后台线程方法无法解决冻结问题
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【中文标题】后台线程方法无法解决冻结问题【英文标题】：Background thread method not solving freezing issue 【发布时间】：2015-05-21 04:08:15 【问题描述】：我有我的应用程序冻结问题，所以我使用 Instruments 查找问题，发现问题与 CoreData 保存和获取有关。我已经尝试过后台 coredata 方法（父子，通知），但我的问题还没有解决。我还提到了http://martiancraft.com/blog/2015/03/core-data-stack/，但不知道这个方法是如何在我的应用程序中实现的。
仪器日志： https://www.dropbox.com/s/agjtw1wqubsgwew/Instruments9.trace.zip?dl=0
保存到数据库
-(void)updateThreadEntityWithSyncDetails:(NSMutableDictionary *)inDictionary
NSString *loginUser=[[NSUserDefaults standardUserDefaults] valueForKey:@"currentUser"];
AppDelegate *sharedDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [sharedDelegate managedObjectContext];
// NSManagedObjectContext *writerContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
// [writerContext setPersistentStoreCoordinator:[sharedDelegate persistentStoreCoordinator]];
// create main thread MOC
// context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
// context.parentContext = writerContext;
// NSManagedObjectContext *contextforThread = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
// contextforThread.parentContext = context;
// [contextforThread performBlock:^
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setReturnsObjectsAsFaults:NO];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"ThreadInfo"
inManagedObjectContext:context];
[fetchRequest setEntity:entity];
NSPredicate *userPredicate = [NSPredicate predicateWithFormat:@"userEmail == %@",loginUser];
NSPredicate *threadPredicate = [NSPredicate predicateWithFormat:@"threadID == %@",[inDictionary valueForKey:@"thread"]];
NSPredicate *compoundPredicate = [NSCompoundPredicate andPredicateWithSubpredicates: @[userPredicate, threadPredicate]];
[fetchRequest setPredicate:compoundPredicate];
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:nil];
for (ThreadInfo *threadInfo in fetchedObjects)
if([[inDictionary allKeys] containsObject:@"userEmail"])
if([inDictionary valueForKey:@"userEmail"]!=[NSNull null])
threadInfo.userEmail=[inDictionary valueForKey:@"userEmail"];
if([[inDictionary allKeys] containsObject:@"badgeValue"])
if([inDictionary valueForKey:@"badgeValue"]!=[NSNull null])
threadInfo.badgeValue=[inDictionary valueForKey:@"badgeValue"];
if([[inDictionary allKeys] containsObject:@"choice4Percentage"])
if([inDictionary valueForKey:@"choice4Percentage"]!=[NSNull null])
threadInfo.choice4Percentage=[inDictionary valueForKey:@"choice4Percentage"];
if([[inDictionary allKeys] containsObject:@"choice5Percentage"])
if([inDictionary valueForKey:@"choice5Percentage"]!=[NSNull null])
threadInfo.choice5Percentage=[inDictionary valueForKey:@"choice5Percentage"];
NSError *error;
if(![context save:&error])
NSLog(@"Child error : %@",error);
// [context performBlock:^
// NSError *error;
// if(![context save:&error])
// NSLog(@"%@",error);
//
// ];
// ];
获取
-(ThreadInfo *)retrieveSolicitationInfoForThreadID:(NSString*)inThreadID;
NSString *loginUser=[[NSUserDefaults standardUserDefaults] valueForKey:@"currentUser"];
AppDelegate *sharedDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [sharedDelegate managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setReturnsObjectsAsFaults:NO];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"ThreadInfo"
inManagedObjectContext:context];
[fetchRequest setEntity:entity];
NSPredicate *userPredicate = [NSPredicate predicateWithFormat:@"userEmail == %@",loginUser];
NSPredicate *threadPredicate = [NSPredicate predicateWithFormat:@"threadID == %@",inThreadID];
\
NSPredicate *compoundPredicate = [NSCompoundPredicate andPredicateWithSubpredicates: @[userPredicate, threadPredicate]];
[fetchRequest setPredicate:compoundPredicate];
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:nil];
if(fetchedObjects.count!=0)
ThreadInfo *threadInfo=[fetchedObjects objectAtIndex:0];
return threadInfo;
return nil;
同步
-(void)updateSolicitationWithSyncDetails:(NSDictionary *)inDictionary
NSMutableDictionary *paramDict=[NSMutableDictionary dictionaryWithDictionary:inDictionary];
NSString *userEmail=[[NSUserDefaults standardUserDefaults] valueForKey:@"currentUser"];
[paramDict setObject:[NSNumber numberWithBool:NO] forKey:@"isSystemMessage"];
[paramDict setObject:userEmail forKey:@"userEmail"];
if([[inDictionary allKeys] containsObject:@"owned"])
BOOL isDuplicate=[[IXDataBaseManager sharedNetworkDataManager] checkForExistenceOfThreadDetailsForSolicitationID:[inDictionary objectForKey:@"solicitation"]];// FETCH
if(!isDuplicate)
int randomIndex=[[IXNetworkDataManager sharedNetworkDataManager] getIndexForColorImageForTab:@"OUT"];
[paramDict setObject:message forKey:@"threadDescription"];
[paramDict setObject:[NSNumber numberWithInt:randomIndex] forKey:@"colorCode"];
BOOL isDuplicateVal=[[IXDataBaseManager sharedNetworkDataManager] checkForExistenceOfSolicitationID:[inDictionary objectForKey:@"solicitation"]];// FETCH
[paramDict setObject:message forKey:@"threadDescription"];
ThreadInfo *threadInfo=[[IXDataBaseManager sharedNetworkDataManager] retrieveSolicitationInfoForThreadID:[inDictionary objectForKey:@"solicitation"]];
[paramDict setObject:threadInfo.threadID forKey:@"thread"];
[[IXDataBaseManager sharedNetworkDataManager] updateThreadEntityWithSyncDetails:paramDict];
【问题讨论】：
【参考方案1】：首先，感谢您立即提供代码 sn-ps 和跟踪。这很有帮助。
所以，查看跟踪和代码。
-updateThreadEntityWithSyncDetails: 在主线程上被调用，33% 的时间都花在了那里。不好。
您将 nil 传递给 error: 永远不要这样做。始终传递错误指针并检查调用结果以查看是否有错误。
这个条件可以更简洁：
if([[inDictionary allKeys] containsObject:@"userEmail"])
if([inDictionary valueForKey:@"userEmail"]!=[NSNull null])
threadInfo.userEmail=[inDictionary valueForKey:@"userEmail"];
考虑：
if (inDictionary[@"userEmail"] != nil && inDictionary[@"userEmail"] != [NSNull null])
threadInfo.userEmail = inDictionary[@"userEmail"];
更容易阅读。
此方法的重写将使工作脱离主线程：
- (void)updateThreadEntityWithSyncDetails:(NSMutableDictionary*)inDictionary
NSString *loginUser = [[NSUserDefaults standardUserDefaults] valueForKey:@"currentUser"];
AppDelegate *sharedDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
[context setParentContext:[sharedDelegate managedObjectContext]];
[context performBlock:^
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"ThreadInfo"];
[fetchRequest setReturnsObjectsAsFaults:NO];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:@"userEmail == %@ && threadID == %@",loginUser, inDictionary[@"thread"]];
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:nil];
for (ThreadInfo *threadInfo in fetchedObjects)
if (inDictionary[@"userEmail"] != nil && inDictionary[@"userEmail"] != [NSNull null])
threadInfo.userEmail = inDictionary[@"userEmail"];
if (inDictionary[@"badgeValue"] != nil && inDictionary[@"badgeValue"] != [NSNull null])
threadInfo.badgeValue = inDictionary[@"badgeValue"];
if (inDictionary[@"choice4Percentage"] != nil && inDictionary[@"choice4Percentage"] != [NSNull null])
threadInfo.choice4Percentage = inDictionary[@"choice4Percentage"];
if (inDictionary[@"choice5Percentage"] != nil && inDictionary[@"choice5Percentage"] != [NSNull null])
threadInfo.choice5Percentage = inDictionary[@"choice5Percentage"];
NSError *error = nil;
if (![context save:&error])
NSLog(@"Child error : %@",error);
];
但是它可能仍会阻塞主线程，因为我猜测大部分 CPU 时间都用于执行此提取。获取速度很慢。您在该提取中有两个字符串比较。那很糟糕，应该纠正。如果 ThreadID 不是字符串，则反转获取。否则，这只是糟糕的数据模型设计，除了修复该提取之外没有太多帮助。
