有人问到怎样正确地对齐UILabel的文字。他们需要UILabel容纳多行文本，但也需要调整文本，他们遇到的问题是单行文本在垂直方向总是居中对齐。 

 

在apple论坛上: 
http://discussions.apple.com/thread.jspa?threadID=1759957有人提供的UILabel子类可以解决这个问题：

此子类如下：

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    // Label2.h
    // (c) 2009 Ivan Misuno, www.cuberoom.biz<br>
   
    #import <UIKit/UIKit.h>

    typedef enum
    {
        VerticalAlignmentTop = 0, // default
        VerticalAlignmentMiddle,
        VerticalAlignmentBottom,
    } VerticalAlignment;
     
    @interface Label2 : UILabel
    {
    @private
        VerticalAlignment _verticalAlignment;
    }
   
    @property (nonatomic) VerticalAlignment verticalAlignment;
     
    @end
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    // Label2.mm
    // (c) 2009 Ivan Misuno, www.cuberoom.biz
     
    #import "Label2.h"
     
    @implementation Label2
   
    -(id)initWithFrame:(CGRect)frame
    {
        self = [super initWithFrame:frame];
        if (!self) return nil;
     
        _verticalAlignment = VerticalAlignmentTop;
        return self;
    }
   
    -(void)dealloc
    {
        [super dealloc];
    }
   
    -(VerticalAlignment) verticalAlignment
    {
        return _verticalAlignment;
    }
   
    -(void) setVerticalAlignment:(VerticalAlignment)value
    {
        _verticalAlignment = value;
       [self setNeedsDisplay];
    }
   
    // align text block according to vertical alignment settings
    -(CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines
    {
        CGRect rect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines];
        CGRect result;
        switch(_verticalAlignment)
        {
        case VerticalAlignmentTop:
            result = CGRectMake(bounds.origin.x, bounds.origin.y, rect.size.width, rect.size.height);
            break;
     
        case VerticalAlignmentMiddle:
            result = CGRectMake(bounds.origin.x, bounds.origin.y +
                (bounds.size.height - rect.size.height) / 2, rect.size.width,  rect.size.height);
            break;
     
        case VerticalAlignmentBottom:
            result = CGRectMake(bounds.origin.x, bounds.origin.y +
                 (bounds.size.height - rect.size.height), rect.size.width,  rect.size.height);
            break;

        default:
            result = bounds;
            break;
        }
        return result;
    }
 
    -(void)drawTextInRect:(CGRect)rect
    {
        CGRect r = [self textRectForBounds:rect limitedToNumberOfLines:self.numberOfLines];
        [super drawTextInRect:r];
    }
   
    @end

 

你可以在使用UILabel的地方使用Label2。可以通过将setVerticalAlignment设为VerticalAlignmentTop, VerticalAlignmentMiddle, 或 VerticalAlignmentBottom的方法将文本对齐在顶部，中间或底部。十分方便！

 

原文见：UILabel Subclass – Align The Text How You Want!