Swift｜Headphone Unplug Detectionと自動停止のしくみ｜イヤホン抜け検知

import AVFoundation

final class AudioSessionManager {
    private let nc = NotificationCenter.default
    var onHeadphoneUnplugged: (() -> Void)?

    func activate() throws {
        let s = AVAudioSession.sharedInstance()
        try s.setCategory(.playback, options: [.mixWithOthers])
        try s.setActive(true)
        observeRouteChange()
    }

    private func observeRouteChange() {
        nc.addObserver(forName: AVAudioSession.routeChangeNotification,
                       object: nil, queue: .main) { [weak self] note in
            guard let self,
                  let info = note.userInfo,
                  let reasonRaw = info[AVAudioSessionRouteChangeReasonKey] as? UInt,
                  let reason = AVAudioSession.RouteChangeReason(rawValue: reasonRaw)
            else { return }

            // 旧ルート（抜けたデバイスを知る）
            let prev = info[AVAudioSessionRouteChangePreviousRouteKey]
                        as? AVAudioSessionRouteDescription

            if reason == .oldDeviceUnavailable,
               let outputs = prev?.outputs {
                let wasHeadphones = outputs.contains { out in
                    out.portType == .headphones ||
                    out.portType == .bluetoothA2DP ||
                    out.portType == .bluetoothHFP ||
                    out.portType == .bluetoothLE
                }
                if wasHeadphones {
                    onHeadphoneUnplugged?() // ここで停止/フェードダウンなどを行う
                }
            }
        }
    }
}

// LocalAudioEngine.swift 側
engineSession.onHeadphoneUnplugged = { [weak self] in
    self?.fade(to: 0.0, duration: 0.4) { [weak self] in
        self?.stop()
        // 必要ならUIへ「イヤホンが外れたため停止しました」を通知
    }
}