使用动态高度的多行标签可能需要额外的信息来正确设置大小。你可以使用sizeWithAttributes with UIFont和NSParagraphStyle来指定字体和换行模式。

你可以像这样定义段落样式并使用NSDictionary:

// set paragraph style
NSMutableParagraphStyle *style = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
[style setLineBreakMode:NSLineBreakByWordWrapping];
// make dictionary of attributes with paragraph style
NSDictionary *sizeAttributes        = @{NSFontAttributeName:myLabel.font, NSParagraphStyleAttributeName: style};
// get the CGSize
CGSize adjustedSize = CGSizeMake(label.frame.size.width, CGFLOAT_MAX);

// alternatively you can also get a CGRect to determine height
CGRect rect = [myLabel.text boundingRectWithSize:adjustedSize
                                                         options:NSStringDrawingUsesLineFragmentOrigin
                                                      attributes:sizeAttributes
                                                         context:nil];

你可以使用CGSize ' adjuststedsize '或CGRect作为矩形。size.height属性如果你在寻找高度。

更多关于NSParagraphStyle的信息请访问:https://developer.apple.com/library/mac/documentation/cocoa/reference/applicationkit/classes/NSParagraphStyle_Class/Reference/Reference.html

基于@bitsand，这是一个新方法，我刚刚添加到我的NSString+Extras类别:

- (CGRect) boundingRectWithFont:(UIFont *) font constrainedToSize:(CGSize) constraintSize lineBreakMode:(NSLineBreakMode) lineBreakMode;
{
    // set paragraph style
    NSMutableParagraphStyle *style = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
    [style setLineBreakMode:lineBreakMode];

    // make dictionary of attributes with paragraph style
    NSDictionary *sizeAttributes = @{NSFontAttributeName:font, NSParagraphStyleAttributeName: style};

    CGRect frame = [self boundingRectWithSize:constraintSize options:NSStringDrawingUsesLineFragmentOrigin attributes:sizeAttributes context:nil];

    /*
    // OLD
    CGSize stringSize = [self sizeWithFont:font
                              constrainedToSize:constraintSize
                                  lineBreakMode:lineBreakMode];
    // OLD
    */

    return frame;
}

我只是使用结果帧的大小。

boundingRectWithSize:options:attributes:context:

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);
}