NSFetchedResultsController委托分配了太多UITableViewCells

in the Apple documentation .

我遇到的问题是,当我大量插入新的核心数据实体时。这会导致NSFetchedResultsController委托为每个实体分配(并插入)一个新的单元格,但这样做时不会回收UITableViewCells(即。, dequeueReusableCellWithIdentifier: 总是返回null)。这意味着可能要分配100个UITableViewCells,这可能会导致内存问题。有人知道修复或解决方法吗?谢谢。

在UITableViewController子类中,我有标准的NSFetchedResultsControllerDelegate方法。我相信这和苹果的例子是一样的。

-(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:UITableViewRowAnimationTop];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationBottom];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationBottom];
            // Reloading the section inserts a new row and ensures that titles are updated appropriately.
            [tableView reloadSections:[NSIndexSet indexSetWithIndex:newIndexPath.section] withRowAnimation:UITableViewRowAnimationTop];
            break;
    }
}

-(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:UITableViewRowAnimationTop];
            break;

        case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationBottom];
            break;
    }
}

-(void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    // The fetch controller has sent all current change notifications, so tell the table view to process all updates.
    [self.tableView endUpdates];
}

同样在UITableViewController子类中,我有以下用于获取给定indexPath的单元格:

-(void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {
    Waypoint *waypoint = [self.fetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = [waypoint comment];
}

-(UITableViewCell *)tableView:(UITableView *)aTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {    
    static NSString *CellIdentifier = @"WaypointCell"; // matches identifier in XIB

    UITableViewCell *cell = [aTableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        NSLog(@"new cell");
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];      
        cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
    } else {
        NSLog(@"recycled cell");    
    }

    [self configureCell:cell atIndexPath:indexPath];

    return cell;
}

在 tableView:cellForRowAtIndexPath:

[self.tableView endUpdates] 调用时,系统开始创建UITableViewCells并将其插入UITableView。在调试器控制台中,输出“new cell”被打印多次(可以是100的数字),我相信每创建一个新实体就打印一次。只有在加载tableview(如果它没有因为内存问题而崩溃)并开始滚动之后,我才能在控制台中看到“recycled cell”输出。