如何指定内部扬声器来播放音频文件？

Question

在我的Android应用程序中，我想在手机内部扬声器上播放声音，即使用户通过蓝牙设备或其他外部扬声器连接到设备上。这能办到吗？

Answer 1

我想出了在电话扬声器上播放音频的方法，即使我有一个连接的蓝牙音频设备：

fun createPhoneSpeakerPreferredPlayer(context: Context, resource: Int): MediaPlayer{
    val mediaPlayer = MediaPlayer.create(context, resource)
    val audioDeviceType = if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) AudioDeviceInfo.TYPE_BUILTIN_SPEAKER_SAFE else AudioDeviceInfo.TYPE_BUILTIN_SPEAKER
    val audioManager = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
    val devices = audioManager.getDevices(AudioManager.GET_DEVICES_OUTPUTS)
    //create mapped devices variable to allow better logging.  The devices collection is not being serialized well (or at all)
    val mappedDevices = (devices.map {
        @Suppress("unused")
        object {
        val id = it.id
        val type = it.type
        val productName = it.productName
    }})
    val jsonRepresentation = Gson().toJson(mappedDevices)
    Log.d(Tag, "devices: $jsonRepresentation")
    val playbackDevice = devices.firstOrNull { it.type == audioDeviceType }
    Log.d(Tag, "selectedDevice: {id=${playbackDevice?.id}}, type=\"${playbackDevice?.type}\", productName=\"${playbackDevice?.productName}\"")
    mediaPlayer.preferredDevice = playbackDevice
    return mediaPlayer
}

要使用该方法并播放音频：

val mediaPlayer = createPhoneSpeakerPreferredPlayer(this.context, R.raw.myAudioId)
mediaPlayer.looping = true
mediaPlayer.start()

如果我连接了蓝牙扬声器，这似乎是可行的，但一旦我开始在后台播放音频，比如观看Netflix，或收听播客，这些音频就不再在电话扬声器上播放。

下面是我用两个按钮制作的一个示例应用程序。一个通过电话扬声器播放音乐，另一个通过任何连接的扬声器播放：

https://github.com/danwize/play-sound-android/blob/main/SoundPlayer/app/src/main/java/com/example/soundplayer/MainActivity.kt

我看到，当我第一次创建一个媒体播放器并以这种方式播放声音时，声音确实会在电话扬声器上播放。第二个音频在蓝牙扬声器上播放。当我没有播放任何视频或音乐，但仍然连接到蓝牙设备时，我的声音都会在电话扬声器上播放。以下是显示我正确设置首选设备的日志：

2022-09-07 11:21:33.969 6101-6101/com.myApp D/MediaPlayerExtensions: devices: [{"id":2,"productName":"Pixel 3","type":1},{"id":3,"productName":"Pixel 3","type":2},{"id":11,"productName":"Pixel 3","type":18},{"id":369,"productName":"Jabra Elite 85h","type":8},{"id":363,"productName":"Jabra Elite 85h","type":7}]
2022-09-07 11:21:33.969 6101-6101/com.myApp D/MediaPlayerExtensions: selectedDevice: {id=3}, type="2", productName="Pixel 3"
2022-09-07 11:22:14.290 6101-6101/com.myApp D/MediaPlayerExtensions: devices: [{"id":2,"productName":"Pixel 3","type":1},{"id":3,"productName":"Pixel 3","type":2},{"id":11,"productName":"Pixel 3","type":18},{"id":369,"productName":"Jabra Elite 85h","type":8},{"id":363,"productName":"Jabra Elite 85h","type":7}]
2022-09-07 11:22:14.290 6101-6101/com.myApp D/MediaPlayerExtensions: selectedDevice: {id=3}, type="2", productName="Pixel 3"