Check Bluetooth State on specific device on android

Question

I'm trying to know at my application start up if a paired device is connect or not. In practice the main app give me an MAC address and I've got to respond if we're connected or not.

A BroadcastReceiver can't be a full option because if the user start the connection with the device before launching the app I'll be unable to know if I'm connect to the device or not.

I found this on the forum : How to programmatically tell if a Bluetooth device is connected?

There is no way to retrieve the list of connected devices at application startup. The Bluetooth API will only let you listen to connection changes.

but i think this isn't accurate anymore because with this code :

public class cServiceListener  implements BluetoothProfile.ServiceListener  {
private static final int[] states={ BluetoothProfile.STATE_DISCONNECTING,
        BluetoothProfile.STATE_DISCONNECTED,
        BluetoothProfile.STATE_CONNECTED,
        BluetoothProfile.STATE_CONNECTING};
@RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN_MR2)
@Override
public void onServiceConnected(int profile, BluetoothProfile bluetoothProfile) {


    //List<BluetoothDevice> Devices=bluetoothProfile.getDevicesMatchingConnectionStates(states);
    BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    Set<BluetoothDevice> devices = mBluetoothAdapter.getBondedDevices();

    Log.i("myTag","\n\n<==============profile connexion state =============> : "+ mBluetoothAdapter.getProfileConnectionState(1));

    for (BluetoothDevice loop:devices){
        Log.i("myTag","Nom du device :" +loop.getName()+" Etat du Device:"+bluetoothProfile.getConnectionState(loop)
        + "  Type du device : "+ loop.getType() + " Classe du device : " + loop.getBluetoothClass().toString() );
    }
}

@Override
public void onServiceDisconnected(int profile) {
}}

I'm able to tell if SOME devices are connected or not but not with all of them !! I try the code with portable speakers and with others devices where the calls AND the sounds is take in charge and it work perfectly : if the device is connect it return 2 and if not it return 0. But when i try it on my real objective (which is a car) it return 0 at anytime. The test car only take in charge calls (you can't play your music with Bluetooth connection, to old). So I think with more modern car it can work..

First i was thinking that car using BLE technology so I try with this code

         List<BluetoothDevice> devices = bluetoothManager.getConnectedDevices(BluetoothProfile.GATT);
            Log.d("myTag","\n Taille de la liste : " + devices.size());
            for(BluetoothDevice device : devices) {

                if(device.getType() == BluetoothDevice.DEVICE_TYPE_LE) {
                    Log.d("myTag","\n BLE <===> Nom du device :" + device.getName());
                }
                Log.d("myTag","\n<====NONE BLE=====> // \n\n Nom du device :" + device.getName()+"\n\n");
            }

But in fact this isn't the point, this don't work. And it's weird because

 mBluetoothAdapter.getProfileConnectionState(1)

returning the correct value when I'm connect to the car only. I really don't know what to do know and why bluetoothProfile.getConnectionState() returning the wrong value. If someone have any idea, I'll be glad to know.

Answer 1

Finally I've achived the work. Bluetooth car are considere like headset so I focus on it :

public static void startListening() {
final BroadcastReceiver mBroadcastReceiver3 = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        Bundle info = intent.getExtras();
        BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
        String deviceAddress =  device.getAddress();
        if (action.equals( BluetoothDevice.ACTION_ACL_CONNECTED)){
            //do some stuff with connected device
        }
        if (action.equals(BluetoothDevice.ACTION_ACL_DISCONNECTED)){
            // do things with disconnected
        }
    }
};}