Ios collectionview scrollToItemAtIndexPath应用程序崩溃

因此，我在viewDidLoad函数中放置了以下代码，它会使应用程序崩溃。你知道为什么会发生这种情况，或者有什么办法吗

self.collectionView?.scrollToItem(at: IndexPath(row: 0, section: 0), at: .top, animated: true)

---------------编辑--------------- 添加了错误日志

2016-12-26 18:40:08.354 ParseStarterProject-Swift[73829:1561943] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'attempt to scroll to invalid index path: <NSIndexPath: 0x608000226400> {length = 2, path = 0 - 0}'
*** First throw call stack:
(
    0   CoreFoundation                      0x00000001066e7d4b __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x000000010614921e objc_exception_throw + 48
    2   CoreFoundation                      0x00000001067512b5 +[NSException raise:format:] + 197
    3   UIKit                               0x0000000107fb0e44 -[UICollectionView scrollToItemAtIndexPath:atScrollPosition:animated:] + 224
    4   ParseStarterProject-Swift           0x00000001051a963c _TFC25ParseStarterProject_Swift18PackViewController13viewDidAppearfSbT_ + 700
    5   ParseStarterProject-Swift           0x00000001051a9741 _TToFC25ParseStarterProject_Swift18PackViewController13viewDidAppearfSbT_ + 49
    6   UIKit                               0x0000000107808a6c -[UIViewController _setViewAppearState:isAnimating:] + 945
    7   UIKit                               0x0000000107809388 -[UIViewController _endAppearanceTransition:] + 197
    8   UIKit                               0x00000001077de28d -[UIPresentationController transitionDidFinish:] + 834
    9   UIKit                               0x00000001079f5f83 -[_UICurrentContextPresentationController transitionDidFinish:] + 42
    10  UIKit                               0x00000001077e1ef0 __56-[UIPresentationController runTransitionForCurrentState]_block_invoke_2 + 183
    11  UIKit                               0x00000001081a356c -[_UIViewControllerTransitionContext completeTransition:] + 102
    12  UIKit                               0x00000001077daddc -[UITransitionView notifyDidCompleteTransition:] + 251
    13  UIKit                               0x00000001077daaef -[UITransitionView _didCompleteTransition:] + 1539
    14  UIKit                               0x00000001077dd51c -[UITransitionView _transitionDidStop:finished:] + 104
    15  UIKit                               0x00000001076edbd5 -[UIViewAnimationState sendDelegateAnimationDidStop:finished:] + 222
    16  UIKit                               0x00000001076ee12a -[UIViewAnimationState animationDidStop:finished:] + 136
    17  QuartzCore                          0x0000000107392648 _ZN2CA5Layer23run_animation_callbacksEPv + 316
    18  libdispatch.dylib                   0x00000001098940cd _dispatch_client_callout + 8
    19  libdispatch.dylib                   0x00000001098748a4 _dispatch_main_queue_callback_4CF + 406
    20  CoreFoundation                      0x00000001066abe49 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
    21  CoreFoundation                      0x000000010667137d __CFRunLoopRun + 2205
    22  CoreFoundation                      0x0000000106670884 CFRunLoopRunSpecific + 420
    23  GraphicsServices                    0x000000010bf76a6f GSEventRunModal + 161
    24  UIKit                               0x0000000107660c68 UIApplicationMain + 159
    25  ParseStarterProject-Swift           0x00000001051966cf main + 111
    26  libdyld.dylib                       0x00000001098e068d start + 1
    27  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) 

