Swift环境下实现UILabel居上 居中 居下对齐

首先在Xcode中新建.h文件，将下面代码复制进去

//

//  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

再新建一个.m文件。拷入下面代码

//

//  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

假设这是你导入的第一个.m文件Xcode会提示你要不要创建Bridging-Header，选Ok

在新创建的Bridging-Header文件中拷入下方代码

#import "myUILabel.h"

然后打开你的StoryBoard，点选你想要更改对齐方式的Label，将其Class改为myUILabel。示意图例如以下

然后右键拖动Label或者按住Control键左键拖动连线到Label所在的父View的Class中生成Outlet，假设之前已经连线好。则改完Custom Class后，将连线生成代码中的UILabel改为myUILabel，示意图例如以下

然后就能够调用该label的类方法

label.verticalAlignment = VerticalAlignmentBottom

按上方代码能够实现居下对其，居中 居上 分别将代码中的Bottom改为Middle和Top。默觉得居上