筆記Android — 監聽Line/WeChat網路電話和手機來電狀態切換TelephonyManager ＆ AudioFocusChangeListener

在音頻播放中可能會有來電導致中斷，在中斷回復後我們需要將使用者的音頻續撥，那該如何判斷來電狀態的切換呢？

手機來電使用TelephonyManager：

var telephoneManager = context.getSystemService(Service.TELEPHONY_SERVICE) as TelephonyManager
telephoneManager.listen(listener, PhoneStateListener.LISTEN_CALL_STATE)
//監聽方法
private val listener: PhoneStateListener = object : PhoneStateListener() {
    override fun onCallStateChanged(state: Int, number: String) {
        when (state) {
            TelephonyManager.CALL_STATE_IDLE -> {
                //狀態回復
            }
            TelephonyManager.CALL_STATE_RINGING -> {
                //偵測來電
            }
            else -> {
            }
        }
        super.onCallStateChanged(state, number)
    }
}

另外使用者也可能收到來自Line/WeChat/Messenger等網路電話，可以透過AudioFocus來監看Focus的變化：

//需要先設定我們的音頻屬性，這邊播放的內容Content type是Music，另外Usage就是一般Media的行為
val musicAudioAttributes = AudioAttributes.Builder().setContentType(AudioAttributes.CONTENT_TYPE_MUSIC).setUsage(AudioAttributes.USAGE_MEDIA).build()
val audioManager = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
audioManager.requestAudioFocus(AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN).setAudioAttributes(musicAudioAttributes).setAcceptsDelayedFocusGain(true).setOnAudioFocusChangeListener(onAudioFocusRequest).build()
//監看AudioFocus狀態變化
private val onAudioFocusRequest = AudioManager.OnAudioFocusChangeListener {
    when (it) {
        AudioManager.AUDIOFOCUS_GAIN -> {
            // We recovered audio focus.
        }
        AudioManager.AUDIOFOCUS_LOSS -> {
            // Lost focus for an unbounded amount of time
        }
        AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK -> {
            // Lost focus for a short time, but it's ok to keep playing at an attenuated level
        }
        AudioManager.AUDIOFOCUS_LOSS_TRANSIENT -> {
            // Lost focus for a short time
        }
    }
}

針對來電的測試思路比較細節，除了不同的來電來源還需測試各種情境：

如果A打給B，那可能測試情境如下
Case 1 : 電話撥通後A掛斷
Case 2 : 電話撥通後B掛斷
Case 3 : 電話撥通後B接起，A再掛斷
Case 4 : 電話撥通後B接起，B再掛斷