这可能是一个非常直接的应用程序,但我是 Objective-C(来自 Java)的新手,整个内存管理和“EXC_BAD_ACCESS”错误让我心碎。
我有一个带有核心数据的普通 NavigationController iPhone 应用程序。在 AppDelegate 中创建 NSManagedObjectContext 并将其传递给 RootViewController。直接从主线程中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,因此一旦应用程序启动,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];
}
问题是这行不通。在 DataManager 中,首先需要检索设置,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;
}
我猜指向 ManagedObjectContext 的指针是错误的,因为在不同的线程和内存池中运行。那么如果这是问题,你如何创建这样的应用程序),我如何获得对他线程的原始 ManagedObjectContext 格式的引用?
[编辑] 我也尝试使用
iDomsAppDelegate *appDelegate = (iDomsAppDelegate *)[[UIApplication sharedApplication] delegate];
DataManager *data = [[DataManager alloc] initWithContext:appDelegate.managedObjectContext];
在 doUpdateData 中(正如其他帖子所暗示的那样),但这给出了相同的结果