简单：swift 实现文本横向滚动，跑马灯效果

1.首先放三个控件

headView.addSubview(BG)//可以滚动的视图bg
        BG.addSubview(announceBG)//具体消息内容的bg 必须要有这个 不然消息显示会超出范围
        announceBG.addSubview(announceL)//具体消息内容
 
        BG.snp.makeConstraints { make in
            make.left.equalTo(messageImageV.snp.right).offset(8.point)
            make.top.equalTo(bannerView.snp.bottom).offset(16.point)
            make.right.equalToSuperview().offset(-45.point)
            make.height.equalTo(23.point)
        }
 
        announceBG.snp.makeConstraints { make in
            make.left.equalTo(1.point)
            make.right.equalTo(-1.point)
            make.top.bottom.equalTo(0)
        }
 
        announceL.snp.makeConstraints { make in
            make.top.bottom.equalToSuperview()
            make.left.equalTo(announceBG.snp.right)
        }
 
 
    //MARK: ---- 以下三个控件第二种显示消息跑马灯效果
    //显示消息内容的label
    lazy var announceL: UILabel = {
        let view = UILabel()
        view.text = ""
        view.textColor = .hexColor("#FFFFFF")
        view.textAlignment = .left
        view.font = .font(size: 12, alias: .pfMedium)
        return view
    }()

    lazy var BG: UIView = {
        let view = UIView()
        return view
    }()

    lazy var announceBG: UIView = {
        let view = UIView()
        view.clipsToBounds = true
        return view
    }()
 
 
2.具体实现方法
    funcshowScrollAnimation(content: String) {
           // 如果没有内容移除动画，并隐藏
//           if content.removeAllSapce.count <= 0 {
//               announceL.layer.removeAllAnimations()
//               self.isHidden = true
//               return
//           }

           // 根据文字长度计算一个时间
//          self.isHidden = false
        self.announceL.text = content
        var duration = CGFloat(content.count)/4.0

        //字符串宽度
        let charW = sizeWithText(text: content, font: .systemFont(ofSize: 12), size: .zero)
        let announceBgW = UIScreen.width - 95.point

        if charW < announceBgW + 30 {
            duration = 7
        }

        // 动画
        let anim = CABasicAnimation()
        anim.toValue = -announceBgW-charW
        anim.duration = duration
        anim.repeatCount = MAXFLOAT
        anim.isRemovedOnCompletion = false
        announceL.layer.add(anim, forKey: "transform.translation.x")
    }

    // 计算字符串长度
    funcsizeWithText(text: String, font: UIFont, size: CGSize) -> CGFloat {
        let attributes = [NSAttributedString.Key.font: font]
        let option = NSStringDrawingOptions.usesLineFragmentOrigin
        let width = text.boundingRect(with: size, options: option, attributes: attributes, context: nil).size.width
        return width
    }

3.调用

    self.showScrollAnimation(content: setMessage)