Sending java object from Android Plugin to Unity

Hello, I am developing a plugin for Android using the eclipse environment and packing the library as .jar file. I have been reading that there is the possibility to use the sendMessage function to communicate to Unity function from Java.
My problem is that I have some async tasks which I want to notify from the Java code to Unity and I have read that the sendMessage option is really expensive in terms of CPU. I need to send messages quite often because the plugin consists of a BluetoothManager sending the positions and other info of the GameObjects.
Does anyone know if there is any other option to notify and send objects from Java code to Unity?

Thanks in advance

Regards, Javi.

Any idea about that please?

I’m also looking for an answer to this

@jlpjavi Did you manage to solve it?