在从主线程访问后，不得从后台线程对 > 布局引擎进行修改
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【中文标题】在从主线程访问后，不得从后台线程对 > 布局引擎进行修改【英文标题】：Modifications to the > layout engine must not be performed from a background thread after it has been accessed from the main thread 【发布时间】：2020-01-25 00:07:21 【问题描述】：我刚刚为我的 iPhone 下载了 ios 13 和新的 Xcode。我想为 iOS 13 测试我的应用程序，但是当我尝试运行我的应用程序时，它会在几秒钟后给我一个错误。错误：
由于未捕获的异常而终止应用程序 'NSInternalInconsistencyException'，原因：'修改 布局引擎不得在其后的后台线程中执行 已从主线程访问。 *** 第一次抛出调用堆栈：（0x191ea9c30 0x191bc40c8 0x192395434 0x19218eb94 0x19218eaa8 0x19218e718 0x1963e6ea8 0x191bbfaf0 0x198984384 0x19634fe54 0x19898468c 0x198997bf4 0x1988dd3e4 0x1989083a0 0x198909388 0x191bbc3c0 0x191bb4dbc 0x191bb6de8 0x191bb6b30 0x191bbcc78) libc++abi.dylib: 以未捕获的方式终止 NSException 类型的异常
在 iOS 12 及更低版本中，一切似乎都正常，我不会收到此错误。有人知道如何修复此错误以及此错误的含义吗？
下载ID：
func Download_ID()
let urlString = "https://www.instagram.com/\(self.username_String)/?__a=1"
guard let url = URL(string: urlString) else return
URLSession.shared.dataTask(with: url) data, urlResponse, error in
guard let data = data, error == nil, urlResponse != nil else
print(error)
return
do
let decoder = JSONDecoder()
let downloadedData_user = try decoder.decode(Website.self, from: data)
DispatchQueue.main.async
self.profile_img_String = downloadedData_user.graphql.user.profile_pic_url
let Veri = downloadedData_user.graphql.user.is_verified
if Veri == true
self.Verified!.isHidden = false
else
self.Verified!.isHidden = true
self.Name!.text = downloadedData_user.graphql.user.full_name
self.username!.text = self.username_String
let url = URL(string: "\(self.profile_img_String)")
self.profileImage!.kf.indicatorType = .activity
self.profileImage!.kf.setImage(
with: url,
placeholder: UIImage(named: "image-placeholder.png"),
options: [
.scaleFactor(UIScreen.main.scale),
.transition(.fade(0.4)),
.cacheOriginalImage
])
catch
print(error)
.resume()
堆栈：
Main Thread Checker: UI API called on a background thread: -[UIView setHidden:]
PID: 4437, TID: 1560742, Thread name: (none), Queue name: NSOperationQueue 0x10440d330 (QOS: UNSPECIFIED), QoS: 0
Backtrace:
4 Instagram Profile 0x00000001029c09bc $s17Instagram_Profile21History_TableViewCellC11Download_IDyyFyycfU_y10Foundation4DataVSg_So13NSURLResponseCSgs5Error_pSgtcfU_ + 1612
5 Instagram Profile 0x00000001029c10d4 $s10Foundation4DataVSgSo13NSURLResponseCSgs5Error_pSgIegggg_So6NSDataCSgAGSo7NSErrorCSgIeyByyy_TR + 284
6 CFNetwork 0x0000000195105ffc CFNetServiceBrowserSearchForServices + 95540
7 CFNetwork 0x00000001951168dc _CFHTTPMessageSetResponseProxyURL + 7680
8 Foundation 0x0000000192279c60 A99BF5C7-12EA-3700-8798-6522387A8A89 + 1170528
9 Foundation 0x000000019217b7e8 A99BF5C7-12EA-3700-8798-6522387A8A89 + 129000
10 Foundation 0x000000019227bfbc A99BF5C7-12EA-3700-8798-6522387A8A89 + 1179580
11 Foundation 0x000000019217b464 A99BF5C7-12EA-3700-8798-6522387A8A89 + 128100
12 Foundation 0x000000019227c9e8 A99BF5C7-12EA-3700-8798-6522387A8A89 + 1182184
13 Foundation 0x000000019227c4a8 A99BF5C7-12EA-3700-8798-6522387A8A89 + 1180840
14 libdispatch.dylib 0x00000001042bda48 _dispatch_block_async_invoke2 + 144
15 libdispatch.dylib 0x00000001042af2a8 _dispatch_client_callout + 20
16 libdispatch.dylib 0x00000001042b2084 _dispatch_continuation_pop + 572
