void initEditFieldActions() {
		if (getModel() == null)
			throw new NullPointerException("model is null");
		Action a = new EditGFieldAction(getModel());
		getModel().getActions().put(a.toString(), a);
		getActionMap().put("Edit Gravitational Field", a);
		a = new EditEFieldAction(getModel(), false);
		getModel().getActions().put(a.toString(), a);
		getActionMap().put("Edit Electric Field", a);
		a = new EditBFieldAction(getModel(), false);
		getModel().getActions().put(a.toString(), a);
		getActionMap().put("Edit Magnetic Field", a);
	}