???????系統中的UILabel對齊方式只有左、中、右對齊方式，有時候希望文本內容上部、中間和底部對齊，所以下面自定義一個繼承UILabel的類來實現上部、中間和底部對齊。先來看一下.h文件：

.h 文件

typedef NS_ENUM (NSInteger ,VerticalAlignment){
VerticalAlignmentTop = 0,  //上居中
VerticalAlignmentMiddle, //中居中
VerticalAlignmentBottom //低居中
};

@interface VerticalLabel : UILabel

@property (nonatomic,assign)VerticalAlignment verticalAlignment;

@end

.m文件

@implementation VerticalLabel

-(instancetype)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 = self.bounds.origin.y;
        break;

        case VerticalAlignmentMiddle:
        break;

        case VerticalAlignmentBottom:
            textRect.origin.y = bounds.origin.y +       bounds.size.height - textRect.size.height;
        break;

        default:
            textRect.origin.y = bounds.origin.y + (bounds.size.height - textRect.size.height) / 2.0;
        break;
}
    return textRect;
}
-(void)drawTextInRect:(CGRect)rect{
    CGRect actualRect = [self textRectForBounds:rect limitedToNumberOfLines:self.numberOfLines];
    [super drawTextInRect:actualRect];
}

使用此類:請看下面的使用的例子

VerticalLabel *textLabel = [[VerticalLabel alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
textLabel.numberOfLines = 1;
textLabel.font = [UIFont systemFontOfSize:18];
textLabel.text = @"哈哈哈哈哈";
textLabel.textColor = [UIColor redColor];
textLabel.backgroundColor = [UIColor greenColor ];
textLabel.verticalAlignment = VerticalAlignmentTop;
textLabel.textAlignment = NSTextAlignmentRight;
[self.view addSubview:textLabel];

搭配系統的屬性textAlignment,可以組成左上角對齊，右上角對齊，左居中對齊，右居中對齊，左下角對齊，右下角對齊，居中。