17 libdispatch.dylib 0x00000001042b1468 _dispatch_async_redirect_invoke + 628
18 libdispatch.dylib 0x00000001042c0aac _dispatch_root_queue_drain + 356
19 libdispatch.dylib 0x00000001042c1418 _dispatch_worker_thread2 + 144
20 libsystem_pthread.dylib 0x0000000191bb6a60 _pthread_wqthread + 216
21 libsystem_pthread.dylib 0x0000000191bbcc78 start_wqthread + 8
2019-09-24 23:21:24.917645+0200 Instagram Profile[4437:1560742] [reports] Main Thread Checker: UI API called on a background thread: -[UIView setHidden:]
PID: 4437, TID: 1560742, Thread name: (none), Queue name: NSOperationQueue 0x10440d330 (QOS: UNSPECIFIED), QoS: 0
Backtrace:
4 Instagram Profile 0x00000001029c09bc $s17Instagram_Profile21History_TableViewCellC11Download_IDyyFyycfU_y10Foundation4DataVSg_So13NSURLResponseCSgs5Error_pSgtcfU_ + 1612
5 Instagram Profile 0x00000001029c10d4 $s10Foundation4DataVSgSo13NSURLResponseCSgs5Error_pSgIegggg_So6NSDataCSgAGSo7NSErrorCSgIeyByyy_TR + 284
6 CFNetwork 0x0000000195105ffc CFNetServiceBrowserSearchForServices + 95540
7 CFNetwork 0x00000001951168dc _CFHTTPMessageSetResponseProxyURL + 7680
8 Foundation 0x0000000192279c60 A99BF5C7-12EA-3700-8798-6522387A8A89 + 1170528
9 Foundation 0x000000019217b7e8 A99BF5C7-12EA-3700-8798-6522387A8A89 + 129000
10 Foundation 0x000000019227bfbc A99BF5C7-12EA-3700-8798-6522387A8A89 + 1179580
11 Foundation 0x000000019217b464 A99BF5C7-12EA-3700-8798-6522387A8A89 + 128100
12 Foundation 0x000000019227c9e8 A99BF5C7-12EA-3700-8798-6522387A8A89 + 1182184
13 Foundation 0x000000019227c4a8 A99BF5C7-12EA-3700-8798-6522387A8A89 + 1180840
14 libdispatch.dylib 0x00000001042bda48 _dispatch_block_async_invoke2 + 144
15 libdispatch.dylib 0x00000001042af2a8 _dispatch_client_callout + 20
16 libdispatch.dylib 0x00000001042b2084 _dispatch_continuation_pop + 572
17 libdispatch.dylib 0x00000001042b1468 _dispatch_async_redirect_invoke + 628
18 libdispatch.dylib 0x00000001042c0aac _dispatch_root_queue_drain + 356
19 libdispatch.dylib 0x00000001042c1418 _dispatch_worker_thread2 + 144
20 libsystem_pthread.dylib 0x0000000191bb6a60 _pthread_wqthread + 216
21 libsystem_pthread.dylib 0x0000000191bbcc78 start_wqthread + 8
2019-09-24 23:21:25.431565+0200 Instagram Profile[4437:1560883] WF: _userSettingsForUser mobile:
filterBlacklist = (
);
filterWhitelist = (
);
restrictWeb = 1;
useContentFilter = 0;
useContentFilterOverrides = 0;
whitelistEnabled = 0;
2019-09-24 23:21:25.431612+0200 Instagram Profile[4437:1560883] WF: _WebFilterIsActive returning: NO
2019-09-24 23:21:26.084697+0200 Instagram Profile[4437:1560883] WF: _userSettingsForUser mobile:
filterBlacklist = (
);
filterWhitelist = (
);
restrictWeb = 1;
useContentFilter = 0;
useContentFilterOverrides = 0;
whitelistEnabled = 0;
2019-09-24 23:21:26.084745+0200 Instagram Profile[4437:1560883] WF: _WebFilterIsActive returning: NO
2019-09-24 23:21:26.150637+0200 Instagram Profile[4437:1560979] NSURLConnection ordering violation: didFinishLoading to be scheduled before didReceiveResponse
2019-09-24 23:21:30.905067+0200 Instagram Profile[4437:1560742] This application is modifying the autolayout engine from a background thread after the engine was accessed from the main thread. This can lead to engine corruption and weird crashes.
