首先新建一個類MyLabel繼承自UILabel,程式碼如下

#import <UIKit/UIKit.h>

typedef enum
{
    VerticalAlignmentTop=0,
    VerticalAlignmentMiddle,//default
    VerticalAlignmentBottom,
    
}VerticalAlignment;

@interface MyLabel : UILabel
{
    @private
    VerticalAlignment _verticalAlignment;
}

@property(nonatomic)VerticalAlignment verticalAlignment;

@end
 

#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 setNeedsDisplay];//重繪一下
}

-(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 VerticalAlignmentMiddle:
            textRect.origin.y=bounds.origin.y+(bounds.size.height-textRect.size.height)/2.0;
            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];//重新計算位置
    [super drawTextInRect:actualRect];
}

@end
 

MyLabel *lbl = [[MyLabel alloc] initWithFrame:CGRectMake(20, 20, 150, 300)];
   
    lbl.textAlignment = UITextAlignmentCenter;
    lbl.textColor = [UIColor redColor];
    lbl.lineBreakMode = UILineBreakModeWordWrap;
    lbl.numberOfLines = 0;
    [email protected]"My Content";
    [lbl setVerticalAlignment:VerticalAlignmentMiddle];
    [self.view addSubview:lbl];