我在 UIViewController 中有一个 UITableView ，这样我就可以在表格下方有一个 UILabel 。这样做时，我在添加编辑/完成按钮时遇到了困难。我不能做传统的方式，所以我不得不使用以下想法做一个工作：
1）在viewdidload左上角创建编辑按钮：
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemEdit target:self action:@selector(editbutton)];
2）创建代码，以便在单击编辑按钮时，表格视图变为可编辑，并将标题更改为完成。然后点击完成后，它会回到说编辑。
-(IBAction)editbutton{
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(donebutton)];
[tableView setEditing:YES animated:YES];
}
-(IBAction)donebutton{
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemEdit target:self action:@selector(editbutton)];
[tableView setEditing:NO animated:YES];
}
这部分一切正常。我只是为了完整性把它放进去。单击编辑按钮时，表格视图变为可编辑的，我可以单击完成并恢复正常。我的问题是单击删除按钮（单击一行旁边的红色减号按钮后）不会删除该行。我尝试了以下代码：
注意：1)context 在 .h 文件中被声明为：@property (nonatomic, retain) NSManagedObjectContext *context; 并在.m文件中合成。2）我在.h文件中声明了@property（非原子，保留）NSFetchedResultsController *fetchedResultsController，然后在.m文件中声明了@synthesize fetchedResultsController = _fetchedResultsController
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
// Delete the managed object for the given index path
[context deleteObject:[_fetchedResultsController objectAtIndexPath:indexPath]];
// Save the context.
NSError *error = nil;
if (![context save:&error]) {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
*/
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
}
}
编辑：
好的，我找到了一些解决方案。我使用以下代码删除了我的核心数据：
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
// Delete the managed object for the given index path
NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
[context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
// Save the context.
NSError *error = nil;
if (![context save:&error]) {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
*/
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
[self fetchedresults];
[self.tableView reloadData];
}
}
我的新问题是当我单击删除时。该行被删除，但仍保留在那里，空白行上的红色减号按钮。我仍然可以单击该行（通常编辑数据），但没有要加载的数据。
编辑2：
我忘了添加，为了让它工作，我添加了这个：
- (NSFetchedResultsController *)fetchedResultsController{
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
// Set up the fetched results controller.
// Create the fetch request for the entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Record" inManagedObjectContext:context];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:20];
// Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"activity" ascending:YES];
NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
// Edit the section name key path and cache name if appropriate.
// nil for section name key path means "no sections".
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:nil cacheName:@"Master"];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error]) {
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return _fetchedResultsController;
}
编辑 3：
这就是获取的结果的作用：
- (void)fetchedresults {
NSManagedObjectContext *moc = [self context];
NSEntityDescription *entityDescription = [NSEntityDescription
entityForName:@"Record" inManagedObjectContext:moc];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDescription];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc]
initWithKey:@"activity" ascending:YES];
[request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];
NSError *error = nil;
NSArray *array = [moc executeFetchRequest:request error:&error];
if (array == nil)
{
// Deal with error...
}
float tot = [[array valueForKeyPath:@"@sum.cpdhours"] floatValue];
totalhours.text = [NSString stringWithFormat:@"%.1f", tot];
}