如何知道 AVPlayer 何时准备好播放并将信息发送到控制器

Question

我正在 swift 中构建一个广播流媒体应用程序。目前一切正常，但我想稍微改善一下用户体验。

我有一个 RadioPlayer.swift class 来处理我的无线电操作。

 import Foundation
 import AVFoundation

 class RadioPlayer {
 static let sharedInstance = RadioPlayer()
 private var player = AVPlayer(URL: NSURL(string:"http://rfcmedia.streamguys1.com/classicrock.mp3")!)

private var isPlaying = false


func play() {
    player = AVPlayer(URL: NSURL(string: "http://rfcmedia.streamguys1.com/classicrock.mp3")!)
    player.play()
    isPlaying = true

    player.currentItem?.status

}

func pause() {
    player.pause()
    isPlaying = false
    player.replaceCurrentItemWithPlayerItem(nil)
}

func toggle() {
    if isPlaying == true {
        pause()
    } else {
        play()
    }
}

func currentlyPlaying() -> Bool {
    return isPlaying
}

然后我有一个实现 class 的视图控制器。我的 objective 是当播放器正在加载时，发送一条消息说正在准备流式传输，因此用户知道必须等待（也禁用播放按钮）。

所以我的问题是如何实现这一点，在 android 中我使用广播来发送消息，但我没有在 swift 中找到等效项。

Answer 1

您可以为 AVPlayer 属性添加观察者，例如在 Swift 3:

player.addObserver(self, forKeyPath: "reasonForWaitingToPlay", options: .new, context: &observerContext)

或者在Swift2中，使用.New:

player.addObserver(self, forKeyPath: "reasonForWaitingToPlay", options: .New, context: &observerContext)

注意，这是使用私有属性来识别上下文：

private var observerContext = 0

然后就可以添加观察者方法了。在 Swift 3:

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

    // look at `change![.newKey]` to see what the status is, e.g.

    if keyPath == "reasonForWaitingToPlay" {
        NSLog("\(keyPath): \(change![.newKey])")
    }
}

或在Swift 2:

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
    guard context == &observerContext else {
        super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
        return
    }

    // look at `change![NSKeyValueChangeNewKey]` to see what the status is, e.g.

    if keyPath == "reasonForWaitingToPlay" {
        NSLog("\(keyPath): \(change![NSKeyValueChangeNewKey])")
    }

}

如何知道 AVPlayer 何时准备好播放并将信息发送到控制器

How to know when AVPlayer is ready to play and sent info to the controller

streaming

swift