UI绘图与信息、样式

UI的绘图功能是在视图尺寸确定以后，将信息和样式绘制的过程；

给信息和样式的修改提供的最后的机会。

UILabel 控制行段间距的终极代码。

class LineSpaceLabel: UILabel {

var lineSpace = 2.0

var paragraphSpace = 0.0

override func draw(_ rect: CGRect) {

/*

paragraphStyle.lineSpacing = 10;// 字体的行间距

paragraphStyle.firstLineHeadIndent = 20.0f;//首行缩进

*/

var attributeString = NSMutableAttributedString(string:self.text ?? "")

if let attrStr = self.attributedText

{

attributeString = NSMutableAttributedString.init(attributedString: attrStr)

}

let paraStyle = NSMutableParagraphStyle()

paraStyle.lineSpacing = CGFloat(lineSpace) //行间距

paraStyle.paragraphSpacing = CGFloat(paragraphSpace)

attributeString.addAttribute(NSAttributedStringKey.paragraphStyle,

value: paraStyle,

range: attributeString.rangeOfSelf())

self.attributedText = attributeString

super.draw(rect)

}

}