这可能是一个非常直接的应用程序,但我是Objective-C的新手(来自Java),整个内存管理和“EXC_BAD_ACCESS”错误让我心碎。
我有一个普通的NavigationController iPhone App,带有Core Data。在AppDelegate中创建NSManagedObjectContext并将其传递给RootViewController。直接从主线程查找视图以填充表格,这似乎工作正常。
该应用程序是某种RSS类型的阅读器,因此只要应用程序启动,我就会触发一个线程来获取新数据并更新视图:
-(void)updateData:(id)sender {
UIActivityIndicatorView *activityIndicator =
[[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(0, 0, 20, 20)];
[activityIndicator startAnimating];
UIBarButtonItem *activityItem =
[[UIBarButtonItem alloc] initWithCustomView:activityIndicator];
[activityIndicator release];
self.navigationItem.leftBarButtonItem = activityItem;
[activityItem release];
// Start thread to update the data
[NSThread detachNewThreadSelector:@selector(doUpdateData) toTarget:self withObject:nil];
}
-(void)doUpdateData{
NSLog(@"Update data Thread (in 5 sec.)");
[NSThread sleepForTimeInterval:5];
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
DataManager *data = [[DataManager alloc] initWithContext:managedObjectContext];
[data updateData];
[data release];
data=nil;
[self performSelectorOnMainThread:@selector(finishUpdateData) withObject:nil waitUntilDone:NO];
[pool release];
}
-(void)finishUpdateData{
self.navigationItem.leftBarButtonItem = updateBttn;
DataManager *data = [[DataManager alloc] initWithContext:managedObjectContext];
objects = [data getArticles];
[data release];
data=nil;
NSLog(@"Amount of records after update: %d", [objects count]);
[self.tableView reloadData];
}
问题是这不起作用。在DataManager中,需要检索第一个设置,并且一旦创建了NSEntityDescription,我就会得到“EXC_BAD_ACCESS”:
- (NSFetchedResultsController *)fetchedResultsController {
// Set up the fetched results controller if needed.
if (fetchedResultsController == nil) {
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Setting" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"key" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
[fetchRequest setFetchLimit:1];
.
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:nil];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
[aFetchedResultsController release];
[fetchRequest release];
[sortDescriptor release];
[sortDescriptors release];
}
return fetchedResultsController;
}
我认为指向ManagedObjectContext的指针是错误的,因为在不同的线程和内存池中运行。那么如果这是一个问题,你如何创建这样的应用程序),我如何获得他对线程的原始ManagedObjectContext格式的引用?
[编辑] 我也尝试过使用
iDomsAppDelegate *appDelegate = (iDomsAppDelegate *)[[UIApplication sharedApplication] delegate];
DataManager *data = [[DataManager alloc] initWithContext:appDelegate.managedObjectContext];
在doUpdateData中的(如其他帖子所示),但结果相同