让 UILabel 垂直方向顶端对齐的代码

原文地址：http://heidianfeng.blog.163.com/blog/static/61843456201103111444160/

让 UILabel 垂直方向顶端对齐的代码

UILabel 里放入多行文字，会发现 label 默认居中对齐，很不符合左对齐的传统习惯，下面这段 CocoaChina 版主“angellixf”分享的代码可以让 UILabel 以垂直方向顶端对齐，也就是我们常说的左对齐或右对齐

//
// VerticallyAlignedLabel.h
//

#import <Foundation/Foundation.h>

typedef enum VerticalAlignment {
VerticalAlignmentTop,
VerticalAlignmentMiddle,
VerticalAlignmentBottom,
} VerticalAlignment;

@interface VerticallyAlignedLabel : UILabel {
@private
VerticalAlignment verticalAlignment_;
}

@property (nonatomic, assign) VerticalAlignment verticalAlignment;

@end

//
// VerticallyAlignedLabel.m
//

#import "VerticallyAlignedLabel.h"

@implementation VerticallyAlignedLabel

@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