Ios 如何优化cellForRowAtIndexPath:代码

在给一些UILabel添加字体和阴影后，我注意到当视图从堆栈中弹出时，表视图动画会滞后（像FB/Path使用的侧击）。在我添加UILabel阴影之前，侧扫是平滑的

我想我可能是把它添加到了错误的位置，所以标签属性可能被错误地添加了。请查看以下

cellforrowatinexpath:

方法：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString * cellReuseIdentifier = @"cellReuseIdentifier";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellReuseIdentifier];

    if (cell == nil)
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellReuseIdentifier];
    }

    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 2, self.view.bounds.size.width, 200)];
    imageView.image = [UIImage imageNamed:@"rest.jpg"];
    [cell.contentView addSubview:imageView];

    UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 2, 320, 30)];

    titleLabel.text = (NSString *)[[publicDataArray objectAtIndex:indexPath.row] objectForKey:@"title"];
    titleLabel.backgroundColor = [UIColor clearColor];

    titleLabel.textColor = [UIColor whiteColor];
    [titleLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:24]];
    titleLabel.layer.shadowColor = [[UIColor whiteColor] CGColor];
    titleLabel.layer.shadowOpacity = 0.7;

    [cell.contentView addSubview:titleLabel];

    UILabel *detailLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 160, cell.bounds.size.width, 30)];

    detailLabel.text = (NSString *)[[publicDataArray objectAtIndex:indexPath.row] objectForKey:@"description"];
    detailLabel.backgroundColor = [UIColor clearColor];

    detailLabel.textColor = [UIColor whiteColor];
    [detailLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:18]];
    detailLabel.layer.shadowColor = [[UIColor whiteColor] CGColor];
    detailLabel.layer.shadowOpacity = 0.7;

    [cell.contentView addSubview:detailLabel];

    cell.contentView.backgroundColor = [UIColor clearColor];


    return cell;
}

---

感谢您的帮助。

由于文本属性从未更改，请将设置它们的代码移动到

if

语句中。仅将设置标签图像和文本的代码保留在

if

语句之外。单元格被重用，因此字体等属性将保留在单元格中，即使在单元格被“回收”后也是如此。在

else

分支中，添加在单元格中查找现有标签的代码。否则，您会多次将同一标签添加到单元格中。

您总是添加新的子视图。因此，每当您滚动表格视图时，您的单元格中就会添加越来越多的内容

创建单元时创建所有子视图，然后只更新子视图设置。比如：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString * cellReuseIdentifier = @"cellReuseIdentifier";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellReuseIdentifier];

    if (cell == nil)
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellReuseIdentifier];

        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 2, self.view.bounds.size.width, 200)];
        imageView.tag = 123123;
        [cell.contentView addSubview:imageView];

        UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 2, 320, 30)];

        titleLabel.tag = 234234];
        titleLabel.backgroundColor = [UIColor clearColor];

        titleLabel.textColor = [UIColor whiteColor];
        [titleLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:24]];
        titleLabel.layer.shadowColor = [[UIColor whiteColor] CGColor];
        titleLabel.layer.shadowOpacity = 0.7;

        [cell.contentView addSubview:titleLabel];

        UILabel *detailLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 160, cell.bounds.size.width, 30)];

        detailLabel.tag = 345345];
        detailLabel.backgroundColor = [UIColor clearColor];

        detailLabel.textColor = [UIColor whiteColor];
        [detailLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:18]];
        detailLabel.layer.shadowColor = [[UIColor whiteColor] CGColor];
        detailLabel.layer.shadowOpacity = 0.7;

        [cell.contentView addSubview:detailLabel];

        cell.contentView.backgroundColor = [UIColor clearColor];
    }

    UIImageView *imageView = (UIImageView *)[cell viewWithTag:123123];
    imageView.image = [UIImage imageNamed:@"rest.jpg"];

    UILabel *titleLabel = (UILabel *)[cell viewWithTag:234234];
    titleLabel.text = (NSString *)[[publicDataArray objectAtIndex:indexPath.row] objectForKey:@"title"];

    UILabel *detailLabel = (UILabel *)[cell viewWithTag:345345];
    detailLabel.text = (NSString *)[[publicDataArray objectAtIndex:indexPath.row] objectForKey:@"description"];

    return cell;
}    

---

您可以添加子视图，即使在退出队列而不是初始化新单元之后也是如此。确保创建和添加子视图的所有代码仅在初始化单元格时执行。如果需要参考单元中的视图进行配置，请使用UITableViewCell子类

此外，阴影渲染也可能会减慢渲染速度，请添加阴影路径以提高渲染效率：

添加到您的

表格视图：cellforrowatinexpath:

方法：

...
CGPathRef shadowPath = [UIBezierPath bezierPathWithRect:detailLabel.layer.bounds].CGPath;
detailLabel.layer.shadowPath = shadowPath;
...