你的另一个慢点是-checkForExistenceOfThreadDetailsForThreadID:。您没有发布该方法，但我怀疑这是同一个问题，您的 fetch 花费了您大量的时间并且它在主队列中。
总体上这个设计很差，需要返工。您正在比较数据存储中的字符串，这是检索数据的最慢方法之一。对于似乎不需要在主线程上的事情，您也在主线程上。
记住黄金法则，如果数据没有被用户操作，那么操作不能在主队列上。没有例外。
【讨论】：
【参考方案2】：您是否尝试过使用单独的上下文进行操作，并在保存后将其与 mainContext 合并？
例如
NSManagedObjectContext * localContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
[localContext setPersistentStoreCoordinator:[[self managedObjectContext] persistentStoreCoordinator]];
导入完成后保存localContext
NSError * error = nil;
if (![[self localContext] save:&error])
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
这会将您的数据写入 PersistentStore。
现在您的 mainContext 需要了解 PersistentStore 中的更改。这是通过观察通知来完成的。
例如
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(didSaveNotification:)
name:NSManagedObjectContextDidSaveNotification
object:nil];
这是对通知做出反应的方法：
- (void)didSaveNotification:(NSNotification *)notification
// NSLog(@"%s %@\n",__PRETTY_FUNCTION__,[notification userInfo]);
NSManagedObjectContext * mainContext = [self managedObjectContext];
void (^mergeChanges)(void)=^
[mainContext mergeChangesFromContextDidSaveNotification:notification];
;
if([NSThread isMainThread])
mergeChanges();
else
dispatch_sync(dispatch_get_main_queue(), mergeChanges);
使用不同的 NSManagedContext 处理同一个 PersistentStore 比使用单个 NSManagedContext 更线程安全。
【讨论】：
评论不用于扩展讨论；这个对话是moved to chat。【参考方案3】： //Your Parent context init
- (NSManagedObjectContext *)managedObjectContext
if (_managedObjectContext != nil)
return _managedObjectContext;
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil)
_managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
[_managedObjectContext setUndoManager:nil];
return _managedObjectContext;
- (NSManagedObjectContext *)childManagedObjectContext
if (_childManagedObjectContext != nil)
return _childManagedObjectContext;
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil)
_childManagedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
[_childManagedObjectContext setPersistentStoreCoordinator:coordinator];
[_childManagedObjectContext setUndoManager:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_mocDidSaveNotification:) name:NSManagedObjectContextDidSaveNotification object:nil];
return _childManagedObjectContext;
- (void)_mocDidSaveNotification:(NSNotification *)notification
NSManagedObjectContext *savedContext = [notification object];
// ignore change notifications for the main MOC
if (_managedObjectContext == savedContext)
return;
if (_managedObjectContext.persistentStoreCoordinator != savedContext.persistentStoreCoordinator)
// that's another database
return;
dispatch_sync(dispatch_get_main_queue(), ^
[_managedObjectContext mergeChangesFromContextDidSaveNotification:notification];
);
//父子上下文的使用方式
[UIAppDelegate.childManagedObjectContext performBlock:^
for (int i=0; i<count; i++)
//Fill Database and save it in child context first for each entry and save it in child context
[UIAppDelegate.childManagedObjectContext save:nil];
dispatch_sync(dispatch_get_main_queue(), ^
//Finally when u have inserted all entries save in the parent context
[UIAppDelegate.managedObjectContext save:nil];
);
]
//你的代码很庞大，很难理解逻辑，但如果你还没有尝试过这种方式，那就试试吧
【讨论】：
可能是使用两个上下文的问题，如果我使用三个上下文会怎样？ workContext-Maincontext-ChildContext 。你知道如何实现这个吗？ 我已经尝试过这种方法，但应用程序仍然冻结。在保存之前有一些获取，这也会导致问题，您可以查看我的分析器日志。我如何有效地使用两者？ floriankugler.com/2013/04/02/the-concurrent-core-data-stack 是一篇很好的文章，其中有解释。另外我已经编辑了代码，请检查 在你的代码中为什么要两次保存mainObjectcontext？如果我们已经在使用通知，那么为什么我们需要 [UIAppDelegate.managedObjectContext save:nil]; ? 对不起，你不需要通知部分。你可以删除它以上是关于后台线程方法无法解决冻结问题的主要内容，如果未能解决你的问题，请参考以下文章
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