ios - 如何从音乐库mediaPicker和文件应用documentPicker获取音频元数据？

Question

在 Swift 4 中，我不知道如何在导入音频文件时从文档选取器获取音频元数据，以及在从用户媒体库中选取媒体项目时如何从媒体选取器获取音频元数据。我目前正在将 url 从两种导入方法转换为 AVAudioPlayer 项目。谁能告诉我一个方法，即使我必须为 mediaPicker 和 documentPicker 分别编写代码？

func mediaPicker(_ mediaPicker: MPMediaPickerController, didPickMediaItems mediaItemCollection: MPMediaItemCollection) {

    for song in mediaItemCollection.items as [MPMediaItem] {

        // AVAudioPlayer
        let url = song.value(forProperty: MPMediaItemPropertyAssetURL) as? NSURL

        audioPlayer = try? AVAudioPlayer(contentsOf: url! as URL)
        audioPlayer.prepareToPlay()
        audioPlayer.play()
    }

    mediaPicker.dismiss(animated: true, completion: nil)
}


    func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentAt url: URL) {
    guard controller.documentPickerMode == .import else { return }

    let fileURL = url

    let url = url.deletingPathExtension()

    audioPlayer = try? AVAudioPlayer(contentsOf: fileURL)
    audioPlayer.enableRate = true
    audioPlayer.prepareToPlay()
    audioPlayer.play()
    updateCurrentTrack()
}

Answer 1

这不只是遵循文档的问题吗？

1. 使用 URL 形成一个 AVAsset。

   https://developer.apple.com/documentation/avfoundation/avurlasset/1385698-init

2. 现在提取元数据。

   https://developer.apple.com/documentation/avfoundation/avasset/1390498-commonmetadata

3. 现在获取所需的元数据项:

   https://developer.apple.com/documentation/avfoundation/avmetadataitem/1385843-metadataitems

4. 您现在拥有一个或多个 AVMetadataItem 对象。要检索值，请使用异步键值加载:

   https://developer.apple.com/documentation/avfoundation/avasynchronouskeyvalueloading