你仍然可以使用sizeWithFont。但是，在iOS >= 7.0中，如果字符串包含开头和结尾空格或结束行\n，则会导致崩溃。

在使用文本之前修剪文本

label.text = [label.text stringByTrimmingCharactersInSet:
             [NSCharacterSet whitespaceAndNewlineCharacterSet]];

这也适用于sizeWithAttributes和[label sizeToFit]。

此外，当你有nsstringdrawingtextstorage消息发送到deallocated实例在ios7.0设备它处理这个。

- (CGSize) sizeWithMyFont:(UIFont *)fontToUse
{
    if ([self respondsToSelector:@selector(sizeWithAttributes:)])
    {
        NSDictionary* attribs = @{NSFontAttributeName:fontToUse};
        return ([self sizeWithAttributes:attribs]);
    }
    return ([self sizeWithFont:fontToUse]);
}

在Xamarin接受的答案将是(使用sizeWithAttributes和UITextAttributeFont):

        UIStringAttributes attributes = new UIStringAttributes
        { 
            Font = UIFont.SystemFontOfSize(17) 
        }; 
        var size = text.GetSizeUsingAttributes(attributes);

改用sizeWithAttributes:，它现在接受一个NSDictionary。传入key UITextAttributeFont和你的字体对象，如下所示:

CGRect rawRect = {};
rawRect.size = [string sizeWithAttributes: @{
    NSFontAttributeName: [UIFont systemFontOfSize:17.0f],
}];

// Values are fractional -- you should take the ceil to get equivalent values
CGSize adjustedSize = CGRectIntegral(rawRect).size;

// max size constraint
CGSize maximumLabelSize = CGSizeMake(184, FLT_MAX)

// font
UIFont *font = [UIFont fontWithName:TRADE_GOTHIC_REGULAR size:20.0f];

// set paragraph style
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
paragraphStyle.lineBreakMode = NSLineBreakByWordWrapping;

// dictionary of attributes
NSDictionary *attributes = @{NSFontAttributeName:font,
                             NSParagraphStyleAttributeName: paragraphStyle.copy};

CGRect textRect = [string boundingRectWithSize: maximumLabelSize
                                     options:NSStringDrawingUsesLineFragmentOrigin
                                  attributes:attributes
                                     context:nil];

CGSize expectedLabelSize = CGSizeMake(ceil(textRect.size.width), ceil(textRect.size.height));

如果有人需要的话，这里有一个单一的对等物:

/// <summary>
/// Measures the height of the string for the given width.
/// </summary>
/// <param name="text">The text.</param>
/// <param name="font">The font.</param>
/// <param name="width">The width.</param>
/// <param name="padding">The padding.</param>
/// <returns></returns>
public static float MeasureStringHeightForWidth(this string text, UIFont font, float width, float padding = 20)
{
    NSAttributedString attributedString = new NSAttributedString(text, new UIStringAttributes() { Font = font });
    RectangleF rect = attributedString.GetBoundingRect(new SizeF(width, float.MaxValue), NSStringDrawingOptions.UsesLineFragmentOrigin, null);
    return rect.Height + padding;
}

可以这样使用:

public override float GetHeightForRow(UITableView tableView, NSIndexPath indexPath)
{
    //Elements is a string array
    return Elements[indexPath.Row].MeasureStringHeightForWidth(UIFont.SystemFontOfSize(UIFont.LabelFontSize), tableView.Frame.Size.Width - 15 - 30 - 15);
}