ios - 音频无法播放 Xcode 10.1 Swift 4

Question

我终于开始学习播放声音，但我没有成功在我的应用程序中播放声音。我仍然使用 Xcode 10.1/Swift4(不是 4.2)，因为我还无法升级到 Mojave/Catalina。我读了很多关于.setCategory(.playback, mode: .default)的帖子Xcode 10.1 中存在错误，但找到的解决方案适用于 Swift 4.2。另外category:和mode:预计类型为 String ，但在文档中该功能解释为:

func setCategory(_ category: AVAudioSession.Category, mode: AVAudioSession.Mode, options: AVAudioSession.CategoryOptions = []) throws

而且它们不是 String 类型。我在这里有点迷失了。

我的代码不会引发任何编译错误，但在控制台上运行时我得到:

AVAudioSessionUtilities.mm:106:getUInt32: -- Category Value Converter failed to find a match for string "ambient"

我在这里缺少什么？您能给我指出正确的方向来理解这个类别问题吗？一如既往，非常感谢您的时间和帮助。

这是应该播放声音的函数:

static func playOnceSound(soundToPlay: String) {
       var player: AVAudioPlayer?
        guard let url = Bundle.main.url(forResource: soundToPlay, withExtension: "mp3") else { return }



        do {
//            try AVAudioSession.sharedInstance().setCategory(.playback, mode: .default) // Error: Type 'String' has no member 'playback'

            try AVAudioSession.sharedInstance().setCategory("ambient", mode: "default", options: .defaultToSpeaker)
            try AVAudioSession.sharedInstance().setActive(true)

            /* The following line is required for the player to work on iOS 11. Change the file type accordingly*/
            player = try AVAudioPlayer(contentsOf: url, fileTypeHint: AVFileType.mp3.rawValue)

            /* iOS 10 and earlier require the following line:
             player = try AVAudioPlayer(contentsOf: url, fileTypeHint: AVFileTypeMPEGLayer3) */

            guard let player = player else { return }
            player.numberOfLoops = 1
            player.volume = 1.0
            player.play()

        } catch let error {
            print(error.localizedDescription)
        }
    }

Answer 1

您是否尝试过以这种方式输入环境和默认值，而不是使用字符串？另外，在 setCategory 之前实例化 Audio Session 对象:

var audioSession: AVAudioSession?

func setup() {
    audioSession = AVAudioSession.sharedInstance()

    do {
        try audioSession.setCategory(AVAudioSession.Category.ambient, mode: .default, options: .defaultToSpeaker)
        try audioSession.setActive(true)
    }
    catch {
        print("Failed to set category", error.localizedDescription)
    }
}