iOS中AVAudioPlayer连续播放失败：audioPlayerDidFinishPlaying未触发

问题描述 #

需要按顺序播放三段音频：getReady→nextExercise→burpees，预期流程：

• 在WorkoutTabataViewController中调用playGetReady()
• 播放第一段音频
• 音频播放结束后自动触发audioPlayerDidFinishPlaying()
• 调用playNextSound()播放下一段音频

实际问题：仅第一段音频播放，且audioPlayerDidFinishPlaying()未被触发，相关代码如下：

class AudioPlayerManager: AVAudioPlayerDelegate {
    var description: String
    
    static let shared = AudioPlayerManager()
    var audioPlayer: AVAudioPlayer?
    var workoutVC: WorkoutTabataViewController?
    var mainVC: MainTabataViewController?
    
    var currentSound = 0
    let urls: [URL]
    
    init() {
        self.description = ""
        //First sound
        let getReady = Bundle.main.path(forResource: "Get ready", ofType: "mp3")!
        let urlGetReady = URL(fileURLWithPath: getReady)
        
        //Second sound
        let nextExercise = Bundle.main.path(forResource: "Next Exercise", ofType: "mp3")!
        let urlNextExercise = URL(fileURLWithPath: nextExercise)
        
        //Third sound
        let burpees = Bundle.main.path(forResource: "Burpees", ofType: "mp3")!
        let urlBurpees = URL(fileURLWithPath: burpees)
        
        urls = [urlGetReady, urlNextExercise, urlBurpees]
    }
    
    func playGetReady() {

        do {
            audioPlayer = try AVAudioPlayer(contentsOf: urls[currentSound])
            audioPlayer?.delegate = self
            audioPlayer?.play()
        } catch {
            print(error)
        }
    }
    
    func playNextSound() {
        currentSound += 1

        if currentSound < urls.count {
            do {
                audioPlayer = try AVAudioPlayer(contentsOf: urls[currentSound])
                audioPlayer?.delegate = self
                audioPlayer?.play()
            } catch {
                print(error)
            }
        }
    }
    
    func audioPlayerDidFinishPlaying(_ player: AVAudioPlayer, successfully flag: Bool) {
 
        if flag {
            playNextSound()
        }
    }
}

问题根源 #

1. 未配置音频会话：AVAudioPlayer的播放完成回调依赖活跃的AVAudioSession，未初始化激活会话会导致系统无法传递播放完成信号。
2. 未继承NSObject：AVAudioPlayerDelegate是Objective-C协议，Swift类必须继承NSObject才能正确响应代理回调。
3. 播放索引未重置：多次调用playGetReady()时，currentSound保留之前数值会导致播放顺序混乱（虽不是当前回调失效直接原因，但属于潜在问题）。

解决方案 #

修正后的代码如下，解决了所有问题：

import AVFoundation

class AudioPlayerManager: NSObject, AVAudioPlayerDelegate {
    var description: String
    
    static let shared = AudioPlayerManager()
    var audioPlayer: AVAudioPlayer?
    var workoutVC: WorkoutTabataViewController?
    var mainVC: MainTabataViewController?
    
    var currentSound = 0
    let urls: [URL]
    
    // 私有化初始化，保证单例唯一性
    private override init() {
        self.description = ""
        // 初始化音频URL
        let getReady = Bundle.main.path(forResource: "Get ready", ofType: "mp3")!
        let urlGetReady = URL(fileURLWithPath: getReady)
        
        let nextExercise = Bundle.main.path(forResource: "Next Exercise", ofType: "mp3")!
        let urlNextExercise = URL(fileURLWithPath: nextExercise)
        
        let burpees = Bundle.main.path(forResource: "Burpees", ofType: "mp3")!
        let urlBurpees = URL(fileURLWithPath: burpees)
        
        urls = [urlGetReady, urlNextExercise, urlBurpees]
        super.init()
        
        // 初始化并激活音频会话
        setupAudioSession()
    }
    
    private func setupAudioSession() {
        let session = AVAudioSession.sharedInstance()
        do {
            // 设置音频会话为播放模式
            try session.setCategory(.playback, mode: .default)
            // 激活音频会话
            try session.activate()
        } catch {
            print("音频会话初始化失败: \(error)")
        }
    }
    
    func playGetReady() {
        currentSound = 0 // 重置播放索引，确保每次调用从第一段开始
        guard currentSound < urls.count else { return }
        
        do {
            audioPlayer = try AVAudioPlayer(contentsOf: urls[currentSound])
            audioPlayer?.delegate = self
            audioPlayer?.play()
        } catch {
            print("播放音频失败: \(error)")
        }
    }
    
    func playNextSound() {
        currentSound += 1

        guard currentSound < urls.count else { return }
        
        do {
            audioPlayer = try AVAudioPlayer(contentsOf: urls[currentSound])
            audioPlayer?.delegate = self
            audioPlayer?.play()
        } catch {
            print("播放下一段音频失败: \(error)")
        }
    }
    
    func audioPlayerDidFinishPlaying(_ player: AVAudioPlayer, successfully flag: Bool) {
        guard flag else { return }
        playNextSound()
    }
}

关键修正点说明 #

• 继承NSObject：确保Swift类能正确响应Objective-C代理回调
• 初始化音频会话：激活播放模式会话是触发audioPlayerDidFinishPlaying回调的核心前提
• 重置播放索引：每次调用playGetReady()时重置索引，避免重复调用导致的播放位置错误
• 私有化初始化：严格保证单例唯一实例，避免意外创建多个管理实例

内容的提问来源于stack exchange，提问作者Ростислав Григорьев