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UILabel用来在界面上显示一行或多行文本，下面就介绍常见属性与基本用法。

1、UILabel创建####

//创建的时候设置frame
let testLable=UILabel(frame:CGRect(x:20,y:100,width:self.view.frame.size.width - 40,height:400))
        
//先创建，在进行位置大小设定，和上面的作用一样的      
let Label = UILabel()
Label.frame = CGRect(x:20,y:100,width:self.view.frame.size.width - 40,height:400)

//添加       
self.view.addSubview(Label);

2、UILabel常见属性设置####

//显示文本内容
testLable.text = "nice to meet you!"

//背景颜色
testLable.backgroundColor = UIColor.green

//文字颜色
testLable.textColor = UIColor.white

//文字对齐方式
testLable.textAlignment = NSTextAlignment.left

其中文字对齐方式有以几种：
 /* Values for NSTextAlignment */
 @available(iOS 6.0, *)
 public enum NSTextAlignment : Int {
 
 
 case left // Visually left aligned
 
 
 case center // Visually centered
 
 case right // Visually right aligned
 
 /* !TARGET_OS_IPHONE */
 // Visually right aligned
 // Visually centered
 
 case justified // Fully-justified. The last line in a paragraph is natural-aligned.
 
 case natural // Indicates the default alignment for script
 }


//阴影颜色
testLable.shadowColor = UIColor.black

//阴影偏移位置
testLable.shadowOffset = CGSize(width:-5,height:5)

//根据视图宽度自动调整文字大小
testLable.adjustsFontSizeToFitWidth = true

//高亮时候的文字颜色
testLable.highlightedTextColor = UIColor.cyan
        
//设置圆角
testLable.layer.cornerRadius = 20
testLable.layer.masksToBounds = true

//边框的宽度和颜色
testLable.layer.borderColor = UIColor.green.cgColor
testLable.layer.borderWidth = 2
     
//文字类型/大小   
testLable.font = UIFont.boldSystemFont(ofSize: 20) //加粗类型
testLable.font = UIFont.systemFont(ofSize: 20)//文字大小
testLable.font = UIFont.italicSystemFont(ofSize: 20)//斜体类型

//大小和文字一起设置
testLable.font = UIFont(name:"您好",size:50)

//显示样式
testLable.lineBreakMode = NSLineBreakMode.byCharWrapping

// NSParagraphStyle
@available(iOS 6.0, *)
public enum NSLineBreakMode : Int {

case byWordWrapping // Wrap at word boundaries, default

case byCharWrapping // Wrap at character boundaries

case byClipping // Simply clip

case byTruncatingHead // Truncate at head of line: "...wxyz"

case byTruncatingTail // Truncate at tail of line: "abcd..."

case byTruncatingMiddle // Truncate middle of line:  "ab...yz"
}

//多行显示
label.numberOfLines = 2//最多显示2行
label.numberOfLines = 0// 默认没有行数显示
label.numberOfLines = 1//只能显示一行

3、富文本设置####

//创建对象
let attributeString = NSMutableAttributedString(string:"Welcome to Swift! Welcome to Swift! Welcome to Swift! Welcome to Swift!")
//设置字体大小/字体类型
attributeString.addAttribute(NSFontAttributeName, value: UIFont(name: "HelveticaNeue-Bold", size: 16)!, range: NSMakeRange(0, 6))
//设置背景颜色           
attributeString.addAttribute(NSForegroundColorAttributeName, value: UIColor.red, range: NSMakeRange(0, 3))          
//设置文档背景色     attributeString.addAttribute(NSBackgroundColorDocumentAttribute, value: UIColor.lightGray, range: NSMakeRange(10, 10))
//设置下划线
attributeString.addAttribute(NSUnderlineStyleAttributeName, value:NSUnderlineStyle.StyleSingle.rawValue, range: NSMakeRange(5,12))
        
testLable.attributedText = attributeString;

4、文本高度计算####

关于lable显示文本的高度计算也是老生常谈，下面就简单的举个例子以extension为例：

extension NSString {
    func textSizeWithFont(font: UIFont, constrainedToSize size:CGSize) -> CGSize {
        var textSize:CGSize!
        if CGSizeEqualToSize(size, CGSizeZero) {
            let attributes = NSDictionary(object: font, forKey: NSFontAttributeName)
            textSize = self.sizeWithAttributes(attributes)
        } else {
            let option = NSStringDrawingOptions.UsesLineFragmentOrigin
            let attributes = NSDictionary(object: font, forKey: NSFontAttributeName)
            let stringRect = self.boundingRectWithSize(size, options: option, attributes: attributes, context: nil)
            textSize = stringRect.size
        }
        return textSize
    }
}