Question

我正在尝试创建一个稍后将被渲染的单元格的屏幕外版本，然后使用

[cell.label sizeToFit];

然后使用标签的新调整大小来计算这样的高度：

 float height = cell.complishLabel.bounds.size.height;
 return 50 + height;

然而，我遇到的问题是，对于身高，我总是得到0而且我不确定为什么。

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    //Make an off screen cell
    ZSSComplishTableViewCell *cell = [[ZSSComplishTableViewCell alloc] init];

    //Which section?
    if (indexPath.section == 0) {

        //Get a statement from the datasource and assign it to the label
        NSArray *todayComplishs = [[ZSSComplishStore sharedStore] todayComplishs];
        ZSSComplish *complish = todayComplishs[indexPath.row];
        cell.complishLabel.text = complish.statement;

        //Resize label to the amount of text
        [cell.complishLabel sizeToFit];

        NSLog(@"calculated height of label: %f", cell.complishLabel.frame.size.height);
        //Get height of label
        float height = cell.complishLabel.bounds.size.height;
        return 50 + height;
    } else if (indexPath.section == 1) {

        //Get a statement from the datasource and assign it to the label
        NSArray *tomorrowComplishs = [[ZSSComplishStore sharedStore] tomorrowComplishs];
        ZSSComplish *complish = tomorrowComplishs[indexPath.row];
        cell.complishLabel.text = complish.statement;

        //Resize label to the amount of text
        [cell.complishLabel sizeToFit];

        //Get height of label
        float height = cell.complishLabel.bounds.size.height;
        return 50 + height;
    }


    return 100;


}

这是ZSSComplishTableViewCell.m

- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
    if (self) {
        // Initialization code
    }
    return self;
}

- (void)awakeFromNib
{
    // Initialization code
}

- (void)setSelected:(BOOL)selected animated:(BOOL)animated
{
    [super setSelected:selected animated:animated];

    // Configure the view for the selected state
}

Answer 1

我想你什么时候

NSLog(@"calculated height of label: %f", cell.complishLabel.frame.size.height);

方法sizeToFit无法计算complishLabel帧。请尝试使用sizeThatFit:方法

another way to calculate your label height

Answer 2

这是我发现的工作：

//Set a random frame
CGRect labelFrame = CGRectMake(0, 0, 263, 1000);
//make a label with that frame
        UILabel *label = [[UILabel alloc] initWithFrame:labelFrame];
//set a preferredMaxLayoutWidth to what you want it constrained to
        label.preferredMaxLayoutWidth = 263;
//configure your label
        UIFont *font = [UIFont fontWithName:@"Gill Sans" size:18];
        label.font = font;
        label.lineBreakMode = NSLineBreakByWordWrapping;
        label.text = complish.statement;
//Set the number of lines to 0 so that it will use as many as the width and font says it needs
        label.numberOfLines = 0;

//resize the label
        [label sizeToFit];

//The height will now be adjusted to the amount of text 
        float height = label.frame.size.height;

        return 50 + height;

Answer 3

计算UILabel的高度很容易，但也很棘手。有案例需要报道。我正在使用下面的代码计算我的项目的高度。这将支持iOS 6和iOS 7或更高版本。我假设您的标签中有多行。否则，您可以调整此功能以满足您的需求。

#define SYSTEM_VERSION_LESS_THAN(v) ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedAscending)

static CGSize sizeForTextConstrainedToSize(NSString *text, UIFont *font, CGSize maxSize)
{
    if (SYSTEM_VERSION_LESS_THAN(@"7.0")) {
        CGSize size = [text sizeWithFont:font constrainedToSize:maxSize];
        return size;
    } else {
        NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
        [paragraphStyle setLineBreakMode:NSLineBreakByWordWrapping];
        NSDictionary *stringAttributes = [NSDictionary dictionaryWithObjects:@[font, paragraphStyle] forKeys:@[NSFontAttributeName, NSParagraphStyleAttributeName]];
        CGRect newRect = [text boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin attributes:stringAttributes context:nil];
        CGSize sizeAlignedToPixel = CGSizeMake(ceilf(newRect.size.width), ceilf(newRect.size.height));

        return sizeAlignedToPixel;
    }
}

对于上面的代码，您不应该计算heightForRowAtIndexPath内的高度，而是提前计算并将其存储在变量中，以确保用户滚动tableView时没有延迟。

OR：使用estimatedHeightForRowAtIndexPath，然后你可以保持你的代码在上面，但在estimatedHeightForRowAtIndexPath中返回一个近似值。

我还注意到你使用sizeToFit来获得高度，这是不对的。无论你想得到什么样的高度，你都会有一个边界。在这种情况下，它是tableView的宽度。所以你每次想要获得一个高度时都必须提供一个最大的CGSize，这是＆＃34; tableView＆＃39; s宽度x MAX_INT＆＃34;

如何在屏幕外的UITableViewCell中获取UILabel的高度？

3 个答案: