如何使用SharedViewModel在活动和片段之间共享数据？

public class SharedViewModel extends ViewModel {
    private MutableLiveData<String> sharedData = new MutableLiveData<>();

    public void setSharedData(String data) {
        sharedData.setValue(data);
    }

    public LiveData<String> getSharedData() {
        return sharedData;
    }
}

public class MainActivity extends AppCompatActivity {
    private SharedViewModel sharedViewModel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        sharedViewModel = new ViewModelProvider(this).get(SharedViewModel.class);

        sharedViewModel.getSharedData().observe(this, new Observer<String>() {
            @Override
            public void onChanged(String data) {
                // 处理共享数据的变化
            }
        });
    }
}

public class MyFragment extends Fragment {
    private SharedViewModel sharedViewModel;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        sharedViewModel = new ViewModelProvider(requireActivity()).get(SharedViewModel.class);
    }

    private void setSharedData(String data) {
        sharedViewModel.setSharedData(data);
    }

    private LiveData<String> getSharedData() {
        return sharedViewModel.getSharedData();
    }
}