iOS UILabel设置居上对齐，居中对齐，居下对齐

在iOS中默认的UILabel中的文字在竖直方向上只能居中对齐，博主参考国外网站，从UILabel继承了一个新类，实现了居上对齐，居中对齐，居下对齐。具体如下：

[cpp] view
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//

// 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

[cpp] view
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//

// 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：

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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];