按照文档进行操作，并记住使用相同的ViewModelStoreOwner，如下所示：

public class SharedViewModel extends ViewModel {

}

public class FragmentA extends Fragment {
    private SharedViewModel model;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //pass the host Activity
        model = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);
    }
}

public class FragmentB extends Fragment {
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
         //pass the host Activity
        SharedViewModel model = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);
    }
}