ios - 在 SwiftUI 中监听 AVPlayer timeControlStatus 的变化

Question

因此尝试在 SwiftUI 中实现 AVPlayer 的简单观察者。我已经添加了被触发的观察者，但还没有根据 Apple 文档弄清楚如何/在哪里实现 observeValue:https://developer.apple.com/documentation/avfoundation/media_assets_playback_and_editing/responding_to_playback_state_changes

到目前为止，我的 AVPlayer 类如下:

class Player: AVPlayer, ObservableObject {

    @Published var isPlaying: Bool = false

    static var shared = AVPlayer()
    static var episodeId: Int?

    static func playItem(at itemURL: String, episodeId: Int) {
        let url = URL(string: itemURL)
        Player.shared = AVPlayer(url: url!)
        Player.episodeId = episodeId
        Player.shared.addObserver(self.shared, forKeyPath: "timeControlStatus", options: [.old, .new], context: nil)
    }
}

所以问题是我应该在哪里实现它才能工作:

override func observeValue(forKeyPath keyPath: String?,
                           of object: Any?,
                           change: [NSKeyValueChangeKey : Any]?,
                           context: UnsafeMutableRawPointer?) {
    if Player.shared.timeControlStatus == .playing {
        // Set @Published isPlaying to true
    }
}

Answer 1

它可以像下面这样(不要使用 static 它在这种情况下不需要，无论如何你将需要实例在 @ObservedObject 中使用)

当然不是最终的Player，但是进化的方向应该很明确:

class Player: AVPlayer, ObservableObject {

    @Published var isPlaying: Bool = false

    private var playerContext = 0

    var player: AVPlayer? = nil
    var episodeId: Int?

    func playItem(at itemURL: String, episodeId: Int) {
        guard let url = URL(string: itemURL) else { return }

        // cleanup for previous player
        self.player?.removeObserver(self, forKeyPath: "timeControlStatus")

        // setup new player
        let newPlayer = AVPlayer(url: url)
        newPlayer.addObserver(self, forKeyPath: "timeControlStatus", options: [.old, .new], context: &playerContext)

        self.player = newPlayer
        self.episodeId = episodeId
    }

    override func observeValue(forKeyPath keyPath: String?,
                               of object: Any?,
                               change: [NSKeyValueChangeKey : Any]?,
                               context: UnsafeMutableRawPointer?) {

        guard context == &playerContext else { // give super to handle own cases
               super.observeValue(forKeyPath: keyPath,
                       of: object,
                       change: change,
                       context: context)
               return
        }
        if self.player?.timeControlStatus == .playing {
            self.isPlaying = true
        }
    }
}