Android请求音频焦点

申请音频焦点 

private var mAudioFocusRequest: AudioFocusRequest? = null
    private fun requestAudioFocus() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            if (mAudioFocusRequest == null) {
                val attr = AudioAttributes.Builder()
                    .setUsage(AudioAttributes.USAGE_MEDIA)
                    .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
                    .build()
                mAudioFocusRequest = AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN)
                    .setAudioAttributes(attr)
                    .setOnAudioFocusChangeListener(this)
                    .build()
            }
            mAudioFocusRequest?.apply {
                (App.instance.getSystemService(Context.AUDIO_SERVICE) as AudioManager).let { manager ->
                    manager.requestAudioFocus(this).let {
                        when (it) {
                            AudioManager.AUDIOFOCUS_REQUEST_FAILED -> {
                                // 申请焦点失败
                            }
                            AudioManager.AUDIOFOCUS_REQUEST_GRANTED -> {
                                // 申请成功
                            }
                            AudioManager.AUDIOFOCUS_REQUEST_DELAYED -> {
                                // 稍后获取
                            }
                        }
                    }
                }
            }
        } else {
            (App.instance.getSystemService(Context.AUDIO_SERVICE) as AudioManager).requestAudioFocus(
                this,
                AudioManager.STREAM_MUSIC,
                AudioManager.AUDIOFOCUS_GAIN
            )
        }
    }

放弃音频焦点 

private var mAudioFocusRequest: AudioFocusRequest? = null
    private fun abandonAudioFocus() {
        mAudioFocusRequest?.apply {
            (App.instance.getSystemService(Context.AUDIO_SERVICE) as AudioManager)
                .abandonAudioFocusRequest(this)
        }
        mAudioFocusRequest = null
    }

音频焦点变化监听

override fun onAudioFocusChange(focusChange: Int) {
        // 拍摄视频：>-2>1
        when (focusChange) {
            AudioManager.AUDIOFOCUS_GAIN -> {
                // 长时间持有焦点
            }
            AudioManager.AUDIOFOCUS_GAIN_TRANSIENT -> {
                // 暂时焦点
            }
            AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK -> {
                // 共享焦点，其他音频降低
            }
            AudioManager.AUDIOFOCUS_LOSS -> {
                // 长时间失去焦点
            }
            AudioManager.AUDIOFOCUS_LOSS_TRANSIENT -> {
                // 暂时失去焦点
            }
        }
    }