Programmatically connect to paired Bluetooth speaker and play audio

Question

In our app, I'd like to connect to a previously paired A2DP Bluetooth Speaker and direct audio playback to it, using Android v4.2 or later.

I can successfully create an A2DP profile object using this code to start the process:

/* Manifest permissions */
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>

// Get the default adapter
BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

// Establish connection to the proxy.
mBluetoothAdapter.getProfileProxy(this, mProfileListener, BluetoothProfile.A2DP)

And the following listener to respond to the connection:

private BluetoothProfile.ServiceListener mProfileListener = new BluetoothProfile.ServiceListener() {
public void onServiceConnected(int profile, BluetoothProfile proxy) {

    if (profile == BluetoothProfile.A2DP) {

        mBluetoothSpeaker = (BluetoothA2dp) proxy;

        // no devices are connected         
        List<BluetoothDevice> connectedDevices = mBluetoothSpeaker.getConnectedDevices();

        //the one paired (and disconnected) speaker is returned here
        int[] statesToCheck = {BluetoothA2dp.STATE_DISCONNECTED};           
        List<BluetoothDevice> disconnectedDevices = mBluetoothSpeaker.getDevicesMatchingConnectionStates(statesToCheck);



        BluetoothDevice btSpeaker = disconnectedDevices.get(0); 

        //WHAT NOW?

    }
}
public void onServiceDisconnected(int profile) {
    if (profile == BluetoothProfile.A2DP) {
        mBluetoothSpeaker = null;
    }
}
};

I'm just a little lost as to what to do now, to connect the device, and direct the audio output to it. I've tried connecting to the device, as detailed in the Android docs, with the following code, but the final BluetoothSpeaker.getConnectedDevices() call returns no connected devices.

    BluetoothSocket tmp = null;
    UUID MY_UUID = UUID.fromString("00001108-0000-1000-8000-00805f9b34fb");
    try {           
        tmp = btSpeaker.createInsecureRfcommSocketToServiceRecord(MY_UUID);

    } catch (IOException e1) {
        // TODO Auto-generated catch block
        Log.d("createRfcommSocketToServiceRecord ERROR", e1.getMessage());
    }
    mmSocket = tmp;

    try {
        // Connect the device through the socket. This will block
        // until it succeeds or throws an exception
        mmSocket.connect();
    } catch (IOException connectException) {
        // Unable to connect; close the socket and get out
        try {
            Log.d("connectException", connectException.getMessage());
            mmSocket.close();
        } catch (IOException closeException) { }
        return;
    }

    connectedDevices = mBluetoothSpeaker.getConnectedDevices();

The code does seem to connect to the device in some way though, as when I stop execution, the Bluetooth speaker annouces that it is ready to pair (as it always does when it disconnects from an audio source).

Older versions of the BluetoothA2dp seem to have a connect(BluetoothDevice device) method, but that has now been removed (as of 4.2) and I'm struggling to find any clear examples of how to programmatically connect to an A2DP device, and to direct audio output to it. Any help on how to approach either would be gratefully received.

Any advice on how to approach this would be hugely appreciated.

I'm assuming you're creating your mProfileListener instance BEFORE calling getProfileProxy(...)? — Squonk
The answer to this question stackoverflow.com/questions/12542523/… and the comments on it don't seem promising. — Squonk
Thanks Squonk, I can get the device to connect (or at least fire a BluetoothDevice.ACTION_ACL_CONNECTED event) by calling createInsecureRfcommSocketToServiceRecord(), but if that post is right, then RFcomm is wrong for A2DP broadcasting anyway. What is the right way to connect to a device for A2DP? There seems to be a gaping hole in the Android Bluetooth documentation (or at least my understanding of it). — Ted
To be honest I don't know as I've never tried with A2DP but I agree there is a gap in the docs. It seems odd there are options for A2DP but no useful methods for using it (or at least no useful documentation explaining how to use it). If I come across anything I'll get back to you. — Squonk

zxshi zxshi · Accepted Answer · 2014-03-13T20:46:58

This one works for me. After receive BluetoothA2dp.STATE_CONNECTED, you can play music as normal.

