getBluetoothService called with no BluetoothManagerCallback

By reading into the Android source code, it seems to be a warning you cannot do anything about. The source code shows that if you call

BluetoothSocket#connect();

Then it will call

BluetoothAdapter.getDefaultAdapter().getBluetoothService(null);

The key here, is the null parameter that it passes in the above line. Due to this, there will be no callback, and then the BluetoothSocket class will throw out a warning.

Since it is only a warning, I do not think you need to do anything about it.

https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/bluetooth/BluetoothSocket.java line 306 https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/bluetooth/BluetoothAdapter.java line 1610

It appears that this gets called when multiple bluetooth sockets are opened at once. I fixed this by ensuring I was only opening 1 socket at a time.