Swift iOS-如何从AVPlayerItemStatus访问错误？

Question

我正在使用AVPlayer播放视频URL。我按照苹果的代码播放视频并处理错误：

在“ 响应状态更改 ”部分中，有一个带有.failed案例的switch语句，注释掉的代码说：// Player item failed. See error.我在此放置了一个断点，使它运行了几次。

问题是我看不到任何NSError类型的变量，它可以让我选择实际打印出错误的类型。我如何找出.failed错误是什么？

观察玩家的状态：

let url: URL = // Asset URL
var asset: AVAsset!
var player: AVPlayer!
var playerItem: AVPlayerItem!

// Key-value observing context
private var playerItemContext = 0

let requiredAssetKeys = [
    "playable",
    "hasProtectedContent"
]

func prepareToPlay() {
    // Create the asset to play
    asset = AVAsset(url: url)

    // Create a new AVPlayerItem with the asset and an
    // array of asset keys to be automatically loaded
    playerItem = AVPlayerItem(asset: asset,
                              automaticallyLoadedAssetKeys: requiredAssetKeys)

    // Register as an observer of the player item's status property
    playerItem.addObserver(self,
                           forKeyPath: #keyPath(AVPlayerItem.status),
                           options: [.old, .new],
                           context: &playerItemContext)

    // Associate the player item with the player
    player = AVPlayer(playerItem: playerItem)
}

响应状态变化

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

    // Only handle observations for the playerItemContext
    guard context == &playerItemContext else {
        super.observeValue(forKeyPath: keyPath,
                           of: object,
                           change: change,
                           context: context)
        return
    }

    if keyPath == #keyPath(AVPlayerItem.status) {
        let status: AVPlayerItemStatus
        if let statusNumber = change?[.newKey] as? NSNumber {
            status = AVPlayerItemStatus(rawValue: statusNumber.intValue)!
        } else {
            status = .unknown
        }

        // Switch over status value
        switch status {
        case .readyToPlay:
            // Player item is ready to play.
        case .failed:
            // Player item failed. See error.
        case .unknown:
            // Player item is not yet ready.
        }
    }
}

Answer 1

如果状态为，.failed则可以AVPlayer像这样从自身访问错误。

    switch status {
    case .readyToPlay:
        // Player item is ready to play.
    case .failed:
        handleErrorWithMessage(player.currentItem?.error?.localizedDescription, error:player.currentItem?.error)
    case .unknown:
        // Player item is not yet ready.
    }

查找以下功能。

func handleErrorWithMessage(_ message: String?, error: Error? = nil) {
    print("Error occured with message: \(message), error: \(error).")
}

希望这可以帮助。