public class A2DPActivity extends Activity {

protected static final String TAG = "ZS-A2dp";

Button mBtPlay;

BluetoothAdapter mBtAdapter;
BluetoothA2dp mA2dpService;

AudioManager mAudioManager;
MediaPlayer mPlayer;

BroadcastReceiver mReceiver = new BroadcastReceiver() {

    @Override
    public void onReceive(Context ctx, Intent intent) {
        String action = intent.getAction();
        Log.d(TAG, "receive intent for action : " + action);
        if (action.equals(BluetoothA2dp.ACTION_CONNECTION_STATE_CHANGED)) {
            int state = intent.getIntExtra(BluetoothA2dp.EXTRA_STATE, BluetoothA2dp.STATE_DISCONNECTED);
            if (state == BluetoothA2dp.STATE_CONNECTED) {
                setIsA2dpReady(true);
                playMusic();
            } else if (state == BluetoothA2dp.STATE_DISCONNECTED) {
                setIsA2dpReady(false);
            }
        } else if (action.equals(BluetoothA2dp.ACTION_PLAYING_STATE_CHANGED)) {
            int state = intent.getIntExtra(BluetoothA2dp.EXTRA_STATE, BluetoothA2dp.STATE_NOT_PLAYING);
            if (state == BluetoothA2dp.STATE_PLAYING) {
                Log.d(TAG, "A2DP start playing");
                Toast.makeText(A2DPActivity.this, "A2dp is playing", Toast.LENGTH_SHORT).show();
            } else {
                Log.d(TAG, "A2DP stop playing");
                Toast.makeText(A2DPActivity.this, "A2dp is stopped", Toast.LENGTH_SHORT).show();
            }
        }
    }

};

boolean mIsA2dpReady = false;
void setIsA2dpReady(boolean ready) {
    mIsA2dpReady = ready;
    Toast.makeText(this, "A2DP ready ? " + (ready ? "true" : "false"), Toast.LENGTH_SHORT).show();
}

private ServiceListener mA2dpListener = new ServiceListener() {

    @Override
    public void onServiceConnected(int profile, BluetoothProfile a2dp) {
        Log.d(TAG, "a2dp service connected. profile = " + profile);
        if (profile == BluetoothProfile.A2DP) {
            mA2dpService = (BluetoothA2dp) a2dp;
            if (mAudioManager.isBluetoothA2dpOn()) {
                setIsA2dpReady(true);
                playMusic();
            } else {
                Log.d(TAG, "bluetooth a2dp is not on while service connected");
            }
        }
    }

    @Override
    public void onServiceDisconnected(int profile) {
        setIsA2dpReady(false);
    }

};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    LinearLayout ll = new LinearLayout(this);
    setContentView(ll);

    mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
    registerReceiver(mReceiver, new IntentFilter(BluetoothA2dp.ACTION_CONNECTION_STATE_CHANGED));
    registerReceiver(mReceiver, new IntentFilter(BluetoothA2dp.ACTION_PLAYING_STATE_CHANGED));

    mBtAdapter = BluetoothAdapter.getDefaultAdapter();
    mBtAdapter.getProfileProxy(this, mA2dpListener , BluetoothProfile.A2DP);

}

@Override
protected void onDestroy() {
    mBtAdapter.closeProfileProxy(BluetoothProfile.A2DP, mA2dpService);
    releaseMediaPlayer();
    unregisterReceiver(mReceiver);
    super.onDestroy();
}

@Override
protected void onPause() {
    releaseMediaPlayer();
    super.onPause();
}

private void releaseMediaPlayer() {
    if (mPlayer != null) {
        mPlayer.release();
        mPlayer = null;
    }
}

private void playMusic() {
    mPlayer = new MediaPlayer();
    AssetManager assetManager = this.getAssets();
    AssetFileDescriptor fd;
    try {
        fd = assetManager.openFd("Radioactive.mp3");
        Log.d(TAG, "fd = " + fd);
        mPlayer.setDataSource(fd.getFileDescriptor());
        mPlayer.prepare();
        Log.d(TAG, "start play music");
        mPlayer.start();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

Programmatically connect to paired Bluetooth speaker and play audio

4 Answers