Setting default argument for an extended class

I am making an application that involves create/retrieve/update/delete operations.

So for the add and edit method I want to re-use core components that are the same in both functions. So I made a shared abstract class and then my add and edit classes extend the shared so they each have the same core but can still have differences.

I instantiate these objects/Fragments by using the newInstance method, which is where I usually pass in arguments, set them into the Bundle, and then read them back in the onCreateView methods.

However I need to be able to pull in arguments to the shared class, but I can't because it's abstract, and when I instantiate the objects, I am instantiating Edit and Add objects, which means only the child classes can have arguments.

What's the accepted practice for getting around this?

public abstract class SharedStuffDialogFragment extends DialogFragment {
    protected MyObject mMyObject; //I'd like to be able to init. this

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View contentView = inflater.inflate(R.layout.shared_layout, container, false);

        //do a bunch of other stuff here, sharable attributes
        initOtherThings(savedInstanceState);
        return contentView;
    }

    protected abstract void initOtherThings(Bundle savedInstanceState);


}

And then for example, the add class:

public class AddDialogFragment extends SharedStuffDialogFragment {
    private static final String ARGUMENT_OBJECT = "argument_object";
    private MyObject mMyObject;

    public static AddDialogFragment newInstance(MyObject object) {
        Bundle args = new Bundle();
        args.putParcelable(ARGUMENT_OBJECT, object); //would really rather set this to shared
        AddDialogFragment fragment = new AddDialogFragment();
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    protected void initOtherThings(Bundle savedInstanceState) {
        mMyObject = getArguments().getParcelable(ARGUMENT_OBJECT);
        //do stuff unique to add operations
    }

}