2016-12-26 18:40:08.354 ParseStarter项目Swift[73829:1561943]***由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“尝试滚动到无效的索引路径：{length=2，path=0-0}”
***第一次抛出调用堆栈：
(
0 CoreFoundation 0x00000001066e7d4b例外预处理+171
1 libobjc.A.dylib 0x000000010614921e objc_异常_抛出+48
2 CoreFoundation 0x00000001067512b5+[N异常提升：格式：][197
3 UIKit 0x0000000107fb0e44-[UICollectionView scrollToItemAtIndexPath:atScrollPosition:animated:+224
4项目Swift 0x00000001051a963c\u TFC25ParseStarterProject\u SWIFT18PACKVIEWCONTROLLER 13VIEWDIDAPEARFSBT+700
5 ParseStarter项目Swift 0x00000001051a9741 _TTOFC25ParseStarter项目_SWIFT18PackViewController13视图显示FSBT+49
6 UIKit 0x0000000107808a6c-[UIViewController\u setViewAppearState:isAnimating:+945
7 UIKit 0x0000000107809388-[UIViewController\u endAppearanceTransition::+197
8 UIKit 0x00000001077de28d-[UIPresentationController转换IDFinish:+834
9 UIKit 0x00000001079f5f83-[\u UICurrentContextPresentationController转换IDFinish:+42
10 UIKit 0x00000001077e1ef0 \uu 56-[UIPresentationController runTransitionForCurrentState]\u块\u调用\u 2+183
11 UIKit 0x00000001081a356c-[\u UIViewControllerTransitionContext completeTransition:][102
12 UIKit 0x00000001077daddc-[UITransitionView notifyDidCompleteTransition:][251
13 UIKit 0x00000001077daaef-[UITransitionView\u didCompleteTransition:][1539
14 UIKit 0x00000001077dd51c-[UITransitionView\u TransitiondStop:finished:][104
15 UIKit 0x00000001076edbd5-[UIViewAnimationState sendDelegateAnimationDidStop:finished:+222
16 UIKit 0x00000001076ee12a-[UIViewAnimationState animationDidStop:finished:][136
17 QuartzCore 0x0000000107392648_ZN2CA5layer23运行_动画_callbacksEPv+316
18 libdispatch.dylib 0x00000001098940cd _dispatch_client_callout+8
19 libdispatch.dylib 0x00000001098748a4_dispatch_main_queue_callback_4CF+406
20 CoreFoundation 0x00000001066abe49\uuuu CFRUNLOOP\u正在维护\u主\u调度\u队列\uuu9
21 CoreFoundation 0x000000010667137d\uuu CFRunLoopRun+2205
22 CoreFoundation 0x0000000106670884 CFRunLoopRunSpecific+420
23图形服务0x000000010bf76a6f GSEventRunModal+161
24 UIKit 0x0000000107660c68 UIApplicationMain+159
25项目Swift 0x00000001051966cf干管+111
26 libdyld.dylib 0x00000001098e068d启动+1
27°？0x0000000000000001 0x0+1
)
libc++abi.dylib:以NSException类型的未捕获异常终止
（lldb）

可能的问题

您的

collectionView

数据源是否有任何数据，如果该数据为零，

numberofitemsinssection

将返回0，并且因为您要求

collectionView

滚动到indexPath

indexPath（行：0，节：0）

并且因为单元格不在那里，它可能会崩溃

解决方案

确保数据源不是nil或始终至少返回一个单元格

使用数据重新加载collectionView后，滚动到

ViewDidDisplay

中指定的indexPath（假设调用

ViewDidDisplay

时您将拥有一些数据）

解决问题

在请求collectionView滚动到指定的indexPath之前，询问数据源是否在

indexPath（0,0）

处有单元格

if let _ = self.collectionView?.dataSource?.collectionView(self.collectionView!, cellForRowAt: IndexPath(row: 0, section: 0)) {
    self.collectionView?.scrollToItem(at: IndexPath(row: 0, section: 0), at: .top, animated: true)
}

编辑：

正如您提到的，数据来自服务器，正确的解决方案是在收到web响应后重新加载collectionView

在webservice调用的完成块中，重新加载collectionView，然后滚动到特定的索引路径

如果您正在使用alamo fire或AFNetworking，则会在主线程上调用完成块，如果在后台线程中执行完成块，请确保在重新加载和滚动之前切换到主线程：）

---

希望它有帮助：）快乐编码：）

您能尝试使用类似的：

DispatchQueue.main.async {
   self.collectionView?.scrollToItem(at: IndexPath(row: 0, section: 0), at: .top, animated: true)
}

---

这次崩溃可能有很多原因。您可以通过添加多个检查来停止此操作，就像 1.检查CollectionView数据

---

2.等待0.5秒，首先完全加载CollectionView并滚动它。

我正在进行此检查以防止应用程序崩溃。奇怪的是，当崩溃发生时，确实有一个可见的单元格，但尝试访问它时返回零

if let _ = collectionView.cellForItem(at: IndexPath(row: 0, section: 0)) {
    collectionView.scrollToItem(at: IndexPath(item: 0, section: 0), at: .top, animated: true)
}

---

尝试在self.collectionView？之前调用scrollToItem

collectionView.reloadData()

也许试试这个

let indexToScroll = 2
if let itemsCount = collectionView.dataSource?.collectionView(collectionView, numberOfItemsInSection: 0), indexToScroll < itemsCount {
    collectionView.scrollToItem(at: IndexPath(row: indexToScroll, section: 0), at: .centeredHorizontally, animated: true)
}

让索引滚动=2
如果让itemsCount=collectionView.dataSource？.collectionView（collectionView，numberOfItemsInSection:0），indexToScroll

您能提供更多详细信息吗？你能添加崩溃日志吗？主要是因为你还没有加载Co