---

将代码替换为以下内容：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString * cellReuseIdentifier = @"cellReuseIdentifier";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellReuseIdentifier];

    if (cell == nil)
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellReuseIdentifier];


        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 2, self.view.bounds.size.width, 200)];
        imageView.image = [UIImage imageNamed:@"rest.jpg"];
        imageView.tag =1;
        [cell.contentView addSubview:imageView];

        UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 2, 320, 30)];

        titleLabel.text = (NSString *)[[publicDataArray objectAtIndex:indexPath.row] objectForKey:@"title"];
        titleLabel.backgroundColor = [UIColor clearColor];
        titleLabel.tag = 2;
        titleLabel.textColor = [UIColor whiteColor];
        [titleLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:24]];
        titleLabel.layer.shadowColor = [[UIColor whiteColor] CGColor];
        titleLabel.layer.shadowOpacity = 0.7;

        [cell.contentView addSubview:titleLabel];

        UILabel *detailLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 160, cell.bounds.size.width, 30)];
        detailLabel.tag = 3;
        detailLabel.text = (NSString *)[[publicDataArray objectAtIndex:indexPath.row] objectForKey:@"description"];
        detailLabel.backgroundColor = [UIColor clearColor];

        detailLabel.textColor = [UIColor whiteColor];
        [detailLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:18]];
        detailLabel.layer.shadowColor = [[UIColor whiteColor] CGColor];
        detailLabel.layer.shadowOpacity = 0.7;


    }

    UIImageView *tempImgView = (UIImageView *)[cell viewWithTag:1];
    tempImgView.image = [UIImage imageNamed:@""];// Here you can set any image by reusing imageview without allocating again and again

    UILabel *tempLabel;

    tempLabel = (UILabel *)[cell viewWithTag:2];
    tempLabel.text = @"";// Here you can access your title label and can set its properties without allocating again

    tempLabel = (UILabel *)[cell viewWithTag:3];
    tempLabel.text = @"";// Here you can access your detailLabel label and can set its properties without allocating again


     [cell.contentView addSubview:detailLabel];

    cell.contentView.backgroundColor = [UIColor clearColor];


    return cell;
}

---

您需要使用类创建自定义表视图单元格。这段代码你添加了很多标签然后阴影显示不正确。 代码是这样的

（UITableViewCell*）tableView:（UITableView*）tableView cellForRowAtIndexPath:（NSIndexPath*）indexPath { 静态NSString*cellReuseIdentifier=@“cellReuseIdentifier”； UITableCustomViewCell*单元格=[tableView dequeueReusableCellWithIdentifier:cellReuseIdentifier]

if (cell == nil)
{
    cell = [[UITableCustomViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellReuseIdentifier];
}

cell.imageView.image = [UIImage imageNamed:@"rest.jpg"];

cell.titleLabel.text = (NSString *)[[publicDataArray objectAtIndex:indexPath.row] objectForKey:@"title"];

cell.detailLabel.text = (NSString *)[[publicDataArray objectAtIndex:indexPath.row] objectForKey:@"description"];

return cell;

---

}这篇来自Twitter工程的文章为您提供了一个很好的概述：

基本上，您希望避免使用子视图，而是直接使用Quartz绘制内容。这是提高性能所能做的最好的事情。另外：避免透明度！在工具中，还可以使用核心动画工具并激活“颜色混合层”，以查看组成透明视图的位置：

---

标题标签.layer.shouldRasterize=是；detailLabel.layer.shouldRasterize=YES@阿马尔：谢谢！这就不同了，但也要检查@Wain！！凉的但是你应该按照@Wainyep的建议优化你的单元格创建代码。我也改变了。再次感谢