自定义UILabel的对齐方式

在iOS中默认的UILabel中的文字在竖直方向上只能居中对齐，自定义UILabel，实现了居上对齐，居中对齐，居下对齐。具体如下：

    //  
    //  myUILabel.h  
    //    
    //  
    //  Created by yexiaozi_007 on 3/4/13.  
    //  Copyright (c) 2013 yexiaozi_007. All rights reserved.  
    //  
      
    #import <UIKit/UIKit.h>  
    typedef enum  
    {  
        VerticalAlignmentTop = 0, // default  
        VerticalAlignmentMiddle,  
        VerticalAlignmentBottom,  
    } VerticalAlignment;  
    @interface myUILabel : UILabel  
    {  
    @private  
    VerticalAlignment _verticalAlignment;  
    }  
      
    @property (nonatomic) VerticalAlignment verticalAlignment;  
      
    @end  

    //  
    //  myUILabel.m  
    //    
    //  
    //  Created by yexiaozi_007 on 3/4/13.  
    //  Copyright (c) 2013 yexiaozi_007. All rights reserved.  
    //  
      
    #import "myUILabel.h"  
      
    @implementation myUILabel  
    @synthesize verticalAlignment = verticalAlignment_;  
      
    - (id)initWithFrame:(CGRect)frame {  
        if (self = [super initWithFrame:frame]) {  
            self.verticalAlignment = VerticalAlignmentMiddle;  
        }  
        return self;  
    }  
      
    - (void)setVerticalAlignment:(VerticalAlignment)verticalAlignment {  
        verticalAlignment_ = verticalAlignment;  
        [self setNeedsDisplay];  
    }  
      
    - (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines {  
        CGRect textRect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines];  
        switch (self.verticalAlignment) {  
            case VerticalAlignmentTop:  
                textRect.origin.y = bounds.origin.y;  
                break;  
            case VerticalAlignmentBottom:  
                textRect.origin.y = bounds.origin.y + bounds.size.height - textRect.size.height;  
                break;  
            case VerticalAlignmentMiddle:  
                // Fall through.  
            default:  
                textRect.origin.y = bounds.origin.y + (bounds.size.height - textRect.size.height) / 2.0;  
        }  
        return textRect;  
    }  
      
    -(void)drawTextInRect:(CGRect)requestedRect {  
        CGRect actualRect = [self textRectForBounds:requestedRect limitedToNumberOfLines:self.numberOfLines];  
        [super drawTextInRect:actualRect];  
    }  
      
      
    @end  

在使用时：

    lbl_mylabel = [[myUILabel alloc] initWithFrame:CGRectMake(20, 50, 150, 600)];
    UIColor *color = [UIColor colorWithPatternImage:[UIImage imageNamed:@"halfTransparent.png"]];//使用半透明图片作为label的背景色
    lbl_mylabel.backgroundColor = color;
    lbl_mylabel.textAlignment = UITextAlignmentLeft;
    lbl_mylabel.textColor = UIColor.whiteColor;
    lbl_mylabel.lineBreakMode = UILineBreakModeWordWrap;
    lbl_mylabel.numberOfLines = 0;
    [lbl_mylabel setVerticalAlignment:VerticalAlignmentTop];
    [self addSubview:lbl_mylabel];

转载:http://blog.csdn.net/yexiaozi_007/article/details/8636522