iphone - UITableView在离开框架时在单元格上随机滴答

Question

我有一个UITableView，您只能在其中勾选4个单元格。如果我勾选一定数量的单元格，然后向上或向下滚动，它将勾选随机单元格。我不了解其背后的逻辑，因为我用于滴答的唯一方法是DidSelectRowAtIndex，它不会被执行(我在其中放置了一个断点以进行检查)。我真的不知道是什么原因造成的，但是这里是cellForRowAtIndex:

- (UITableViewCell *) tableView: (UITableView *) tableView
          cellForRowAtIndexPath: (NSIndexPath *) indexPath
{

        static NSString *cellName = @"PrefsTableViewCell";

        UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:
                                 cellName];
        if (cell == nil)
        {
                cell = [[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellName] autorelease];
        }

        NSUInteger row = [indexPath row];
        Drink *drink = [drinks objectAtIndex:row];

        cell.textLabel.text = drink.name;
        cell.detailTextLabel.text = [NSString stringWithFormat:@"%d", drink.caffeine];
        [[cell imageView] setImage:drink.image];

        return cell;
}

我感觉这与它有关，但我真的无法分辨。

这是滚动之前的样子:

当我向上滚动到顶部时，将发生以下情况:

我没有点击那个前一个。如果我上下滚动，可能会被取消勾选，而另一个会被勾选。

可能很重要，所以这里是didSelectRowAtIndexPath方法:

- (void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
        UITableViewCell *cell = [tableView cellForRowAtIndexPath: indexPath];

        NSLog(@"TESTING");

        if ((cell.accessoryType == UITableViewCellAccessoryNone) && [[DataContainerSingleton theDataContainerSingleton].favourites count] < 4)
        {
                cell.accessoryType = UITableViewCellAccessoryCheckmark;

                [[DataContainerSingleton theDataContainerSingleton].favourites addObject:[drinks objectAtIndex:indexPath.row]];
                NSLog(@"CHECKED %d", [[DataContainerSingleton theDataContainerSingleton].favourites count]);
        }
        else if (cell.accessoryType == UITableViewCellAccessoryCheckmark)
        {
            for (int i = 0; i < [[DataContainerSingleton theDataContainerSingleton].favourites count]; i++)
            {
                NSString *drinkName = [[drinks objectAtIndex:indexPath.row] name];
                NSString *favName = [[[DataContainerSingleton theDataContainerSingleton].favourites objectAtIndex:i] name];

                if ([drinkName isEqualToString: favName])
                {
                    cell.accessoryType = UITableViewCellAccessoryNone;
                    [[DataContainerSingleton theDataContainerSingleton].favourites removeObjectAtIndex:i];
                    NSLog(@"UNCHECKED %d", [[DataContainerSingleton theDataContainerSingleton].favourites count]);
                }
            }

        }
}

Answer 1

您没有保存已勾选的项目。您应该将索引保存在数组中，并在cellForRowAtIndexPath:中设置对勾。就像是-

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [tableView deselectRowAtIndexPath:indexPath animated:YES];

        if(![self.tickedIndexPaths containsObject:indexPath]) //tickedIndexPaths is an array
            [self.tickedIndexPaths addObject:indexPath];
        else
            [self.tickedIndexPaths removeObject:indexPath];
}

然后-

- (UITableViewCell *) tableView: (UITableView *) tableView
          cellForRowAtIndexPath: (NSIndexPath *) indexPath
{

        static NSString *cellName = @"PrefsTableViewCell";

        UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:
                                 cellName];
        if (cell == nil)
        {
                cell = [[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellName] autorelease];
        }

        NSUInteger row = [indexPath row];
        Drink *drink = [drinks objectAtIndex:row];

        cell.textLabel.text = drink.name;
        cell.detailTextLabel.text = [NSString stringWithFormat:@"%d", drink.caffeine];
        [[cell imageView] setImage:drink.image];

        if([self.tickedIndexPaths containsObject:indexPath])
        {
              cell.accessoryType = UITableViewCellAccessoryCheckmark;
        }
        else
        {
              cell.accessoryType = UITableViewCellAccessoryNone;
        }

        return cell;
}

请记住，由于单元的重用，最后的else块非常重要。