Stack:(
0 Foundation 0x00000001923953a4 A99BF5C7-12EA-3700-8798-6522387A8A89 + 2331556
1 Foundation 0x000000019218eb94 A99BF5C7-12EA-3700-8798-6522387A8A89 + 207764
2 Foundation 0x000000019218eaa8 A99BF5C7-12EA-3700-8798-6522387A8A89 + 207528
3 Foundation 0x000000019218e718 A99BF5C7-12EA-3700-8798-6522387A8A89 + 206616
4 UIKitCore 0x00000001963e6ea8 EBED47E6-6BB2-3119-82CE-CC13EDCA02D6 + 15568552
5 libobjc.A.dylib 0x0000000191bbfaf0 10328337-A06E-370F-8958-6EDDA1F434DC + 6896
6 QuartzCore 0x0000000198984384 18D85F6F-635D-3A6F-BF7D-898A644FDCF5 + 1393540
7 UIKitCore 0x000000019634fe54 EBED47E6-6BB2-3119-82CE-CC13EDCA02D6 + 14949972
8 QuartzCore 0x000000019898468c 18D85F6F-635D-3A6F-BF7D-898A644FDCF5 + 1394316
9 QuartzCore 0x0000000198997bf4 18D85F6F-635D-3A6F-BF7D-898A644FDCF5 + 1473524
10 QuartzCore 0x00000001988dd3e4 18D85F6F-635D-3A6F-BF7D-898A644FDCF5 + 709604
11 QuartzCore 0x00000001989083a0 18D85F6F-635D-3A6F-BF7D-898A644FDCF5 + 885664
12 QuartzCore 0x0000000198909388 18D85F6F-635D-3A6F-BF7D-898A644FDCF5 + 889736
13 libsystem_pthread.dylib 0x0000000191bbc3c0 FEB52688-4D65-3D38-AD50-01B128A74208 + 37824
14 libsystem_pthread.dylib 0x0000000191bb4dbc FEB52688-4D65-3D38-AD50-01B128A74208 + 7612
15 libsystem_pthread.dylib 0x0000000191bb6de8 FEB52688-4D65-3D38-AD50-01B128A74208 + 15848
16 libsystem_pthread.dylib 0x0000000191bb6b30 _pthread_wqthread + 424
17 libsystem_pthread.dylib 0x0000000191bbcc78 start_wqthread + 8
)
2019-09-24 23:21:30.927369+0200 Instagram Profile[4437:1560742] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Modifications to the layout engine must not be performed from a background thread after it has been accessed from the main thread.'
