ios - 当AVPlayer项为 ".readyToPlay"时如何仅播放videoPreviewLayer

Question

我正在努力实现与 snapchat 相同的目标。也就是说，当用户完成拍摄视频并进入预览 View 时，视频会卡住一秒钟左右，直到视频准备好播放为止，然后开始播放。我正在努力实现同样的目标。以下是我尝试过的，

            while playerItem1.status == .unknown {
            print("1111121232432431243123241432143243214324321")
            if playerItem1.status == .readyToPlay {

                playerQueue = AVQueuePlayer(playerItem: playerItem1)
                self.playerQueue?.play()

                playerLayer = AVPlayerLayer(player: playerQueue)
                playerLayer.frame = (camPreview?.bounds)!
                playerLayer?.layoutIfNeeded()
                playerLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill

                camPreview?.layer.insertSublayer(playerLayer, above: previewLayer)

                playerLooper = AVPlayerLooper(player: playerQueue, templateItem: playerItem1)
            }
        }

然而这会导致 xcode 崩溃，因为它似乎永远不会结束。我不明白这一点，因为在某些时候状态应该变成 .readyToPlay，因为如果我不理会它，它就会这样做。

主要是我想这样做，因为目前当您放开我的代码中的捕获按钮时，屏幕会卡住然后进行转换。我希望它卡住视频而不是捕获屏幕。

    extension ViewController: AVCaptureFileOutputRecordingDelegate {
    //MARK: - Protocal stubs
    func capture(_ captureOutput: AVCaptureFileOutput!, didStartRecordingToOutputFileAt fileURL: URL!, fromConnections connections: [Any]!) { print("bruh? MMMM") }

    func capture(_ captureOutput: AVCaptureFileOutput!, didFinishRecordingToOutputFileAt outputFileURL: URL!, fromConnections connections: [Any]!, error: Error!) {
    }

    func fileOutput(_ output: AVCaptureFileOutput, didFinishRecordingTo outputFileURL: URL, from connections: [AVCaptureConnection], error: Error?) {

        if (error != nil) {
            print("Error recording movie11: \(error!.localizedDescription)")
        } else {
            newViewVideoPlayback()

            switchIcon.isHidden = true
            switchWhiteUI.isHidden = true
            switchCamButton.isHidden = true
            camWhiteLine.isHidden = true

//            let videoRecorded = outputURL! as URL
//            playerItem1 = AVPlayerItem(url: videoRecorded)


            if !captureSession.isRunning {
                DispatchQueue.global(qos: .background).async {
                    self.startRunningCaptureSession()
                }
            }
        }

    }
    let videoRecorded = outputURL! as URL
    playerItem1 = AVPlayerItem(url: videoRecorded)

    playerItem1.addObserver(self,
    forKeyPath: #keyPath(AVPlayerItem.status),
    options: [.old, .new],
    context: &playerItemContext)

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

            // Switch over status value
            switch status {
            case .readyToPlay:
            // Player item is ready to play.

                playerQueue = AVQueuePlayer(playerItem: playerItem1)
                self.playerQueue?.play()

                playerLayer = AVPlayerLayer(player: playerQueue)
                playerLayer.frame = (camPreview?.bounds)!
                playerLayer?.layoutIfNeeded()
                playerLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill

                camPreview?.layer.insertSublayer(playerLayer, above: previewLayer)

                playerLooper = AVPlayerLooper(player: playerQueue, templateItem: playerItem1)

            case .failed: break
            // Player item failed. See error.
            case .unknown: break
                // Player item is not yet ready.
            }
        }
    }

}

Answer 1

来自Docs

When a player item is created, its status is AVPlayerItem.Status.unknown, meaning its media hasn’t been loaded and has not yet been enqueued for playback. Associating a player item with an AVPlayer immediately begins enqueuing the item’s media and preparing it for playback. When the player item’s media has been loaded and is ready for use, its status will change to AVPlayerItem.Status.readyToPlay. You can observe this change using key-value observing.

因此，您需要监听状态，而不是制作一个 while 循环，该循环会压垮系统，直到状态发生变化，这也在 Docs 中。

private var playerItemContext = 0
playerItem.addObserver(self,
                           forKeyPath: #keyPath(AVPlayerItem.status),
                           options: [.old, .new],
                           context: &playerItemContext)

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.
        }
    }
}

<小时/>

extension ViewController: AVCaptureFileOutputRecordingDelegate {
    //MARK: - Protocal stubs
    func capture(_ captureOutput: AVCaptureFileOutput!, didStartRecordingToOutputFileAt fileURL: URL!, fromConnections connections: [Any]!) { print("bruh? MMMM") }

    func capture(_ captureOutput: AVCaptureFileOutput!, didFinishRecordingToOutputFileAt outputFileURL: URL!, fromConnections connections: [Any]!, error: Error!) {
    }

    func fileOutput(_ output: AVCaptureFileOutput, didFinishRecordingTo outputFileURL: URL, from connections: [AVCaptureConnection], error: Error?) {

        if (error != nil) {
            print("Error recording movie11: \(error!.localizedDescription)")
        } else {
            newViewVideoPlayback()

            switchIcon.isHidden = true
            switchWhiteUI.isHidden = true
            switchCamButton.isHidden = true
            camWhiteLine.isHidden = true

             let videoRecorded = outputURL! as URL
             playerItem1 = AVPlayerItem(url: videoRecorded)
              playerItem1.addObserver(self,
              forKeyPath: #keyPath(AVPlayerItem.status),
              options: [.old, .new],
              context: &playerItemContext) 
              playerQueue = AVQueuePlayer(playerItem: playerItem1)

            if !captureSession.isRunning {
                DispatchQueue.global(qos: .background).async {
                    self.startRunningCaptureSession()
                }
            }
        } 
    } 
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: AVPlayerItem.Status
            if let statusNumber = change?[.newKey] as? NSNumber {
                status = AVPlayerItem.Status(rawValue: statusNumber.intValue)!
            } else {
                status = .unknown
            }

            // Switch over status value
            switch status {
            case .readyToPlay: 
                playerLayer = AVPlayerLayer(player: playerQueue)
                playerLayer.frame = (camPreview?.bounds)!
                playerLayer?.layoutIfNeeded()
                playerLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill 
                camPreview?.layer.insertSublayer(playerLayer, above: previewLayer) 
                playerLooper = AVPlayerLooper(player: playerQueue, templateItem: playerItem1) 
                // Player item is ready to play. 
                self.playerQueue?.play(
            case .failed: break
            // Player item failed. See error.
            case .unknown: break
                // Player item is not yet ready.
            }
        }
   } 
}