Get list of connected Bluetooth LE devices

Question

I am new to the Bluetooth Low Energy (LE) API. Is there a way to check if the Android device is currently connected to any Bluetooth LE devices and possibly get a list of those devices?

Do BT-LE devices even actually "connect"? I noticed when my smartwatch is paired/connected with my Nexus 5, the Bluetooth icon does not become white/bold in the status bar (on KitKat), like it does when connected to a classic Bluetooth device.

I was using the code below for classic devices. It looks like I can check GATT and GATT_SERVER the same way but they always return disconnected.

UPDATE: So now that I have flashed Android Lollipop to my Nexus 5, I see it must be possible somehow, because it is used for SmartLock, and it somehow detects my BT-LE Android watch as being connected.

private BluetoothAdapter getBTAdapter() {       
    if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.JELLY_BEAN_MR2)
        return BluetoothAdapter.getDefaultAdapter();
    else {
        BluetoothManager bm = (BluetoothManager) context.getSystemService(Context.BLUETOOTH_SERVICE);
        return bm.getAdapter();
    }
}

public boolean isBluetoothConnected() {
    if(mBluetoothAdapter == null || 
            (mBluetoothAdapter.getProfileConnectionState(BluetoothProfile.HEADSET) == BluetoothProfile.STATE_DISCONNECTED 
                && mBluetoothAdapter.getProfileConnectionState(BluetoothProfile.A2DP) == BluetoothProfile.STATE_DISCONNECTED
                && mBluetoothAdapter.getProfileConnectionState(BluetoothProfile.HEALTH) == BluetoothProfile.STATE_DISCONNECTED)

            ) {

        Utils.logDebug(TAG, "GATT_SERVER " + mBluetoothAdapter.getProfileConnectionState(BluetoothProfile.GATT_SERVER));
        Utils.logDebug(TAG, "GATT " + mBluetoothAdapter.getProfileConnectionState(BluetoothProfile.GATT));
        return false;
    }
    return true;
}

Answer 1

You can use this:

BluetoothManager bluetoothManager = (BluetoothManager) mContext.getSystemService(Context.BLUETOOTH_SERVICE);
List<BluetoothDevice> devices = bluetoothManager.getConnectedDevices(BluetoothProfile.GATT);
for(BluetoothDevice device : devices) {
  if(device.getType() == BluetoothDevice.DEVICE_TYPE_LE) {
     ...
  }
}

I can not answer if your watch is actually connected . May be your watch advertises only its state and the phone is listening for this advertisements. It depends how it is implemented.