UITableView 单元格中图像重叠的问题

Question

我在 coredata sqlite Painter 和 Picture 中有 2 个表。具有一对多的关系。 在表“图片”中，我有字符串属性 pictureName。我将图片（153）存储在磁盘上 这段代码我将 imageView 添加到单元格中：

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    self.tableView.transform = CGAffineTransformMakeRotation( -M_PI/2 );
    self.tableView.showsHorizontalScrollIndicator = NO;
    self.tableView.showsVerticalScrollIndicator = NO;
    [self.tableView setFrame:CGRectMake(0, 156, 1024, 449)];
}

- (void)viewDidUnload
{
    [self setTableView:nil];
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return YES;
}
#pragma mark - UITableView Delegate Methods
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return [[fetchedResultsController fetchedObjects] count];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    Painter *painter = [[fetchedResultsController fetchedObjects] objectAtIndex:section];
    //NSLog(@"%i", [painter.pictures count]);
    return [painter.pictures count];
    //return 152;
}
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {
    Painter *painter = [[fetchedResultsController fetchedObjects] objectAtIndex:indexPath.section];
    Picture *picture = [[painter.pictures allObjects] objectAtIndex:indexPath.row];
    UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:[NSString stringWithFormat:@"%@s.jpg", picture.imgName]]];
    NSLog(@"add image %@s.jpg to sector:%i row:%i", picture.imgName, indexPath.section, indexPath.row);
    imageView.transform = CGAffineTransformMakeRotation( M_PI/2 );
    [cell addSubview:imageView];
    [imageView release];
}

- (UITableViewCell *)tableView:(UITableView *)tableViewCurrent cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableViewCurrent dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }

    // Configure the cell.
    [self configureCell:cell atIndexPath:indexPath];
    return cell;
}
- (CGFloat)tableView:(UITableView *)aTableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    return 300.0;
}

- (void)tableView:(UITableView *)aTableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{ 
}


#pragma mark - Fetched results controller

- (NSFetchedResultsController *)fetchedResultsController
{
    if (fetchedResultsController != nil) {
        return fetchedResultsController;
    }

    // Create the fetch request for the entity.
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Painter" inManagedObjectContext:managedObjectContext];
    [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:@"name" ascending:NO];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects: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:managedObjectContext sectionNameKeyPath:nil cacheName:@"Main"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    [aFetchedResultsController release];
    [fetchRequest release];
    [sortDescriptor release];
    [sortDescriptors release];

    return fetchedResultsController;
}

` 我有一个问题：每个单元格里都有很多照片 http://ge.tt/9QX5lc4?c （选择查看按钮） 为什么？

Answer 1

细胞正在被重复利用。每次配置单元格时，都会添加图像视图作为子视图。随着时间的推移，这些积累并提供您所看到的效果。您应该检查图像视图是否已存在并向其分配图像，或者首先清理单元格，然后使用图像对其进行设置。

Answer 2

以下代码是导致您出现问题的原因：

static NSString *CellIdentifier = @"Cell";

UITableViewCell *cell = [tableViewCurrent dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
// Configure the cell.
[self configureCell:cell atIndexPath:indexPath];
return cell;

您基本上是在第一次创建单元格时对其进行缓存，并在后续调用 tableView:cellForRowAtIndexPath: 时重新使用它（如果您不想）要缓存此内容，那么您每次都需要创建一个新单元格。

UITableViewCell *cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
// Configure the cell.
[self configureCell:cell atIndexPath:indexPath];
return cell;

这应该可以解决你的问题。有更复杂的方法来处理单元格，例如缓存它并直接操作其子视图，而不是每次都重新创建它。当您继续编写代码时需要记住一些事情。