前言：

没有理由不去努力.png

正文：
想实现UILabel居上对齐，居中对齐，居下对齐，如下效果：

效果图.png

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：

创建：MYLabel 继承与UILabel

在MYLabel.h中完成

在MYLabel.h中完成

//
//  MYLabel.h
//  LabelDemo
//
//  Created by wangergang on 2016/12/7.
//  Copyright ? 2016年 MYCompangName. All rights reserved.
//

#import <UIKit/UIKit.h>

typedef enum {
    VerticalAlignmentTop = 0, //default
    VerticalAlignmentMiddle,
    VerticalAlignmentBottom,

} VerticalAlignment;

@interface MYLabel : UILabel {

@private
    VerticalAlignment _verticalAlignment;
}

@property (nonatomic) VerticalAlignment verticalAlignment;

@end

在MYLabel.m中完成

在MYLabel.m中完成

//
//  MYLabel.m
//  LabelDemo
//
//  Created by wangergang on 2016/12/7.
//  Copyright ? 2016年 MYCompangName. All rights reserved.
//

#import "MYLabel.h"

@implementation MYLabel

@synthesize verticalAlignment = verticalAlignment_;

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.verticalAlignment = VerticalAlignmentMiddle;
    }
    return self;
}

- (void)setVerticalAlignment:(VerticalAlignment)verticalAlignment {
    verticalAlignment_ = verticalAlignment;
    [self setNeedsLayout];
}


- (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

使用：首先记得引入头文件

import "MYLabel.h"

- (void)viewDidLoad {
    [super viewDidLoad];

    [self setupLabel];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)setupLabel {
    //居上对齐
    MYLabel *topLabel = [[MYLabel alloc] initWithFrame:CGRectMake(20, 275, 350, 200)];

    topLabel.text = @"剧终了、剧终了、剧终了、剧终了、剧终了、剧终了、剧终了、";
    topLabel.backgroundColor = [UIColor cyanColor];
    topLabel.textAlignment = NSTextAlignmentLeft;
    topLabel.textColor = [UIColor blueColor];
    topLabel.lineBreakMode = NSLineBreakByCharWrapping;
    topLabel.numberOfLines = 0;
    [topLabel setVerticalAlignment:VerticalAlignmentMiddle];
    [self.view addSubview:topLabel];


    //居中对齐
    MYLabel *middleLabel = [[MYLabel alloc] initWithFrame:CGRectMake(20, 500, 350, 200)];

    middleLabel.text = @"向下看、向下看、向下看、向下看、向下看、向下看、向下看、向下看、";
    middleLabel.backgroundColor = [UIColor cyanColor];
    middleLabel.textAlignment = NSTextAlignmentLeft;
    middleLabel.textColor = [UIColor blueColor];
    middleLabel.lineBreakMode = NSLineBreakByCharWrapping;
    middleLabel.numberOfLines = 0;
    [middleLabel setVerticalAlignment:VerticalAlignmentBottom];
    [self.view addSubview:middleLabel];

    //居下对齐
    MYLabel *bottomLabel = [[MYLabel alloc] initWithFrame:CGRectMake(20, 50, 350, 200)];

    bottomLabel.text = @"看我居上对齐了啊、你看看对不对的啊、看来是对的";
    bottomLabel.backgroundColor = [UIColor cyanColor];
    bottomLabel.textAlignment = NSTextAlignmentLeft;
    bottomLabel.textColor = [UIColor blueColor];
    bottomLabel.lineBreakMode = NSLineBreakByCharWrapping;
    bottomLabel.numberOfLines = 0;
    [bottomLabel setVerticalAlignment:VerticalAlignmentTop];
    [self.view addSubview:bottomLabel];
}

其效果图如上图：就不再上传了

Demo位置github位置