有两种方法可以解决这个问题。一种是

[mylabel setNumberOfLines:0];
[mylabel sizeToFit];

但是第二种方法对于这种方法更可靠，

 CGSize sizeToFit = [label.text sizeWithFont:label.font constrainedToSize:maxSize lineBreakMode:label.lineBreakMode];
 [mylabel setFrame:CGRectMake(mylabel.frame.origin.x, mylabel.frame.origin.y, sizeToFit.width, sizeToFit.height)];

输入“\n”不是一件好事，但如果您知道将要显示的数据的约束和大小，则可以，如果文本长度大于标签的大小，则可能会很好，但无法扩展。第二种方式最终根据要显示的文本的大小设置框架。

不要大惊小怪

@interface MFTopAlignedLabel : UILabel

@end


@implementation MFTopAlignedLabel

- (void)drawTextInRect:(CGRect) rect
{
    NSAttributedString *attributedText = [[NSAttributedString alloc]     initWithString:self.text attributes:@{NSFontAttributeName:self.font}];
    rect.size.height = [attributedText boundingRectWithSize:rect.size
                                            options:NSStringDrawingUsesLineFragmentOrigin
                                            context:nil].size.height;
    if (self.numberOfLines != 0) {
        rect.size.height = MIN(rect.size.height, self.numberOfLines * self.font.lineHeight);
    }
    [super drawTextInRect:rect];
}

@end

没有混乱，没有Objective-c，没有大惊小怪，只有Swift 3:

class VerticalTopAlignLabel: UILabel {

    override func drawText(in rect:CGRect) {
        guard let labelText = text else {  return super.drawText(in: rect) }

        let attributedText = NSAttributedString(string: labelText, attributes: [NSFontAttributeName: font])
        var newRect = rect
        newRect.size.height = attributedText.boundingRect(with: rect.size, options: .usesLineFragmentOrigin, context: nil).size.height

        if numberOfLines != 0 {
            newRect.size.height = min(newRect.size.height, CGFloat(numberOfLines) * font.lineHeight)
        }

        super.drawText(in: newRect)
    }

}

雨燕4.2

class VerticalTopAlignLabel: UILabel {

    override func drawText(in rect:CGRect) {
        guard let labelText = text else {  return super.drawText(in: rect) }

        let attributedText = NSAttributedString(string: labelText, attributes: [NSAttributedString.Key.font: font])
        var newRect = rect
        newRect.size.height = attributedText.boundingRect(with: rect.size, options: .usesLineFragmentOrigin, context: nil).size.height

        if numberOfLines != 0 {
            newRect.size.height = min(newRect.size.height, CGFloat(numberOfLines) * font.lineHeight)
        }

        super.drawText(in: newRect)
    }

}

试试这个！！太手动了，但对我来说很完美。

[labelName setText:@"This is just a demo"];

NSMutableString *yourString1= @"This is just a demo";


// breaking string
labelName.lineBreakMode=UILineBreakModeTailTruncation;
labelName.numberOfLines = 3;


CGSize maximumLabelSize1 = CGSizeMake(276,37); // Your Maximum text size

CGSize expectedLabelSize1 = [yourString1 sizeWithFont:labelName.font
                                    constrainedToSize:maximumLabelSize1
                                        lineBreakMode:labelName.lineBreakMode];

[labelName setText:yourString1];


CGRect newFrame1 = labelName.frame;
if (expectedLabelSize1.height>=10)
{
    newFrame1.size.height = expectedLabelSize1.height;
}

labelName.frame = newFrame1;

一种更快（更脏）的方法是将UILabel的换行模式设置为“Clip”并添加固定数量的换行符。

myLabel.lineBreakMode = UILineBreakModeClip;
myLabel.text = [displayString stringByAppendingString:"\n\n\n\n"];

这种解决方案不适用于所有人——特别是，如果您仍然希望在字符串末尾显示“…”，如果它超过了您要显示的行数，则需要使用较长的代码段之一——但在很多情况下，这将满足您的需要。

在发布的所有其他解决方案的基础上，我创建了一个简单的小UILabel子类，在设置其对齐属性时将为您处理垂直对齐。这还将在方向更改时更新标签，将高度约束到文本，并将标签的宽度保持在其原始大小。

.h

@interface VAlignLabel : UILabel
@property (nonatomic, assign) WBZVerticalAlignment alignment;
@end


.m

 -(void)setAlignment:(WBZVerticalAlignment)alignment{

    _alignment = alignment;

    CGSize s = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(self.frame.size.width, 9999) lineBreakMode:NSLineBreakByWordWrapping];

    switch (_alignment)
    {
        case wbzLabelAlignmentVerticallyTop:
            self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y, self.frame.size.width, s.height);
            break;
        case wbzLabelAlignmentVerticallyMiddle:
            self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y + (self.frame.size.height - s.height)/2, self.frame.size.width, s.height);
            break;
        case wbzLabelAlignmentVerticallyBottom:
            self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y + (self.frame.size.height - s.height), self.frame.size.width, s.height);
            break;
        default:
            break;
    }
}

-(void)layoutSubviews{
    [self setAlignment:self.alignment];
}

我很长一段时间都在纠结这个问题，我想分享我的解决方案。

这将为您提供一个UILabel，它将自动将文本缩小到0.5个刻度，并将文本垂直居中。故事板/IB中也提供了这些选项。

[labelObject setMinimumScaleFactor:0.5];
[labelObject setBaselineAdjustment:UIBaselineAdjustmentAlignCenters];