检测 AVPlayer 和 AVQueuePlayer KVO 之间的区别

Question

我有一个AVPlayer 用于在线音频流和AVQueuePlayer 用于离线队列以播放多首歌曲。

我的代码

self.myQueuePlayer?.addObserver(self, forKeyPath: "timedMetadata", options: NSKeyValueObservingOptions.new, context: nil)

myPlayer.currentItem?.addObserver(self, forKeyPath: "timedMetadata", options: [.new,.old,.initial], context: nil)

我如何观察“timedMetadata”的 KVO 并获取它是 AVPlayer 还是 AVQueuePlayer？

Answer 1

您可以使用上下文参数来区分不同的 KVO 对象：

// class
private var playerContext = 0
private var queuePlayerContext = 0

func setup() {
    self.myQueuePlayer?.addObserver(self, forKeyPath: "timedMetadata", options: .new, context: &queuePlayerContext)
    myPlayer.currentItem?.addObserver(self, forKeyPath: "timedMetadata", options: .new, context: &playerContext)
}

override open func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    guard let context = context else {
        return
    }

    if keyPath == "timedMetadata" {
        switch context {
        case &queuePlayerContext:
            print("queuePlayer")
        case &playerContext:
            print("playerContext")
        default:
            break
        }
    }
}