Question

我想为我的tableview单元格添加自定义背景和选定的背景图像。目前似乎当细胞被重复使用时，背景图像被搞砸，顶部细胞将使用底部细胞图像等。

在这种情况下我是否错误地重复使用了单元格？

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

    static NSString *CellIdentifier = @"Cell";

    UIImageView *linkAvailableImageView = nil;
    UIView *backgroundView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, tableView.bounds.size.width, 44)];
    UIView *selectedBackgroundView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, tableView.bounds.size.width, 44)];

    UIImageView *backgroundImage = [[UIImageView alloc] initWithFrame:CGRectMake(10, 0, tableView.bounds.size.width-20, 44)];
    UIImageView *selectedBackgroundImage = [[UIImageView alloc] initWithFrame:CGRectMake(10, 0, tableView.bounds.size.width-20, 44)];


    // Asset
    Asset *asset = nil;
    asset = (Asset *)[items objectAtIndex:indexPath.row];

    int count = [items count];

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

        if (indexPath.row == 0 && count > 1) {
            backgroundImage.frame = CGRectMake(10, 0, tableView.bounds.size.width-20, 45);
            backgroundImage.image = [[UIImage imageNamed:@"MDACCellBackgroundTop.png"] stretchableImageWithLeftCapWidth:5 topCapHeight:10];
            selectedBackgroundImage.frame = CGRectMake(10, -1, tableView.bounds.size.width-20, 45);
            selectedBackgroundImage.image = [[UIImage imageNamed:@"MDACCellBackgroundSelectedTop.png"] stretchableImageWithLeftCapWidth:5 topCapHeight:10];
        } else if (indexPath.row == count-1 && count > 1) {
            backgroundImage.image = [[UIImage imageNamed:@"MDACCellBackgroundBottom.png"] stretchableImageWithLeftCapWidth:5 topCapHeight:10];
            selectedBackgroundImage.image = [[UIImage imageNamed:@"MDACCellBackgroundSelectedBottom.png"] stretchableImageWithLeftCapWidth:5 topCapHeight:10];
        } else if (indexPath.row == 0 && count == 1) {
            backgroundImage.frame = CGRectMake(10, -1, tableView.bounds.size.width-20, 45);
            backgroundImage.image = [[UIImage imageNamed:@"MDACCellBackgroundSingle.png"] stretchableImageWithLeftCapWidth:5 topCapHeight:10];
            selectedBackgroundImage.image = [[UIImage imageNamed:@"MDACCellBackgroundSelectedSingle.png"] stretchableImageWithLeftCapWidth:5 topCapHeight:10];
        } else {
            backgroundImage.image = [[UIImage imageNamed:@"MDACCellBackgroundMiddle.png"] stretchableImageWithLeftCapWidth:1 topCapHeight:10];
            selectedBackgroundImage.image = [[UIImage imageNamed:@"MDACCellBackgroundSelectedMiddle.png"] stretchableImageWithLeftCapWidth:1 topCapHeight:10];
        }//end

        backgroundImage.autoresizingMask = UIViewAutoresizingFlexibleWidth;
        [backgroundView addSubview:backgroundImage];
        [backgroundImage release];

        selectedBackgroundImage.autoresizingMask = UIViewAutoresizingFlexibleWidth;
        [selectedBackgroundView addSubview:selectedBackgroundImage];
        [selectedBackgroundImage release];

        cell.backgroundView = backgroundView;
        [backgroundView release];

        cell.selectedBackgroundView = selectedBackgroundView;
        [selectedBackgroundView release];

        linkAvailableImageView = [[[UIImageView alloc] initWithFrame:CGRectMake(cell.contentView.bounds.size.width-39, 9, 24, 24)] autorelease];
        linkAvailableImageView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin;
        linkAvailableImageView.image = [UIImage imageNamed:@"MDACLinkArrow.png"];
        linkAvailableImageView.tag = 3;
        [cell.contentView addSubview:linkAvailableImageView];

    } else {
        linkAvailableImageView = (UIImageView *)[cell.contentView viewWithTag:3];
    }

    // Get asset
    cell.textLabel.opaque = NO;
    cell.textLabel.text = asset.name;
    cell.textLabel.font = [UIFont boldSystemFontOfSize:17];
    cell.textLabel.backgroundColor = [UIColor colorWithWhite:94./255. alpha:1];
    cell.textLabel.textColor = [UIColor whiteColor];
    cell.textLabel.shadowColor = [UIColor colorWithWhite:0 alpha:0.6];
    cell.textLabel.shadowOffset = CGSizeMake(0, -1);

    // Set the kind of disclosure indicator
    if ([asset.children intValue] > 0) {
        //cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
    } else {
        cell.accessoryType = UITableViewCellAccessoryNone;
    }//end

    // Lazy Load the image
    if (!asset.appIcon) {

        // Download icon
        [self startIconDownload:asset forIndexPath:indexPath];

        // if a download is deferred or in progress, return a placeholder image
        cell.imageView.image = [UIImage imageNamed:@"default-icon.png"]; 

    } else {
        cell.imageView.image = asset.appIcon;
    }//end

    return cell;

}//end

Answer 1

很抱歉，但该代码存在很多问题：您正在泄漏UIView和UIImageView个对象，并且整个单元格的重用都是错误的，因此您的问题就会出现。

您应该只在if (cell == nil)部分设置一个新单元格（包含观看次数），并且不要忘记release / autorelease您的观看次数。然后，在该块之外，相应地配置您的单元格（设置其内容）。

我强烈建议您查看Apple的一些示例项目！

Answer 2

这里的问题是，无论表视图中的位置如何，您都使用相同的单元格标识符。

因此，您最初根据indexPath.row和count创建单元格，但是将这些单元格与@“Cell”标识符相关联。因此，当您向下滚动dequeueReusableCellWithIdentifier时，将返回为列表开头配置的单元格（indexPath.row == 0＆amp;＆amp; count＆gt; 1），并将其用于列表的末尾。

您需要确保单元格标识符反映单元格开头的代码== nill if block，以便您只重用已为您正在创建的表格中的位置配置的单元格。

正如Eiko指出的那样，你也在泄漏你的UIView和UIImageView对象。您可以将它们粘贴在if块中，明确释放它们或者只是让它们自动释放。

UITableViewCell backgroundView在它不应该被重用时被重用

2 个答案: