MediaPlayer无法在Android Things Raspberry Pi 3上运行

Question

我只是想尝试使用MediaPlayer播放声音。下面的代码适用于常规Android项目，通过音频插孔或HDMI监视器的扬声器播放声音。

final MediaPlayer mp = MediaPlayer.create(getActivity(), R.raw.score);
mp.setOnErrorListener(new MediaPlayer.OnErrorListener() {
    @Override
    public boolean onError(MediaPlayer mp, int what, int extra) {
        return false;
    }
});
mp.start();

我接近这个错误的方式吗？ MediaPlayer类不能以这种方式使用Android Things吗？

更新1

作为替代方法，我也尝试使用AudioTrack播放声音，这也不起作用：

    int i = 0;
    byte[] music = null;
    InputStream is = getActivity().getResources().openRawResource(R.raw.score);

    AudioTrack at = new AudioTrack(AudioManager.STREAM_MUSIC, 44100,
            AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT,
            AudioTrack.getMinBufferSize(44100,
                    AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT), AudioTrack.MODE_STREAM);

    try{
        music = new byte[512];
        at.play();

        while((i = is.read(music)) != -1)
            at.write(music, 0, i);

    } catch (IOException e) {
        e.printStackTrace();
    }

    at.stop();
    at.release();

更新2

建议设置首选设备。这也行不通。

mAudioOutputDevice = findAudioDevice(AudioManager.GET_DEVICES_OUTPUTS, AudioDeviceInfo.TYPE_BUILTIN_SPEAKER);

获取设备

private AudioDeviceInfo findAudioDevice(int deviceFlag, int deviceType) {
    AudioManager manager = (AudioManager) getActivity().getSystemService(Context.AUDIO_SERVICE);
    AudioDeviceInfo[] adis = manager.getDevices(deviceFlag);
    for (AudioDeviceInfo adi : adis) {
        if (adi.getType() == deviceType) {
            return adi;
        }
    }
    return null;
}

这里我设置了首选设备。

    int i = 0;
    byte[] music = null;
    InputStream is = getActivity().getResources().openRawResource(R.raw.score);

    AudioTrack at = new AudioTrack(AudioManager.STREAM_MUSIC, 44100,
            AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT,
            AudioTrack.getMinBufferSize(44100,
                    AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT), AudioTrack.MODE_STREAM);
    at.setPreferredDevice(mAudioOutputDevice);

    try{
        music = new byte[512];
        at.play();

        while((i = is.read(music)) != -1)
            at.write(music, 0, i);

    } catch (IOException e) {
        e.printStackTrace();
    }

    at.stop();
    at.release();

Answer 1

我能够使用MediaPlayer类和USB 2.0外部立体声适配器播放声音（如下所示）。只需将适配器连接到Raspberry Pi上的空USB插槽，并将音频输入连接到适配器即可。

final MediaPlayer mp = MediaPlayer.create(getActivity(), R.raw.score);
mp.start();

Answer 2

您可能需要指定要将声音发送到的音频总线：

private AudioDeviceInfo findAudioDevice(int deviceFlag, int deviceType) {
    AudioManager manager = (AudioManager) this.getSystemService(Context.AUDIO_SERVICE);
    AudioDeviceInfo[] adis = manager.getDevices(deviceFlag);
    for (AudioDeviceInfo adi : adis) {
        if (adi.getType() == deviceType) {
            return adi;
        }
    }
    return null;
}

然后找到音频插孔总线：

mAudioInputDevice = findAudioDevice(AudioManager.GET_DEVICES_INPUTS, AudioDeviceInfo.TYPE_BUILTIN_MIC);
mAudioOutputDevice = findAudioDevice(AudioManager.GET_DEVICES_OUTPUTS, AudioDeviceInfo.TYPE_BUILTIN_SPEAKER);

然后您可以运行audioTrack.setPreferredDevice(mAudioOutputDevice);