Swift AVAudioPlayer 的播放状态始终为 true？

Question

这是我的代码：

@objc func playSmusic1() {
        guard let url = Bundle.main.url(forResource: "Snote6", withExtension: "wav") else { return }
        do {
            try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
            try AVAudioSession.sharedInstance().setActive(true)
            player = try AVAudioPlayer(contentsOf: url, fileTypeHint: AVFileType.wav.rawValue)
            guard let player = player else { return }
            while (true) {
                player.play()
                player.enableRate = true;
                player.rate = playrate
                if !player.isPlaying {
                    break
                }
            }
        } catch let error {
            print(error.localizedDescription)
        }
    }

我发现 player.isPlaying 属性总是正确的，所以有时一个音调会播放 2 或 3 次。 如何修复这个错误？ 非常感谢！

Answer 1

第一：不要使用while(true)进行检查，因为它会阻塞主线程！

您应该添加 KVO 观察器以异步检查此属性，例如：

class YourController : UIViewController {
    var player: AVAudioPlayer?
    //...
    
    deinit {
        player?.removeObserver(self, forKeyPath: #keyPath(AVAudioPlayer.isPlaying))
    }

    func play() {
        //...
        player?.addObserver(self,
            forKeyPath: #keyPath(AVAudioPlayer.isPlaying),
            options: .new,
            context: nil)
        player?.play()
    }
    
    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if keyPath == #keyPath(AVAudioPlayer.isPlaying) {
            if let isPlaying = player?.isPlaying {
                print(isPlaying)
            }
        }
        else {
            self.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
        }
    }
}