先看例子

每个弹幕的速度都是不一样的，支持弹幕整体开始暂停。
如果弹幕实在是太多了，有个缓冲队列，不停的重试能否显示，保证文字都能显示全，并且每条都能显示。

实现是基于 CADisplayLink 实现的，如此来说比直接搞个定时器来计算偏移丝滑，简单的平移动画如下：

import UIKit

class ViewController: UIViewController {
    
    let squareView = UIView()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建 CADisplayLink 对象
        let displayLink = CADisplayLink(target: self, selector: #selector(update))
        
        // 将视图控制器添加到 displayLink 中
        displayLink.add(self, for: .common)
        
        // 设置视图属性
        squareView.frame = CGRect(x: 50, y: 50, width: 100, height: 100)
        squareView.backgroundColor = UIColor.red.withAlphaComponent(0.5)
        view.addSubview(squareView)
    }
    
    @objc func update(_ displayLink: CADisplayLink) {
        // 在每一帧更新时移动视图
        squareView.frame.origin.x += 5
    }
}

在这个基础版本上稍微改了改就变成如下代码：

import Foundation
import UIKit

class XDanMu {
    var row: Int = 0
    var label: UILabel = UILabel()
    var speed: CGFloat = 0
    var isMe: Bool = false
}

class XDanMuView: UIView {
    var displayLink: CADisplayLink?
    
    var lineHeight: CGFloat = 26
    var gap: CGFloat = 20
    var minSpeed: CGFloat = 1
    var maxSpeed: CGFloat = 2
    var isPause: Bool = false
    
    var danmus: [XDanMu] = []
    var danmuQueue: [(String, Bool)] = []
    var timer: Timer?
    
    func start() {
        displayLink = CADisplayLink(target: self, selector: #selector(update))
        displayLink?.add(to: RunLoop.current, forMode: .common)
        
        timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(handleDanMuQueue), userInfo: nil, repeats: true)
    }
    
    @objc func handleDanMuQueue() {
        if danmuQueue.isEmpty {
            return
        }
        let danmu = danmuQueue.removeFirst()
        addDanMu(text: danmu.0, isMe: danmu.1)
    }
    
    @objc func addDanMu(text: String, isMe: Bool) {
        let danmu = XDanMu()
        danmu.label.frame.origin.x = self.frame.size.width
        danmu.label.text = text
        danmu.label.sizeToFit()
        
        if isMe {
            danmu.label.layer.borderWidth = 1
        }
        
        var linelasts: [XDanMu?] = []
        let rows: Int = Int(self.frame.size.height / lineHeight)
        for _ in 0..<rows {
            linelasts.append(nil)
        }
        
        for d in danmus {
            if d.row >= linelasts.count {
                break
            }
            if linelasts[d.row] != nil {
                let endx = danmu.label.frame.origin.x
                let targetx = linelasts[d.row]!.label.frame.origin.x
                if endx > targetx {
                    linelasts[d.row] = d
                }
            } else {
                linelasts[d.row] = d
            }
        }
        
        var isMatch = false
        for index in 0..<linelasts.count {
            if let d = linelasts[index] {
                let endx = d.label.frame.origin.x + d.label.frame.size.width + gap
                if endx < self.frame.size.width {
                    danmu.row = index
                    var ms = self.frame.size.width / endx * d.speed
                    ms = CGFloat.minimum(ms, maxSpeed)
                    danmu.speed = CGFloat.random(in: minSpeed...ms)
                    isMatch = true
                    break
                }
            } else {
                danmu.row = index
                danmu.speed = CGFloat.random(in: minSpeed...maxSpeed)
                isMatch = true
                break
            }
        }
        
        if isMatch == false {
            danmuQueue.append((text, isMe))
            return
        }
        
        danmu.label.frame.origin.y = lineHeight * CGFloat(danmu.row)
        
        self.addSubview(danmu.label)
        self.danmus.append(danmu)
    }
    
    @objc func update(_ displayLink: CADisplayLink) {
        if isPause == true {
            return
        }
        // 在每一帧更新时移动视图
        for index in 0..<danmus.count {
            let danmu = danmus[index]
            danmu.label.frame.origin.x -= danmu.speed
            if danmu.label.frame.origin.x < -danmu.label.frame.size.width {
                danmu.label.removeFromSuperview()
                danmus.remove(at: index)
                break
            }
        }
    }
}

再找个需要使用的地方加入如下使用的代码，即可实现上图的效果

override func viewDidLoad() {
    super.viewDidLoad()
    var danmuView: XDanMuView = XDanMuView()
    danmuView.frame = .init(x: 0, y: 100, width: self.view.frame.size.width, height: self.view.frame.size.height - 200)
    self.view.addSubview(danmuView)

    // 配置项
    danmuView.minSpeed = 1
    danmuView.maxSpeed = 2
    danmuView.gap = 20
    danmuView.lineHeight = 30

    // 启动弹幕
    danmuView.start()
    // 启动一个定时器灌弹幕
    timer = Timer.scheduledTimer(timeInterval: 0.4, target: self, selector: #selector(addDanMu), userInfo: nil, repeats: false)
}

@objc func addDanMu() {
    let interval = CGFloat.random(in: 0.3...1.0)
    Timer.scheduledTimer(timeInterval: interval, target: self, selector: #selector(addDanMu), userInfo: nil, repeats: false)
    
    var text = ""
    for _ in 0...Int.random(in: 1...30) {
        text += "嘿"
    }
    for _ in 0...Int.random(in: 1...2) {
        danmuView.addDanMu(text: text, isMe: Bool.random())
    }
}

文本的字体自行根据需求修改，目前是没有增加样式跟颜色。
完整工程传送门
github
gitee