从iOS 6及以后，UITextAlignment已弃用。使用NSTextAlignment

myLabel.textAlignment = NSTextAlignmentCenter;

Swift版本来自iOS 6及更高版本

myLabel.textAlignment = .center

在Swift 4.2和Xcode 10中

let lbl = UILabel(frame: CGRect(x: 10, y: 50, width: 230, height: 21))
lbl.textAlignment = .center //For center alignment
lbl.text = "This is my label fdsjhfg sjdg dfgdfgdfjgdjfhg jdfjgdfgdf end..."
lbl.textColor = .white
lbl.backgroundColor = .lightGray//If required
lbl.font = UIFont.systemFont(ofSize: 17)

 //To display multiple lines in label
lbl.numberOfLines = 0
lbl.lineBreakMode = .byWordWrapping

lbl.sizeToFit()//If required
yourView.addSubview(lbl)

Label.textAlignment = NSTextAlignmentCenter;

使用yourLabel。textAlignment = NSTextAlignmentCenter;为iOS >= 6.0和yourLabel。textAlignment = UITextAlignmentCenter;适用于iOS < 6.0。

要在Swift的UILabel中居中文本(这是针对iOS 7+)，你可以做:

myUILabel.textAlignment = .Center

Or

myUILabel.textAlignment = NSTextAlignment.Center

注意:根据UILabel类引用，从iOS 6开始，这种方法现在已弃用。

只需使用textAlignment属性来查看使用UITextAlignment值之一所需的对齐。(UITextAlignmentLeft, UITextAlignmentCenter或UITextAlignmentRight。)

例如:[myUILabel setTextAlignment:UITextAlignmentCenter];

更多信息请参见UILabel类参考。