*** First throw call stack:
(0x191ea9c30 0x191bc40c8 0x192395434 0x19218eb94 0x19218eaa8 0x19218e718 0x1963e6ea8 0x191bbfaf0 0x198984384 0x19634fe54 0x19898468c 0x198997bf4 0x1988dd3e4 0x1989083a0 0x198909388 0x191bbc3c0 0x191bb4dbc 0x191bb6de8 0x191bb6b30 0x191bbcc78)
libc++abi.dylib: terminating with uncaught exception of type NSException
【问题讨论】：
查看 Xcode 中的堆栈跟踪，看看你在哪里导致后台线程的布局更新。 我似乎无法弄清楚，你能帮我在哪里可以找到堆栈跟踪中后台线程的更新吗？ 从堆栈跟踪的外观来看，您正在从网络获取一些 Instagram 个人资料数据；确保此代码的完成处理程序在更新 Ui 之前分派回主队列 @Paulw11 感谢您的回复！我不确定我需要做什么来解决它。我添加了从 instagram 获取数据的功能。 面临同样的问题.. iOS 12 运行良好...... iOS 13 我遇到了问题 【参考方案1】：您的网络获取代码几乎是正确的 - 您正在重新加载主队列中的表，但没有停止活动指示器。
你只需要在闭包内移动那条线：
let downloadedData_user = try decoder.decode(Top_us.self, from: data)
self.Top_Search = downloadedData_user.users
DispatchQueue.main.async
self.tableView.reloadData()
self.Indicator.stopAnimating()
请注意，按照惯例，属性应以小写字母开头，而类应以大写字母开头。两者都应该使用驼峰式，所以Top_Search 应该是topSearch，Top_us 应该是TopUsers 和Indicator 应该是indicator。
【讨论】：
感谢您的回复，但它似乎没有奏效。我仍然遇到同样的错误！ 仔细查看堆栈跟踪，您正在表格视图单元格的Download_ID 中执行网络操作 - 这也是从后台队列更新 UI。
你找到解决办法了吗？【参考方案2】：
对于任何在确定原因时遇到问题的人，请尝试以下操作。
单击您的方案（在停止按钮旁边），然后编辑方案。
在 Run -> Diagnostics 下你必须激活 Main Thread Checker。
正如添加的断点所示，当您尝试在非主线程上更改 UI 时，您的执行现在将停止。
编辑
当没有添加断点时。可以在下面手动添加：
断点导航器 -> + -> 运行时问题断点 -> 编辑 -> 类型 -> 主线程检查器
【讨论】：
到目前为止最有用的答案在这里。谢谢你，好心的先生！ 如果我可以再投票 5 次，我会......因为这个而发现问题 我按照这些说明进行操作，但断点导航器没有显示添加的断点。它根本不显示任何断点。 哇，绝对的救命稻草 这个答案在 2022 年仍在挽救生命【参考方案3】：你应该用DispatchQueue.main.async包装处理错误
func Download_ID()
let urlString = "https://www.instagram.com/\(self.username_String)/?__a=1"
guard let url = URL(string: urlString) else return
URLSession.shared.dataTask(with: url) data, urlResponse, error in
guard let data = data, error == nil, urlResponse != nil else
// Add DispatchQueue
DispatchQueue.main.async
print(error)
return
do
let decoder = JSONDecoder()
let downloadedData_user = try decoder.decode(Website.self, from: data)
// your logic
DispatchQueue.main.async
// update or reload table in here
catch
// Add dispach_queue
DispatchQueue.main.async
print(error)
.resume()
【讨论】：
【参考方案4】：如果有人像我一样在使用 UIAlertController 时遇到此问题，请尝试将整个警报包装到 DispatchQueue.main.async 中，如下所示：
DispatchQueue.main.async
//alert:
let alert = UIAlertController(title: "Title", message: "Message", preferredStyle: .alert)
let ok = UIAlertAction(title: "Ok", style: .cancel, handler: nil)
alert.addAction(ok)
self.present(alert, animated: true, completion: nil)
【讨论】：
我的问题只出在 ios14 上，但这个解决了。谢谢！以上是关于在从主线程访问后，不得从后台线程对 > 布局引擎进行修改的主要内容，如果未能解决你的问题，请参考以下文章
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