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 
     
       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