用LiveData和Repository设置ViewModel的正确方法

class MyRepository(private val apiService: ApiService) {

    private val _data = MutableLiveData<MyData>()
    val data: LiveData<MyData> get() = _data

    fun fetchData() {
        apiService.getData().enqueue(object : Callback<MyData> {
            override fun onResponse(call: Call<MyData>, response: Response<MyData>) {
                if (response.isSuccessful) {
                    _data.postValue(response.body())
                }
            }

            override fun onFailure(call: Call<MyData>, t: Throwable) {
                // Handle failure
            }
        })
    }
}

class MyViewModel(private val repository: MyRepository) : ViewModel() {

    val data: LiveData<MyData> = repository.data

    fun fetchData() {
        repository.fetchData()
    }
}

class MyActivity : AppCompatActivity() {

    private lateinit var viewModel: MyViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_my)

        val apiService = Retrofit.Builder()
            .baseUrl("https://api.example.com/")
            .addConverterFactory(GsonConverterFactory.create())
            .build()
            .create(ApiService::class.java)

        val repository = MyRepository(apiService)
        viewModel = ViewModelProvider(this, object : ViewModelProvider.Factory {
            override fun <T : ViewModel?> create(modelClass: Class<T>): T {
                return MyViewModel(repository) as T
            }
        }).get(MyViewModel::class.java)

        viewModel.data.observe(this, Observer { myData ->
            // Update UI with myData
        })

        viewModel.fetchData()
    }
}