunLoopRun + 1514
45 CoreFoundation 0x00007fff23bce066 CFRunLoopRunSpecific + 438
46 GraphicsServices 0x00007fff384c0bb0 GSEventRunModal + 65
47 UIKitCore 0x00007fff48092d4d UIApplicationMain + 1621
48 sections 0x000000010af50bbb main + 75
49 libdyld.dylib 0x00007fff5227ec25 start + 1
50 ??? 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
//
// ContentView.swift
// sections
//
import SwiftUI
struct ContentView: View {
@State private var ascending: Bool = true
var body: some View {
VStack {
Button(action: {
self.ascending.toggle()
}) {
if self.ascending {
Text("Sort Descending")
} else {
Text("Sort Ascending")
}
}
SectionView(boats: [Boat(name: "B1", number: "1"),
Boat(name: "B2", number: "2"),
Boat(name: "B3", number: "3"),
Boat(name: "B22", number: "22"),
Boat(name: "B24", number: "24"),
Boat(name: "B333", number: "333"),
Boat(name: "B4", number: "3"),
Boat(name: "B5", number: "3"),
], ascending: ascending)
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
//
// SectionView.swift
// sections
//
import SwiftUI
struct Boat: Hashable {
var id = UUID()
var name: String
var number: String
}
struct SectionView: View {
var boats = [Boat]()
var ascending: Bool
var body: some View {
NavigationView {
List {
ForEach (self.classDictionary(ascending: ascending), id: \.0) { key, boats in
Section(header: Text("\(key)").font(.caption).bold()) {
ForEach (boats, id: \.self) { boat in
NavigationLink(destination: DetailView(boat: boat)) {
Text(boat.name)
}
}
}
}
}
}
}
//
func classDictionary(ascending: Bool) -> [(key: String, boats: [Boat])] {
var returnTuple = [(key: String, boats: [Boat])]()
let groupedDictionary = Dictionary(grouping: self.boats, by: {String(numberOfDigits(in: Int($0.number)!))})
for (key, boats) in groupedDictionary {
returnTuple.append((key, boats))
}
if ascending {
returnTuple = returnTuple.sorted(by: { $0.boats.map { Int($0.number)!}.min() ?? 0 < $1.boats.map { Int($0.number)!}.min() ?? 0 })
} else {
returnTuple = returnTuple.sorted(by: { $0.boats.map { Int($0.number)!}.max() ?? 0 > $1.boats.map { Int($0.number)!}.max() ?? 0 })
}
return returnTuple
}
// private recursive method for counting digits
private func numberOfDigits(in number: Int) -> Int {
if number < 10 && number >= 0 || number > -10 && number < 0 {
return 1
} else {
return 1 + numberOfDigits(in: number/10)
}
}
}
struct SectionView_Previews: PreviewProvider {
static var ascending: Bool = true
static var previews: some View {
VStack {
Button(action: {
self.ascending.toggle()
}) {
if self.ascending {
Text("Sort Descending")
} else {
Text("Sort Ascending")
}
// Text("Change Sort")
}
SectionView(boats: [Boat(name: "B1", number: "1"),
Boat(name: "B2", number: "2"),
Boat(name: "B3", number: "3"),
Boat(name: "B22", number: "22"),
Boat(name: "B24", number: "24"),
Boat(name: "B333", number: "333"),
Boat(name: "B4", number: "3"),
Boat(name: "B5", number: "3"),
], ascending: ascending)
}
}
}
struct DetailView: View {
var boat: Boat
var body: some View {
Text(boat.name)
}
}
解决方案
问题的根源在于内容标识符......因此更改以下几行可修复崩溃
1)
ForEach (self.classDictionary(ascending: ascending), id: \.1) { key, boats in
注意：出于性能目的，我建议改为使用自己的 UUID 作为 id 为 Section 数据创建显式结构。
2)
ForEach (boats, id: \.id) { boat in
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