如何从AVAudioPlayer中的核心数据播放NSData [英] How to play NSData from Core Data in AVAudioPlayer

问题描述

我将mp3文件作为NSData二进制数据保存到Core Data中.然后，我在NSFetchedResultsController的帮助下加载此文件.然后，我编写了以下代码，但出现了错误.我该如何解决?

I save mp3 file into Core Data as NSData binary data. Then I load this file with help of NSFetchedResultsController. Then I wrote following code but I got the error. How can I fix it?

致命错误:解开可选值时意外发现nil

fatal error: unexpectedly found nil while unwrapping an Optional value

var audioPlayer = AVAudioPlayer()
func play() {
    if musicData != nil {
        audioPlayer = AVAudioPlayer(data: musicData, error: nil)
        AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback, error: nil)
        AVAudioSession.sharedInstance().setActive(true, error: nil)
        audioPlayer.prepareToPlay()
        audioPlayer.play()
    }
}

更新 我检查了一下，发现AVAudioPlayer为nil，但我在本课开始时就将此玩家初始化.

UPDATE I checked it and I saw that AVAudioPlayer is nil but I init this player in beginning of this class.

仍然更改了代码，但出现了相同的错误 第二种方法

Still I changed code but I get the same error The second method

var av = AVAudioPlayer()
func play() {
    let object = fetchedResultsController.fetchedObjects?.first as! Entity
    let songData = object.mp3

    var urlData: NSURL!
    songData.writeToURL(urlData, atomically: true)
    av = AVAudioPlayer(contentsOfURL: urlData, error: nil)
    av.prepareToPlay()
    av.play()
}

推荐答案

我添加了文件类型提示，并且对我有用.

I added the file type hint and it works for me.

  func playMusic() {
        let url = NSBundle.mainBundle().URLForResource("Music", withExtension: "mp3")!
        let data = NSData(contentsOfURL: url)!
        AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback, error: nil)
        AVAudioSession.sharedInstance().setActive(true, error: nil)
        audioPlayer = AVAudioPlayer(data: data, fileTypeHint: AVFileTypeMPEGLayer3, error: nil)
        audioPlayer.prepareToPlay()
        audioPlayer.play()
    }

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