ios – UITableView cellForRowAtIndexPath为每一行调用多次

如果我有一个包含4行的UITableView,那么当我导航到该视图时,不应该调用4次cellForRowAtIndexPath方法吗？我发现它被多次调用,例如如果有4行,当我深入到UITable视图时会被调用8次,然后当我导航回到同一个UITableView时被调用12次.

我只是误解了这种方法的工作原理吗？我认为应该为显示的每一行调用一次(没有涉及滚动,因为表格视图的内容很容易适合我的iPad屏幕).

我应该注意到UITableView包含在iPad上的UISplitViewController的MasterViewController中.

编辑：我得到的真正问题是以下代码的应用方式不一致：

if (selectednavItem.folder.isAssignedToUser != [NSNumber numberWithInt:1]) 
        {
            NSLog(@"%@",cell.textLabel.text);
            cell.selectionStyle = UITableViewCellSelectionStyleNone;
            cell.userInteractionEnabled = NO;
            cell.textLabel.enabled = NO;
            cell.detailTextLabel.text = @"Access not granted";
            cell.detailTextLabel.enabled = NO;
        }

当我第一次“深入”到我的导航堆栈的特定级别时,事情就像他们应该的那样工作.但是后来如果我向上或向下导航,我发现各行被错误地处理,即当它们应该被启用时它们最终会被禁用.这导致我提出了一个断点和一些日志代码来试图找出发生了什么.我发现上面的代码被调用的次数比行数多 – 而且我记录的cell.textLabel.text值没有意义 – 同一行的值被多次记录 – 而其他行则没有记录在一起.

编辑：根据要求提供一些代码：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static Nsstring *CellIdentifier = @"FolderCell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    [self configureCell:cell atIndexPath:indexPath];
    return cell;
}


- (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:@"NavItem" inManagedobjectContext:self.managedobjectContext];
    [fetchRequest setEntity:entity];

    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];

    // Edit the sort keys as appropriate.
    NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"sortOrder" ascending:YES];
    NSSortDescriptor *sortDescriptor2 = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES selector:@selector(localizedCaseInsensitiveCompare:)];
    NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDescriptor1,sortDescriptor2,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:self.
        managedobjectContext sectionNameKeyPath:nil cacheName:@"Master"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&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();
    }

    return __fetchedResultsController;
}   

- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
    NSManagedobject *managedobject = [self.fetchedResultsController objectAtIndexPath:indexPath];
    NavItem *selectednavItem = (NavItem *)managedobject;
    cell.textLabel.text = [[managedobject valueForKey:@"name"] description];
    cell.detailTextLabel.text = @"";

    if (selectednavItem.folder != nil) {
        cell.imageView.image = [UIImage imageNamed:@"Folder.png"];


        //NSLog(@"%@",selectednavItem.folder.isAssignedToUser);

        if (selectednavItem.folder.isAssignedToUser != [NSNumber numberWithInt:1]) 
        {
            NSLog(@"%@",cell.textLabel.text);
            cell.selectionStyle = UITableViewCellSelectionStyleNone;
            cell.userInteractionEnabled = NO;
            cell.textLabel.enabled = NO;
            cell.detailTextLabel.text = @"Access not granted";
            cell.detailTextLabel.enabled = NO;
        }
    }
    else if (selectednavItem.document != nil) {
        cell.detailTextLabel.text  = [[selectednavItem.document valueForKey:@"itemDescription"] description];

        if ([[selectednavItem.document.fileName pathExtension] isEqualToString:@"pdf"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"pdf.png"];
        }
        else if ([[selectednavItem.document.fileName pathExtension] isEqualToString:@"doc"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"docx"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"Word-32x32.png"];
        }
        else if ([[selectednavItem.document.fileName pathExtension] isEqualToString:@"xls"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"xlsx"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"Excel-32x32.png"];
        }
        else if ([[selectednavItem.document.fileName pathExtension] isEqualToString:@"ppt"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"pps"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"Powerpoint-32x32.png"];
        }
        else if ([[selectednavItem.document.fileName pathExtension] isEqualToString:@"mp3"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"wav"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"65-note.png"];
        }
        else if ([[selectednavItem.document.fileName pathExtension] isEqualToString:@"mp4"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"mov"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"46-movie-2.png"];
        }
        else if ([[selectednavItem.document.fileName pathExtension] isEqualToString:@"ibooks"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"ibooks-icon.png"];
        }
        else if ([[selectednavItem.document.fileName pathExtension] isEqualToString:@"png"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"bmp"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"jpg"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"jpeg"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"tif"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"tiff"] || [[selectednavItem.document.fileName pathExtension] isEqualToString:@"gif"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"41-picture-frame.png"];
        }
        else 
        {
            cell.imageView.image = [UIImage imageNamed:@"179-notepad.png"];
        }


    }
    else if (selectednavItem.attachment != nil) {
        cell.detailTextLabel.text  = [[selectednavItem.attachment valueForKey:@"itemDescription"] description];

        if ([[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"pdf"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"pdf.png"];
        }
        else if ([[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"doc"] || [[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"docx"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"Word-32x32.png"];
        }
        else if ([[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"xls"] || [[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"xlsx"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"Excel-32x32.png"];
        }
        else if ([[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"ppt"] || [[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"pps"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"Powerpoint-32x32.png"];
        }
        else if ([[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"mp3"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"65-note.png"];
        }
        else if ([[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"mp4"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"46-movie-2.png"];
        }
        else if ([[selectednavItem.document.fileName pathExtension] isEqualToString:@"ibooks"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"ibooks-icon.png"];
        }
        else if ([[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"png"] || [[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"bmp"] || [[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"jpg"] || [[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"jpeg"] || [[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"tif"] || [[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"tiff"] || [[selectednavItem.attachment.fileName pathExtension] isEqualToString:@"gif"]) 
        {
            cell.imageView.image = [UIImage imageNamed:@"41-picture-frame.png"];
        }
        else 
        {
            cell.imageView.image = [UIImage imageNamed:@"179-notepad.png"];
        }
    }

}