当活动不是父级时，我们如何在片段和活动之间实现共享视图模型通信

class SharedViewModel : ViewModel() {
    private val _data = MutableLiveData<String>()
    val data: LiveData<String> get() = _data

    fun updateData(newData: String) {
        _data.value = newData
    }
}

class FragmentA : Fragment() {
    private lateinit var viewModel: SharedViewModel

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_a, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel = ViewModelProvider(requireActivity()).get(SharedViewModel::class.java)

        viewModel.data.observe(viewLifecycleOwner, Observer { data ->
            // Update UI with the new data
        })

        // Example of updating data
        viewModel.updateData("Hello from FragmentA")
    }
}

class FragmentB : Fragment() {
    private lateinit var viewModel: SharedViewModel

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_b, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel = ViewModelProvider(requireActivity()).get(SharedViewModel::class.java)

        viewModel.data.observe(viewLifecycleOwner, Observer { data ->
            // Update UI with the new data
        })
    }
}