func showAllFonts(){

        let familyNames = UIFont.familyNames

        var index:Int = 0

        for familyName in familyNames {

            let fontNames = UIFont.fontNames(forFamilyName: familyName as String)

            for fontName in fontNames

            {

                index += 1

                print("第 \(index) 个字体，字体font名称：\(fontName)")

            }

        }

    }