【Swift 2.0】实现简单弹幕功能

前言

　　简单实现弹幕功能，表跟我谈效率，但也有用队列控制同时弹的数量。

声明
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正文

    let DANMAKU_SPEED: CGFloat =     // 弹幕每秒移动速度
    let DANMAKU_SPACE_TIME: NSTimeInterval =     // 弹幕之间的时间间隔
    let DANMAKU_MAX_ROW =     // 最多同时弹幕行数
    let danmakuFont = UIFont.systemFontOfSize()    // 弹幕字体大小
    var rowArray = Array<Array<Danmaku>>(count: , repeatedValue: Array<Danmaku>())
    var danmakuQueue = NSOperationQueue()    // 队列

    class Danmaku : NSObject{
        var msg: Msg
        var view: UILabel?
        var size = CGSize(width: , height: )
        var row =
        var startTime: NSDate?
        var duration: NSTimeInterval =
        var delay: NSTimeInterval = 

        init(_ msg: Msg, _ row: Int, _ delay: NSTimeInterval = ) {
            self.msg = msg
            self.row = row
            self.delay = delay
        }
    }

    func queueDanmaku(msg: Msg) {
        danmakuQueue.addOperation(NSBlockOperation(block: { [weak self] in

            if let weakself = self {
                repeat {
                    //检测放第几行
                    for var row = ; row < weakself.DANMAKU_MAX_ROW; ++row {
                        let rowDanmaku = weakself.rowArray[row]
                        if rowDanmaku.count ==  {
                            let danmaku = Danmaku(msg, weakself.danmakuFont, row)
                            weakself.rowArray[row].append(danmaku)
                            self?.performSelectorOnMainThread("sendDanmaku:", withObject: danmaku, waitUntilDone: true)
                            return
                        } else {
                            if let lastDanmaku = rowDanmaku.last {
                                if let startTime = lastDanmaku.startTime {
                                    let now = NSDate()
                                    let seconds = now.timeIntervalSinceDate(startTime)
                                    let widthDuration = Double(lastDanmaku.size.width / weakself.DANMAKU_SPEED)

                                    var delay = seconds - weakself.DANMAKU_SPACE_TIME - widthDuration
                                    if delay >=  {
                                        delay =
                                    } else {
                                        if lastDanmaku.delay > lastDanmaku.duration {
                                            continue
                                        }
                                    }

                                    let danmaku = Danmaku(msg, weakself.danmakuFont, row, abs(delay) + lastDanmaku.delay)
                                    weakself.rowArray[row].append(danmaku)

                                    self?.performSelectorOnMainThread("sendDanmaku:", withObject: danmaku, waitUntilDone: true)
                                    return
                                }
                            }
                        }
                    }

                    sleep()
                } while self != nil
            }

            }))
    }

    func sendDanmaku(danmaku: Danmaku) {
        let text = "\(danmaku.msg.user_name) : \(danmaku.msg.text)"
        let size = NSString(string: text).sizeWithAttributes([NSFontAttributeName : danmakuFont])
        let width = UIScreen.mainScreen().bounds.size.width
        let top =  + danmaku.row * (Int(size.height) + )
        let label = UILabel(frame: CGRectMake(width, CGFloat(top), size.width, size.height))
        let duration = (width + size.width) / DANMAKU_SPEED

        danmaku.view = label
        danmaku.size = size
        danmaku.startTime = NSDate()
        danmaku.duration = NSTimeInterval(duration)

        label.text = text
        label.font = danmakuFont
        label.textColor = UIColor.whiteColor()
        label.shadowColor = UIColor.blackColor()
        label.shadowOffset = CGSizeMake(, -1.0)

        self.view.addSubview(label)
        UIView.animateWithDuration(Double(duration), delay: danmaku.delay, options: UIViewAnimationOptions.CurveLinear, animations: { () -> Void in
                label.left = -label.width
            }) { [weak self] (Bool) -> Void in
                if !(self?.rowArray[danmaku.row].isEmpty ?? true) {
                    self?.rowArray[danmaku.row].removeFirst()
                }
                label.removeFromSuperview()
        }
    }

　　　　代码说明：

　　　　　　代码控制了最多同时只能弹三行，每行最后一条如果延迟大于跑弹幕的时间（已经有一条处于完全等待状态）就自动切到下一行，超过最大限制就等待。

　　　　　　*　　rowArray 主要用于查询前一个弹幕的位置和时间

　　　　　　*　　别忘了在 deinit 里面加上 danmakuQueue.cancelAllOperations()

　　　　　　*　　注意 NSBlockOperation 的 block 并不在主线程上