我有一个相当基本的应用程序，它从一个视图控制器获取输入并保存它，允许用户在单独的表视图控制器上查看数据。保存的数据不过是几个字符串和一个图像。一切都工作得很好，直到突然之间，我的图像不再出现在TableViewController中，直到应用程序重置为止。
我的表格视图设置了正确的部分数量和正确的单元格数量，其中显示的数据应该是应有的，唯一的例外是图像。
这是我的“保存到CoreData”代码：
- (IBAction)saveTarget:(id)sender {
//Only save if there is an image other than the stock photo
if (self.transfer.targetImage) {
//Grab the main ManagedObjectContext from the AppDelegate
sTCAppDelegate *appDelegate =[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context =[appDelegate managedObjectContext];
//Get the Target model from CoreData
[self setTarget:[NSEntityDescription insertNewObjectForEntityForName:@"TargetData" inManagedObjectContext:context]];
//Save the strings from the child view controller
self.target.weaponData = self.transfer.weaponData;
self.target.bulletType = self.transfer.bulletType;
self.target.stanceType = self.transfer.stanceType;
self.target.distanceData = self.transfer.distanceData;
self.target.targetNotes = self.transfer.targetNotes;
self.target.sightType = self.transfer.sightType;
self.target.scoreData = self.transfer.scoreData;
//Save the image from the child view controller
self.target.targetImage = self.transfer.targetImage;
//Save the range data from the preset values
self.target.rangeName = self.name;
self.target.rangeStreet = self.street;
self.target.rangeCity = self.city;
self.target.rangeState = self.state;
//Set a date property to use for organizing by most recently saved
NSDate *date = [NSDate date];
NSDate *dateMod = [self dateAtBeginningOfDayForDate:date];
self.target.timeStamp = dateMod;
//Save a more user-friendly date string
self.target.formattedTimeStamp = [self.dateFormatter stringFromDate:dateMod];
//Save to context
NSError *error = nil;
if ( ![context save:&error] ){
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
//Pop to main menu
[self.navigationController popToRootViewControllerAnimated:YES];
//set images back to nil for next time AddTarget is opened
self.target.targetImage = nil;
NSLog(@"Data Saved");
}
//Return alert if user has not entered a photo
else{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"We're Sorry!" message:@"You must enter at least a photo to save target data." delegate:nil cancelButtonTitle:@"Okay" otherButtonTitles:nil];
[alert show];
}
}
这是我的“从CoreData代码中检索”：
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
NSLog(@"number of sections:%lu",(unsigned long)[[self.fetchedResultsController sections] count]);
return [[self.fetchedResultsController sections] count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
NSLog(@"%lu", (unsigned long)[sectionInfo numberOfObjects]);
return [sectionInfo numberOfObjects];
}
-(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section{
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
return [[[sectionInfo objects] objectAtIndex:0] formattedTimeStamp];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
NSLog(@"Ran Cell Configure");
[self configureCell:cell atIndexPath:indexPath];
// Configure the cell...
return cell;
}
-(void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath{
TargetData *target = [self.fetchedResultsController objectAtIndexPath:indexPath];
UIImage *image = [self resizeImage:[UIImage imageWithData:target.targetImage] toWidth:50 andHeight:50];
cell.imageView.image = image;
cell.textLabel.text = [NSString stringWithFormat:@"%@", target.scoreData];
cell.detailTextLabel.text = target.weaponData;
}
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
sTCAppDelegate *appDelegate =[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context =[appDelegate managedObjectContext];
[context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
NSError *error;
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();
}
}
}
#pragma mark- Fetched Objects Delegate
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController != nil)
{
return _fetchedResultsController;
}
sTCAppDelegate *appDelegate =[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context =[appDelegate managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"TargetData" inManagedObjectContext:context];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:0];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timeStamp" ascending:NO];
NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedRequestsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:@"timeStamp" cacheName:nil];
aFetchedRequestsController.delegate = self;
self.fetchedResultsController = aFetchedRequestsController;
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error])
{
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return _fetchedResultsController;
}
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex]
withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath]
atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
}
答案 0 :(得分：0)
这行代码有效地将图像设置为nil在对象上。
//set images back to nil for next time AddTarget is opened
self.target.targetImage = nil;
也许你应该这样做
self.target = nil;