使用AVPlayer.currentItem?资产.duration使UI停止一段时间

Question

我有一个函数，播放歌曲与我在它的参数中给出的url。我用AVPlayer来做这个。

func playSong(url:URL) {
self.playerItem = AVPlayerItem(url: url)
self.avPlayer = AVPlayer(playerItem: playerItem)
self.avPlayer.automaticallyWaitsToMinimizeStalling = false
self.avPlayer!.volume = 1.0
self.avPlayer.play()
let duration = (self.avPlayer.currentItem?.asset.duration)!
let totalDuration : CMTime = duration
let seconds : Float64 = CMTimeGetSeconds(totalDuration)
self.totalAudioPlaybackTime.text = self.stringFromTimeInterval(interval: seconds)
self.sliderProgress.maximumValue = Float(seconds)
self.timeObserver = self.avPlayer.addPeriodicTimeObserver(forInterval: CMTime.init(value: 1, timescale: 1), queue: .main, using: { time in
if let duration = self.avPlayer.currentItem?.duration{
let time : Float64 = CMTimeGetSeconds(self.avPlayer!.currentTime())
self.sliderProgress.value = Float(time)
self.currentTime.text = self.stringFromTimeInterval(interval: time)
}
})
}

其他一切都很好，但唯一的问题是在

行

let duration = (self.avPlayer.currentItem?.asset.duration)!

当执行这一行时，它需要5到6秒(有时甚至是10秒)来计算持续时间，当这发生时，UI只是冻结，直到计算出持续时间。我不知道为什么会这样。请让我知道我做错了什么

Answer 1

你应该从后台线程加载duration。

可以使用新的swift并发

Task {
let duration = try await asset.load(.duration)
}

苹果文档:https://developer.apple.com/documentation/avfoundation/media_assets/loading_media_data_asynchronously