在 Swift 中按顺序播放音频文件，其中第二个声音重复播放

Question

对于我游戏中的背景音乐，我想播放两个声音。第一个声音在开始时只播放一次（4 小节介绍）。之后，第二个声音（主音乐）无限循环播放。不幸的是，下面的代码同时播放声音，而不是按顺序播放（当我查看 AVQueuePlayer 时，我无法弄清楚如何只循环两个声音中的第二个）：

var backgroundMusicPlayer: AVAudioPlayer!
var backgroundMusicPlayerIntro: AVAudioPlayer!

func playBackgroundMusic(filename: String, withIntro intro: String) {
    let resourceUrl = Bundle.main.url(forResource: filename, withExtension: nil)
    let resourceUrlIntro = Bundle.main.url(forResource: intro, withExtension: nil)

    guard let url = resourceUrl, let urlIntro = resourceUrlIntro else {
        print("Could not find files: \(intro) and/or \(filename)")
        return
    }

    //play the intro first before playing the main loop
    do {
        try backgroundMusicPlayerIntro = AVAudioPlayer(contentsOf: urlIntro)
        backgroundMusicPlayerIntro.numberOfLoops = 1
        backgroundMusicPlayerIntro.prepareToPlay()
        backgroundMusicPlayerIntro.play()
    } catch {
        print("Could not create audio player!")
        return
    }

    //main music that gets played on repeat
    do {
        try backgroundMusicPlayer = AVAudioPlayer(contentsOf: url)
        backgroundMusicPlayer.numberOfLoops = -1
        backgroundMusicPlayer.prepareToPlay()
        backgroundMusicPlayer.play()
    } catch {
        print("Could not create audio player!")
        return
    }
}

Answer 1

您同时启动 2 个玩家。您可以使用一个播放器属性，当在第一个声音结束时调用audioPlayerDidFinishPlaying 方法时，AVAudioPlayerDelegate 可以播放第二个声音。基本上是这样的：

class Player: AVAudioPlayerDelegate {

    var audioPlayer: AVAudioPlayer?

    func startPlayingFirstSong() {
        // your 1st do/catch code...
        try audioPlayer = AVAudioPlayer(contentsOf: urlIntro)
        audioPlayer?.delegate = self
    }

    // AVAudioPlayer will call this func when the first song ends:
    func audioPlayerDidFinishPlaying(_ player: AVAudioPlayer, successfully flag: Bool) {
        // your 2nd do/catch code...
        try audioPlayer = AVAudioPlayer(contentsOf: url)
        audioPlayer?.delegate = self
    }

}

let player = Player()
player.startPlayingFirstSong()