Toggling A2DP Device (Android)

Question

I have two paired bluetooth devices (my car's head-unit for phone audio and a separate bluetooth receiver for A2DP). On my phone there's a checkbox for "Use for media audio" that I have to manually toggle for my A2DP output to go to my car's speakers. My goal is to toggle this programmatically.

I tried using both the AudioManager class with the deprecated setBluetoothA2dpOn and the setBluetoothScoOn but neither seemed to have any effect. I was able to get a list of the bluetooth paired devices and get a handle to the connection I want to toggle but I couldn't seem to get it quite right. I also tried getting the default bluetooth adapter and then using getProfileProxy but I feel like I'm barking up the wrong tree there.

Can anyone point me in the right direction? Basically all I want to do is the equivalent of checking that "Use for media audio" box.

Answer 1

A short time ago I had a similar problem trying connect a bluetooth device to android phone. Although your device profile being different, I think the solution is the same.

First you need create a package in your project named android.bluetooth and put the following IBluetoothA2dp.aidl in there:

package android.bluetooth;

import android.bluetooth.BluetoothDevice;

/**
 * System private API for Bluetooth A2DP service
 *
 * {@hide}
 */
interface IBluetoothA2dp {
    boolean connectSink(in BluetoothDevice device);
    boolean disconnectSink(in BluetoothDevice device);
    boolean suspendSink(in BluetoothDevice device);
    boolean resumeSink(in BluetoothDevice device);
    BluetoothDevice[] getConnectedSinks(); 
    BluetoothDevice[] getNonDisconnectedSinks();
    int getSinkState(in BluetoothDevice device);
    boolean setSinkPriority(in BluetoothDevice device, int priority);
    int getSinkPriority(in BluetoothDevice device);

    boolean connectSinkInternal(in BluetoothDevice device);
    boolean disconnectSinkInternal(in BluetoothDevice device);
}

Then, to access those functionalities, put the following class in your project:

public class BluetoothA2dpConnection {

private IBluetoothA2dp mService = null;

public BluetoothA2dpConnection() {

    try {
        Class<?>  classServiceManager = Class.forName("android.os.ServiceManager");
        Method methodGetService = classServiceManager.getMethod("getService", String.class);
        IBinder binder = (IBinder) methodGetService.invoke(null, "bluetooth_a2dp");
        mService = IBluetoothA2dp.Stub.asInterface(binder); 
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (SecurityException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    }
}

public boolean connect(BluetoothDevice device) {
    if (mService == null || device == null) {
        return false;
    }
    try {
        mService.connectSink(device);
    } catch (RemoteException e) {
        e.printStackTrace();
        return false;
    }
    return true;
}

public boolean disconnect(BluetoothDevice device) {
    if (mService == null || device == null) {
        return false;
    }
    try {
        mService.disconnectSink(device);
    } catch (RemoteException e) {
        e.printStackTrace();
        return false;
    }
    return true;
}

}

Finally, to connect your A2dp device, pick one BluetoothDevice from a list of paired devices and send it as parameter of connect method. Be sure to pick a device with the correct profile, otherwise you will have an exception.

I have tested this solution in a phone with android version 2.3 and it worked fine.

Sorry any English mistake. I hope this can help you.