MainFragment.java

public class MainFragment extends Fragment {
  
    ...
      
    // 1 - Create a disposable
    private Disposable disposable;
  
    @Override
    public void onDestroy() {
        // 2 - Unsubscribe 
        if (this.disposable != null) this.disposable.dispose();
        super.onDestroy();
    }  
    ...
}