后台线程方法无法解决冻结问题

Question

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];
    }
}
}

Answer 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。

Answer 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。

Answer 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