如何使用AVPlayer addBoundaryTimeObserver？

Question

我正在通过点击 UI 中的按钮手动记录歌曲的节拍数。

之后，每次 arrayOfBeats 的键与 playerItem.currentTime

匹配时，我想再次播放歌曲 addBoundaryTimeObserver

如何将 arrayOfBeats 的键输入到 addBoundaryTimeObserver 方法？

   //save the time as a string with 2 decimal places
  let timeString = String(format: "%.2f", strongSelf.timeInSeconds)

 let arrayOfBeats = ["2.18": 3, "3.38": 5, "3.63": 6] // x.y seconds : beatCount
 var timeObserverToken:Any!

   func addBoundaryTimeObserver(url: URL) {

    let playerItem = AVPlayerItem(url: url)
    player = AVPlayer(playerItem: playerItem)

  // Build boundary times from arrayOfBeats keys
    let keys = arrayOfBeats.keys.compactMap {[=10=]}

    // how can I convert keys to to NSValue as in  https://developer.apple.com/documentation/avfoundation/avplayer/1388027-addboundarytimeobserver

   var times = [NSValue]()
   let mainQueue = DispatchQueue.main
   player?.play()

   timeObserverToken =
        player?.addBoundaryTimeObserver(forTimes: times, queue: mainQueue) {
        //update label with beatCount every time duration of audio file is transversed and it matches an element in  var times = [NSValue]()
  }
}//end addBoundaryTimeObserver

Answer 1

根据文档

times - An array of NSValue objects containing CMTime values representing the times at which to invoke block.

您需要创建适当的 CMTime 结构，然后创建 NSValue 个对象的数组：

let cmtime = CMTime(seconds: 2.18, preferredTimescale: 100)
let cmtimevalue = NSValue(time: cmtime)
let cmtimevalueArray = [cmtimevalue]

请注意，此初始化程序的秒数是 Double 并且 timescale 是 CMTimeScale 又名 Int32

此外，您的 arrayOfBeats 不是 Array，而是 Dictionary，并且字典中的项目未排序。您可能得不到想要的订单。

使用元组数组可能会更好。

let arrayOfBeats = [("2.18", 3), ("3.38", 5), ("3.63", 6)]

将您的 String 秒值转换回 Double 是您的（微不足道的）问题。

如何使用AVPlayer addBoundaryTimeObserver？

How to use AVPlayer addBoundaryTimeObserver?

swift

avplayer